A Sea Without Fish-- Life in the Ordovician Sea of the Cincinnai Region

A SEA WITHOUT FISH LIFE IN THE ORDOVICIAN SEA OF THE CINCINNATI REGION David L. Meyer and Richard Arnold Davis With a ...

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A SEA WITHOUT FISH LIFE IN THE ORDOVICIAN SEA OF THE CINCINNATI REGION

David L. Meyer and Richard Arnold Davis With a chapter by Steven M. Holland

Indiana

University

Bloomington

C?

Press Indianapolis

This book is a publication of Indiana 601

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Holland

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Data

Meyer, David L. A sea without fish: life in the Ordovician sea of the Cincinnati region / David L.

Meyer and Richard Arnold Davis; with a chapter by Steven M.

p. cm. — Includes ISBN 2.

bibliographical

978-0-253-35198-2

references (cloth:

and

alk.

Fossils—Ohio—Cincinnati Region.

index.

paper) I.

Davis,

1. R. A.

II. Title. QE726. 2. M49 560'.

2008

17310977178—dc22 2008020036

1

2 3 4 5

14

Holland.

(Life of the past)

13

12

11

10 09

Paleontology—Ordovician. (Richard Arnold),

date-

The w o r l d w i d e f a m e o f t h e fossils a n d r o c k s o f t h e C i n c i n n a t i , O h i o , reg i o n g r e w o u t o f the labors o f m y r i a d a m a t e u r fossil c o l l e c t o r s . T h e c u r r e n t e m b o d i m e n t of those folk is t h e " D r y D r e d g e r s , " a g r o u p f o u n d e d in C i n c i n n a t i in 1942 a n d , to this day, d e d i c a t e d to c o l l e c t i n g a n d u n d e r s t a n d i n g t h o s e fossils.

W e d e d i c a t e this v o l u m e t o t h e " D r y D r e d g e r s " a n d t o t h e h o s t o f fossil collectors they represent.

Vos salukimus!

CONTENTS

ix xiil

PREFACE ACKNOWLEDGMENTS

xv REPOSITORIES OF FOSSILS ILLUSTRATED IN THIS BOOK

1 Introduction 1

1 cm long) and high a b u n d a n c e in single beds of f i n e - g r a i n e d l i m e s t o n e . T h e o c c u r r e n c e o f l e p e r d i t i c o p i d s i s restricted t o f i n e - g r a i n e d l i m e s t o n e f a d e s d e p o s i t e d i n e x t r e m e l y s h a l l o w subtidal t o intertidal e n v i r o n m e n t s p a r t i c u l a r l y w e l l k n o w n f r o m t h e M i d d l e O r d o v i c i a n H i g h B r i d g e G r o u p o f K e n t u c k y ( C r e s s m a n a n d N o g e r 1976). T h i s u n i q u e f a c i e s i s a b s e n t f r o m t h e d e e p e r w a t e r f a d e s o f t h e l o w e r and m i d d l e C i n c i n n a t i a n but recurs in the R i e h m o n d i a n Sunset M e m b e r of the Arnh e i m F o r m a t i o n , i n w h i c h four s p e c i e s are f o u n d .

164

A Sea without Fish

Figure 12.1.

One skeletal

element

of a

modern

crinoid,

showing

the

porous

microstructure

(stereom)

typical of all

echinoderms. a

The arm of

crinoid is composed of

a series of these elements,

connected

muscles

and

Comactinia bean.

sp.,

Carib-

Scanning

micrograph,

by

ligaments.

x

electron

79.

Figure 1 2 . 2 . Arm of modern with

crinoid

pinnules

branches) tube

bearing

feet in

ture.

Pinnule

about

1

photo,

(dark) (light fine

feeding poslength

cm. Aquarium comasterid

noid,

Curacao,

lands

Antilles

cri-

Nether-

166

A Sea without Fish

12

ECHINODERMS: A WORLD UNTO THEMSELVES

E c h i n o d e r m s are a m o n g the rarest and m o s t sought-after fossils in t h e C i n -

I .

c i n n a t i a n rocks. N o t o n l y are they c o m p l e x in form a n d s t r u c t u r e , but they

noble

also possess a c e r t a i n b e a u t y a n d mystery that n e v e r fail to attract interest.

as a noble group es-

A n y o n e w h o has visited the seashore is f a m i l i a r w i t h l i v i n g e c h i n o d e r m s s u c h

pecially

designed

puzzle

the

as sea stars or starfish (asteroids), sea u r c h i n s , a n d s a n d d o l l a r s ( b o t h e c h i noids) (Plate 9), O t h e r l i v i n g e c h i n o d e r m s found in d e e p e r m a r i n e waters are

. here salute the echinoderms to

zoologist.

L. H. H y m a n 1955, vi

the sea lilies and feather stars (crinoids), brittle stars (ophiuroids), and sea c u c u m b e r s ( h o l o t h u r o i d s ) (Plate 9). T h e r e are a b o u t 6650 l i v i n g s p e c i e s of e c h i n o d e r m s , a n d over 3500 g e n e r a a n d 13,000 d e s c r i b e d fossil s p e c i e s . The O r d o v i c i a n Period m a r k e d a very significant t i m e in the e v o l u t i o n o f e c h i n o d e r m s , b e c a u s e m a n y different m a j o r g r o u p s ( u s u a l l y r e g a r d e d a s classes) o f e c h i n o d e r m s c o e x i s t e d . L i k e o t h e r i n v e r t e b r a t e p h y l a , t h e oldest fossil e c h i n o d e r m s are found in Early C a m b r i a n r o c k s o v e r 500 m i l l i o n years o l d , but it was not until O r d o v i c i a n t i m e that e c h i n o d e r m s b e g a n to leave a significant fossil r e c o r d . Early in t h e O r d o v i c i a n , e c h i n o d e r m s diversified a l o n g w i t h m a n y o t h e r m a r i n e i n v e r t e b r a t e s , a n d b y L a t e O r d o v i c i a n t i m e a b e w i l d e r i n g variety of e c h i n o d e r m s h a d a p p e a r e d in shallow m a r i n e e n v i r o n m e n t s w o r l d w i d e . A l t h o u g h the f i v e classes o f m o d e r n e c h i n o d e r m s ( c r i n o i d s , asteroids, o p h i u r o i d s , e c h i n o i d s , a n d h o l o t h u r o i d s ) existed t h e n , m a n y o t h e r classes w e r e also p r e s e n t . In s o m e strata of Late Ordovician | M o h a w k i a n ) age, as m a n y as fourteen classes of e c h i n o d e r m s are f o u n d t o g e t h e r ( S p r i n k l e a n d C u e n s b u r g 1997). B e c a u s e s o m e o f t h e s e classes soon b e c a m e e x t i n c t , e c h i n o d e r m d i v e r s i t y h a d d e c l i n e d b y C i n c i n natian t i m e , but still e x c e e d e d p r e s e n t levels, w i t h s e v e n classes f o u n d in the C i n c i n n a t i A r c h r e g i o n . M o r e t h a n o n e o b s e r v e r has n o t e d ( t o n g u e i n c h e e k ) that i f e v e r a n y a n i m a l g r o u p c o u l d h a v e o r i g i n a t e d a s " a l i e n b e i n g s " that l a n d e d o n E a r t h from outer s p a c e , i t w o u l d b e the e c h i n o d e r m s — s o b i z a r r e a r e their b o d y f o r m s , p a r t i c u l a r l y a m o n g t h e w i d e variety w e s e e a m o n g O r d o v i c i a n fossils. T h e features that identify all t h e s e s t r a n g e fossils as e c h i n o d e r m s are not the traits w e u s u a l l y c o n s i d e r c h a r a c t e r i s t i c o f e c h i n o d e r m s , t h e "spiny skin" that gives the g r o u p its n a m e , a n d the f i v e - f o l d ( p e n t a m e r a l ) s y m metry o f the body. T h e s i n g l e m o s t c h a r a c t e r i s t i c trait o f e c h i n o d e r m s i s the n a t u r e of their skeleton. All e c h i n o d e r m s h a v e a m i n e r a l i z e d s k e l e t o n c o m p o s e d o f c a l c i u m c a r b o n a t e a s the m i n e r a l c a l c i t e . U n l i k e o t h e r invertebrates that have calcitic shells, the e c h i n o d e r m skeleton is f o r m e d w i t h i n the m i d d l e cell layer of the body ( m e s o d e r m ) , a n d has a t h i n o u t e r layer of c e l l s c o v e r i n g it ( e c t o d e r m ) , t h u s m a k i n g it an i n t e r n a l s k e l e t o n . B e c a u s e the outer cell layer is so t h i n , we often t h i n k of e c h i n o d e r m s k e l e t o n s s u c h

767

a s sea u r c h i n shells a s e x t e r n a l , b u t i n o t h e r c a s e s , s u c h a s t h e a r m s o f m a n y sea stars, t h e skeletal c o m p o n e n t s , c a l l e d o s s i c l e s , are clearly i n t e r n a l , b e n e a t h a l e a t h e r y " s k i n . " In a d d i t i o n , b e c a u s e it is truly m e s o d e r m a l , the e c h i n o d e r m s k e l e t o n has a u n i q u e m i c r o s t r u c t u r e not f o u n d i n a n y o t h e r a n i m a l g r o u p . T h e c a l c i t e i s f o r m e d a r o u n d m e s o d e r m a l c e l l s into a n intricate t h r e e - d i m e n s i o n a l l a t t i c e w o r k c a l l e d the s t e r e o m ( F i g u r e 12.1). Skele t a l p l a t e s , s p i n e s , o r ossicles t h u s h a v e a h i g h l y p o r o u s s t r u c t u r e i n w h i c h o v e r 50 p e r c e n t of t h e v o l u m e c a n be t a k e n up by p o r e s . In life t h e nurturi n g c e l l s o c c u p y t h e s e p o r e s , b u t after d e a t h , the c e l l u l a r m a t e r i a l d e c a y s , l e a v i n g t h e p o r o u s s k e l e t o n . B u r i e d i n s e d i m e n t , t h e s e p o r e s are u s u a l l y i n f i l l e d w i t h s e c o n d a r y c a l c i t e , a n d the entire skeletal plate displays t h e t y p i c a l r h o m b i c c l e a v a g e o f c a l c i t e . O f t e n t h e m i c r o s t r u c t u r e i s still visible i n t h i n o r p o l i s h e d s e c t i o n s . T h e s e f e a t u r e s h a v e e n a b l e d m a n y fossil e c h i n o d e r m s t o b e c o r r e c t l y i d e n t i f i e d , e v e n t h o u g h their b o d y form m a y b e considerably different from any of the five familiar living groups. Echinoderms are a l s o p e c u l i a r in l a c k i n g s t r u c t u r e s like a d i s t i n c t h e a d , e y e s , or i n t e r n a l s y s t e m s s u c h as a b l o o d c i r c u l a t o r y system or respiratory s y s t e m . I n s t e a d , t h e y are u n i q u e i n h a v i n g a n i n t e r n a l system o f b r a n c h i n g vessels that c o n t a i n n o t b l o o d , b u t a w a t e r y fluid that c i r c u l a t e s d i s s o l v e d o x y g e n a n d d i s s o l v e d w a s t e s a n d p r e s s u r i z e s t h e vessels t h e m selves. T h e vessels t e r m i n a t e i n c h a r a c t e r i s t i c s t r u c t u r e s c a l l e d t u b e f e e t , w h i c h s e r v e i m p o r t a n t f u n c t i o n s for all e c h i n o d e r m s ( F i g u r e 12.2). D i s s o l v e d o x y g e n i s e x c h a n g e d across the t h i n m e m b r a n e o f the t u b e feet a n d d i s s o l v e d w a s t e s are e x p e l l e d . In g r o u p s like c r i n o i d s a n d o p h i u r o i d s , tubefeet are l i k e m i n u t e bristles that c a p t u r e f o o d p a r t i c l e s s u s p e n d e d i n t h e water. S e a stars a n d sea u r c h i n s h a v e t u b e feet w i t h s u c t i o n disks b y w h i c h t h e y c l i n g t o r o c k s , a n d w h i c h aid i n p u l l i n g c l a m s h e l l s apart, i n the c a s e of sea stars, a n d in " w a l k i n g " a c r o s s t h e sea floor. Tube feet are p r a c t i c a l l y n e v e r p r e s e r v e d in fossils, b u t traces of t h e c a n a l s are r e v e a l e d in t h e skele t o n , p r o v i d i n g y e t a n o t h e r i n d i c a t i o n o f e c h i n o d e r m affinity. R e c e n t l y p y r i t i z e d t u b e feet w e r e d i s c o v e r e d i n a C i n c i n n a t i a n o p h i u r o i d , p r o v i d i n g o n e o f t h e f e w c a s e s i n t h e e n t i r e fossil r e c o r d a n d rare e v i d e n c e for pres e r v e d soft tissues a m o n g C i n c i n n a t i a n fossils ( C l a s s 2006). The five-fold or pentameral

body plan seen

in living e c h i n o d e r m s

a p p e a r s i n m a n y o f t h e C i n c i n n a t i a n fossil e c h i n o d e r m s ( F i g u r e s 12.5, 12.10-12.16), b u t this is by no m e a n s a u n i v e r s a l f e a t u r e .

The enigmatic

" c a r p o i d s " l a c k a n y t r a c e o f p e n t a m e r a l form ( F i g u r e 12.17). T h e l a r v a e o f l i v i n g e c h i n o d e r m s are a c t u a l l y b i l a t e r a l l y s y m m e t r i c a l , a n d p e n t a m e r y a p p e a r s o n l y in a d u l t s t a g e s . The five-part s t r u c t u r e is v i r t u a l l y u n i q u e to e c h i n o d e r m s i n t h e A n i m a l K i n g d o m , a n d z o o l o g i s t s h a v e d e b a t e d its sign i f i c a n c e a n d o r i g i n s . S p r i n k l e (1973) f o u n d that p e n t a m e r a l s y m m e t r y f i r s t a p p e a r e d in the food-gathering system of Early and M i d d l e C a m b r i a n e o c r i n o i d s , a n d later d e v e l o p e d i n t h e c a l y x plates a n d respiratory struct u r e s . T h i s s u g g e s t s that p e n t a m e r a l s y m m e t r y p r o v i d e d a n a d v a n t a g e for t h e sessile, f i l t e r - f e e d i n g h a b i t s o f t h e s e early e c h i n o d e r m s . Initially, s o m e e o c r i n o i d s a c t u a l l y h a v e a three-fold radial a r r a n g e m e n t o f t h e f o o d - g a t h e r i n g s t r u c t u r e s that later b e c a m e five-fold b y the b r a n c h i n g o f o n l y two f o o d g r o o v e s o r a m b u l a c r a . B r a n c h i n g b e y o n d the f i v e - f o l d pattern m a y

168

A Sea without Fish

h a v e b e e n l i m i t e d b y the a v a i l a b l e s p a c e a r o u n d t h e m o u t h , a n d t h u s t h e p e n t a m e r a l pattern m a y h a v e b e e n the most efficient s o l u t i o n . O n c e p e n t a m e r a l s t r u c t u r e b e c a m e g e n e t i c a l l y p r o g r a m m e d in Echinoderms, it persisted e v e n i n g r o u p s that g a v e u p t h e a n c e s t r a l m o d e o f life t o b e c o m e m o b i l e sea stars or sea u r c h i n s . D e s p i t e their m a n y " a l i e n " features, E c h i n o d e r m s a r e s i g n i f i c a n t a s o n e of the invertebrate phyla m o s t closely related to o u r o w n , the c h o r d a t e s . For a l o n g t i m e zoologists s t u d y i n g the e m b r y o n i c d e v e l o p m e n t of echinoderms have r e c o g n i z e d close similarities in the early d e v e l o p m e n t of echinoderms and chordates. B o t h g r o u p s have s y m m e t r i c a l cell division in the fertilized e g g , i n d e t e r m i n a t e d e v e l o p m e n t ( e m b r y o n i c cells are not p r e p r o g r a m m e d to form a specific adult tissue), a n d the internal b o d y cavity, t h e c o e l o m , forms in the s a m e way in the e m b r y o . R e c e n t studies of m o l e c u l a r c o m p o s i tion o f a n i m a l phyla d e m o n s t r a t e that e c h i n o d e r m s are m u c h m o r e closely allied to h e m i c h o r d a t e s and c h o r d a t e s than to any o t h e r g r o u p (Raff C o m p l e t e fossil

echinoderms

are

1996).

i n d e e d rare fossils in C i n c i n n a t i a n

strata, but the a b u n d a n c e of their isolated skeletal c o m p o n e n t s suggests that t h e y w e r e very c o m m o n m e m b e r s o f sea floor c o m m u n i t i e s d u r i n g the O r d o v i c i a n . The reason for their rarity as c o m p l e t e fossils is f o u n d in the n a t u r e of the e c h i n o d e r m skeleton, c o m p o s e d of m y r i a d tiny plates or ossicles, all held together in life by fibers of c o n n e c t i v e tissue that p e n e t r a t e pores of the s t e r e o m i c skeleton. U p o n d e a t h , these f i b e r s rapidly d e c a y ; the skeletal c o m p o n e n t s separate, a n d are u s u a l l y dispersed b y w a t e r m o v e m e n t ( F i g u r e 12.3A). A m o n g t h e m o s t c o m m o n fossils f o u n d a r o u n d C i n c i n n a t i are t h e disk-like or ring-like s e g m e n t s of the c r i n o i d stem ( c o l u m n a l s ; F i g u r e s 12.3A, 12.5). T h e s e are often isolated like

tiny

LifeSavers

or still c o n n e c t e d in vary-

ing l e n g t h s like strings of b e a d s . Entire l i m e s t o n e layers often consist of n o t h i n g but dissociated crinoid c o l u m n a l s , o r i g i n a l l y c r i n o i d a l sands, s o m e times sorted b y c u r r e n t s into z o n e s o f c o m m o n size, a n d f o r m e d into rippled surfaces. B e c a u s e echinoderms are so s u s c e p t i b l e to b r e a k u p of t h e skeleton after d e a t h , the o c c u r r e n c e of c o m p l e t e , a r t i c u l a t e d skeletons u s u a l l y requires rapid burial in s e d i m e n t .

Thus, c o m p l e t e c r i n o i d s are f o u n d w i t h i n

shales or on the u p p e r s u r f a c e of l i m e s t o n e s c o v e r e d by shales, or m o r e rarely at the base of c a l c a r e o u s siltstones. T h e very n a t u r e of this c o m p l e t e preservation provides a v a l u a b l e c l u e that the e n c l o s i n g s e d i m e n t w a s in fact d e p o s ited rapidly, probably t i m i n g storms, either as stirred up b o t t o m s e d i m e n t s or underwater mudslides.

T h e seven classes o f e c h i n o d e r m s f o u n d i n C i n c i n n a t i a n strata are t h e

Echinoderms of

Crinoidea, Rhomhifera, Kdrioasteroidca, Asteroidea, Ophiuroidea, C y c l o -

t h e Cincinnatian

c y s t o i d e a , a n d S t y l o p h o r a . o f t h e s e , the c r i n o i d s a r e t h e m o s t a b u n d a n t i n the f i e l d a n d the m o s t d i v e r s e i n n u m b e r o f s p e c i e s .

Crinoids S t e m m e d crinoids (sea lilies) are a t t a c h e d to the sea floor by m e a n s of a holdfast or root, and elevated a b o v e the b o t t o m by a stem c o m p o s e d of m a n y c o -

Echinoderms

169

Figure 12.3.

Variable

preservation

of

locrinus

crinoids.

subcrassus

(Meek

and

Worthen).

A. Articulated

individual

with

partially disarticu-

lated

sections

and matrix lated

of stalk,

of disarticu-

skeletal

nents.

compo-

Upper

Ordovician,

Corryville Formation, cinnati, of

Cin-

Ohio.

University

Cincinnati

collections.

B. Two

articulated

crowns,

detached

stalk, but in

opposite

preserved on bed.

from

oriented parallel direction,

base

of

Upper Ordovician,

Corryville

Formation,

Clermont Co.,

Ohio.

CMC

IP 44362. Scale in mm. B in

upper right denotes

basal plate; radial

R denotes

plate.

l u m n a l s ( F i g u r e s 12.3-12.5). T h e b o d y is e n c l o s e d w i t h i n a plated c a l y x c o m p o s e d of t h e l o w e r c u p a n d a roof-like

tegmen.

T h e c u p has a regular

a r r a n g e m e n t of plates: a circlet of five radials, a n d either o n e circlet ( m o n o There were also s o m e beautiful noidea,

forms

cyclic) of basals or t w o circlets (dicyclic) of basals a n d infrabasals o c c u r r i n g

of Cri-

or stone-lilies .

.

C h a r l e s Lyell 1845, 50

a b o v e t h e stem ( F i g u r e s 12.3B, 12.10A). T h e a r m s arise from the radials of the c u p a n d usually b r a n c h a n d m a y support finer b r a n c h e s , the p i n n u l e s , g i v i n g the a r m a feathery a p p e a r a n c e ( F i g u r e 12.4). T h e a r m s and p i n n u l e s carry the food g r o o v e s (ambulacra) w h i c h c o n v e y tiny food particles to the m o u t h situated on the u p p e r surface of t h e c a l y x . I .iving crinoids are passive suspension feeders, d e p e n d e n t on currents to supply food particles to the a w a i t i n g feedi n g apparatus. H i e a n i m a l c o n s t r u c t s a filtration fan of the ar m s and pinnules

770

A Sea without Fish

Figure tion

12.4. of

Reconstruc-

Glyptocrinus

decadactylus

in

life

po-

sition. Calyx is in a horizontal position,

with

the

arms splayed into a filtration fan.

By analogy with

living crinoids,

current

flow was from left to right. Agnew.

Echinoderms

171

Drawing by John

Figure 12.5. Cincinnatian crinoid columnals and holdfasts. A,

H.

naticrinus

Cincin-

varibrachialus

Warn and Strimple;

A.

Articular surface x 9.6; H. Lateral view of mature section x 5.9. B, enocrinus

I. Ect-

simplex

(Hall).

B. Articular surface

y.9.6;

I.

Lateral view*

12.6. C,

J.

locrinus sub-

crassus (Meek and Worthen).

C. Articular

surface x 5.2;

J. iafera/

view x 4.4. D, G, Glyptocrinus lus Hall; D, surfaces

K. decadacty-

G. Articular

of internodal,

nodal respectively, 4.4;

x

K. Lateral view x 6;

note three cycles ofinternodals.

E.

Merocrinus

curtus Ulrich, articular surface x 5.2. alocrinus

F.

Anom-

incurvus

(Meek

and Worthen), lateral view of

compressed

with

section

fracture separating

meres, x 1. A - K , from Meyer et al. (2002, figure 2) and reprinted by permission of The Paleontological Society. nus

I,

M. Lichenocri-

crateriformis

Hall,

Two speci-

arrayed p e r p e n d i c u l a r to c u r r e n t Flow, thus a c t i n g as a " f l o w - t h r o u g h " filter

mens attached to brachio-

(Plates 9A, B). T i n y t u b e feet l i n i n g the p i n n u l a r food grooves snare food

FMNH8810. L.

pod, x 1.6. M. Enlarge-

particles s u c h as o r g a n i c detritus a n d p l a n k t o n and stuff t h e m into the food

ment of larger specimen in

g r o o v e for transport to the m o u t h . The close similarity of O r d o v i c i a n crinoids

I, y.3.7, Waynesville For-

to m o d e r n forms suggests that a n c i e n t crinoids used similar f e e d i n g postures

mation, Warren Co., Ohio. From Faber (1929, plate 32, figures 5, 6) and reprinted by permission of the American uralist.

Midland N.

milleri Faber,

Nat-

Lichenocrinus

a n d m o d e s o f c a p t u r i n g food, and w e c a n i m a g i n e that they looked quite like s t e m m e d c r i n o i d s that today exist o n l y in the d e e p sea (Plate qA). C r i n o i d c o l u m n a l s a r e a m o n g t h e m o s t c o m m o n l y e n c o u n t e r e d fossils i n t h e C i n c i n n a t i a n . T h e y are Found e i t h e r a s s i n g l e c o l u m n a l s o r a r t i c u lated s e c t i o n s o F t h e s t e m ( f i g u r e s 12.3, 12.5). A l t h o u g h s u p e r f i c i a l l y very s i m i l a r i n a p p e a r a n c e , c o l u m n a l s c a n u s u a l l y b e identified t o g e n u s . C r i -

CMC IP

10047, Elkhorn Formation,

n o i d s p e c i e s are u s u a l l y d e s c r i b e d from s p e c i m e n s o f the c a l y x o r c r o w n

cross-section

that are less c o m m o n .

showing

floor

plate with central node,

T w e n t y - o n e g e n e r a o f c r i n o i d s a r e k n o w n From the C i n c i n n a t i region.

crater plates, and base of column, y.3.7, from Faber (1929, plate 33, figure 9).

172

S o m e g e n e r a are m o n o s p e c i f i c ( h a v i n g o n l y o n e species) and others have m o r e t h a n o n e s p e c i e s , b r i n g i n g to t w e n t y - e i g h t the total n u m b e r oF species in the local area. C i n c i n n a t i a n c r i n o i d s represent all three oF the subclasses A Sea without Fish

Figure A,

12.6. B.

(Ulrich),

Cincinnatian disparid crinoids.

YPM 24801,

Fairview Formation,

showing regeneration of arms, crinus geniculatus (Ulrich), E. simplex (Hall) plate 3, the

A,

Holotype, CMC IP 3871, Kope Formation,

figures

F. CMC IP, x 7.5. 1, 2, plate 6,

Paleontological

Research

Cincinnati,

USNM 93223,

CMC IP 36313, figure

B.

Ohio,

Ohio, x

Fairview Formation,

Kope Formation, G.

Cincinnaticrinus varibrachialus

Cincinnati,

x

1.3.

1.0 and x 3.1. D. Ohio,

C. pentagonus

C.

Dystactocrinus constrictus (Hall),

Hamilton Co.,

Cincinnati,

Warn andStrimple.

x

Ohio, 7.4.

x 2.0. F,

E.

Ecteno-

G.

CMC IP 42679, x 0.3. A - C , E, G from Warn and Strimple (1977,

1, plate 13,

figure 3, plate!4,

figure 8) and reprinted by permission of

Institution.

Echinoderms

173

Figure

12.7.

Cincinnatian disparid crinoids.

horizon and locality unknown, Formation,

Cold Spring,

logued, Cincinnati, OH,

x

1.4.

Kentucky, x

174

1.4.

x D.

B-D. 1.8.

A.

locrinus subcrassus (Meek and Worthen),

Anomalocrinus. C.

B.

A. sp,

Arms of A. incurvus Meek and Worthen,

A. sp, CMC IP 7341, Cincinnati, Ohio.

A Sea without Fish

CMC IP 170,

MUGM 28048,

Bellevue-Corryville CMC IP,

uncata-

Figure 12.8. monobathrid

camerate

crinoids. nus

Cincinnatian

A.

Glyptocri-

decadactylus

MUGM

28046,

Formation

(?),

locality

unknown, x 1.5. Pycnocrinus (Meek), Corryville Morrow,

175

B.

dyeri

USNM 40762, Formation, Warren

Ohio, x 1.2.

Echinoderms

Hall, Fairview

Co.,

Figure 28121,

12.9.

Cincinnatian

Liberty Formation,

Cyclonema sp.,

monobathrid camerate crinoids. Butler Co.,

MUGM uncatalogued,

Wayne State University Collection, eter.

Note

Figure tion,

12.10.

Formation, S9I,

A.

A.

B.

Arnheim Formation,

Dent,

Dent,

of articulated crowns,

x

7.2.

C.

east of Lebanon,

Warren Co.,

A Sea without Fish

Ohio, Ohio,

No. 366,

MUGM

Ohio,

x

1.3.

x 2.0.

C.

P.

dyeri,

lens cap 55 mm diamdown.

Bruce and Charlotte Gibson Collec-

Xenocrinus baeri (Meek),

Diplobathrid camerate crinoid,

figure 3a).

176

Co.,

some splayed oralside

Merocrinus curtus Ulrich, B.

Hamilton Co.,

Hamilton

Ohio,

x 4.2.

Glyptocrinus fornshelli Miller,

Pycnocrinus dyeri (Meek) with attached gastropod,

Cladid crinoid,

southwestern Ohio, plate 2,

7.7.

Hamilton Co.,

Waynesville Formation,

Meek (1873,

x

Arnheim Formation,

remarkable preservation

Kope Formation,

Ohio,

MUGM 28347,

Liberty

Gaurocrinus nealli (Hall) USNM

This specimen was illustrated by

Echinoderms

177

Figure 12.11. Cincinnatian

of c r i n o i d s , the disparids, the c l a d i d s , a n d tlic c a m c r a t c s . Disparids have a

rhombiferans.

s m a l l , m o n o c y c l i c c u p - o r h o w l - s h a p e d c a l y x w i t h b r a n c h i n g a r m s that d o

A, B.

padocystis

Le-

moorei

(Meek),

CMC IP 24680,

Elkhorn

Formation,

ble Co.,

Ohio,

C.

fulton-

Sumrall and Schu-

macher,

holotype,

IP 50402, tion,

x 4.3.

Cheirocystis

ensis

Pre-

CMC

n o t b e a r p i n n u l e s . An e l o n g a t e , plated t u b e , the a n a l sac. is often present b e t w e e n the a r m s a n d has the a n a l o p e n i n g a t its e n d . T h e m o s t c o m m o n Cincinnatian

c r i n o i d s , Cincinnaticrinus,

Ectenocrimts,

and

locrinus are dis-

parids ( F i g u r e s 12.6,12.7; Plate 10). Cincinnaticrinus a n d probably Ectenocrimis h a d a u n i q u e , button-like holdfast c o m p o s e d of m a i n tiny plates, often f o u n d a t t a c h e d to b r a c h i o p o d shells a n d o t h e r hard substrata. Before it was

Kope Forma-

r e c o g n i z e d that this holdfast b e l o n g s to these types of crinoids, if was given

Bracken Co., Ken-

t h e n a m e Lichenocrinus w i t h n u m e r o u s s p e c i e s ( F i g u r e s 1 2 . 5 L - N ; Faber

tucky, x 3.5. struction

D.

Recon-

of late

Riehmondian

sea

southeastern

Indiana

southwestern showing moorei

(A)

attached

(B),

to

brachiomod-

and an edrioast-

Carneyella sp.

(D).

A, B, D from Kesling and Mintz (1961, plate 6, ures 8, reprinted

of the Museum ontology,

fig-

10, plate 7) and by

served fossils are f o u n d that reveal the entire a n i m a l . Cincinnaticrinus

Ohio,

Zygospira

esta (C), eroid,

and

Lepadocystis

bryozoans pods,

floor of

1929; W a r n a n d S t r i m p l e 1977). Q u i t e often in p a l e o n t o l o g y isolated parts of o n e o r g a n i s m are d e s c r i b e d as distinct s p e c i e s before sufficiently well preand

Ectenocrinus

are

frequently

found

together

in

t h e K o p e F o r m a t i o n , w h e r e their d i s a r t i c u l a t e d c o l u n m a l s c a n form entire l i m e s t o n e b e d s . S o m e t i m e s t h e a r t i c u l a t e d stalks a r e p a c k e d tightlv tog e t h e r like l o g j a m s w h e r e t h e c o l l e c t o r s h o u l d l o o k c l o s e l y for t h e s m a l l , d e l i c a t e c r o w n s ( Plate 10B). T h e s e " l o g j a m s " w e r e p r o b a h l v f o r m e d d u r i n g a n c i e n t s t o r m s that d i s r u p t e d t h e sea floor. locrinus is a n o t h e r c o m m o n disparid c r i n o i d in t h e C i n c i n n a t i a n , but is larger a n d m o r e robust in s t r u c t u r e than (lincinnaticrinus and Ectenocrinus ( F i g u r e 12.7A; Plate 10A). locrinus has a low, c o n i c a l c u p with dec]) in-

permission

d e n t a t i o n s m a r k i n g the j u n c t i o n of e a c h basal plate with the two radials

of Pale-

a b o v e . T h e c o l u n m a l s are p e n t a g o n a l or star-shaped ( F i g u r e s 12.5C, J). A d u l t

University of

locrinus a t t a c h e d to b r y o z o a n s by c o i l i n g t h e stalk tightly a r o u n d the

Michigan.

b r a n c h e s . Slabs c o v e r e d w i t h locrinus c r o w n s h a v e b e e n f o u n d in the u p p e r C o r r y v i l l e F o r m a t i o n . In o n e e a s e , t h e c r o w n s are c o n c e n t r a t e d at the base of t h e fine-grained l i m e s t o n e b e d a n d are a l i g n e d parallel to a narrow gutter e r o d e d into the sea floor ( F i g u r e s 12.^B; M e y e r el al. 19(81). C u r v e d l e n g t h s of the locrinus stalks c o v e r the u p p e r surface of the bed in a r a n d o m fashion. These preservational features s u g g e s t that the c r o w n s were s n a p p e d off the stalks by a violent d i s t u r b a n c e (possibly storm-related) and swept d o w n s l o p e , to he f o l l o w e d by their stalks that settled on top of t h e m . Anomalocrinus w a s t h e g i a n t a m o n g t h e c r i n o i d s o f t h e C i n c i n n a t i a n ( F i g u r e s 1 2 . 7 B - D ) . Its s t e m r e a c h e d a l e n g t h o f a b o u t o n e m e t e r , with c o l u n m a l s o v e r a c e n t i m e t e r in d i a m e t e r ( F i g u r e 12.5F). least 10 cm h i g h a n d had up to 500 b r a n c h e s .

The c r o w n was at

The s t e m w a s a t t a c h e d by

m e a n s o f a s t u m p - l i k e holdfast c e m e n t e d d i r e c t l y t o hard substrata. T h e holdfasts are f o u n d a s w o r n , crater-like l u m p s e n c r u s t i n g l i m e s t o n e n o d u l e s , h a r d g r o u n d s , b r y o z o a n s , o r shells. C l a d i d s h a v e a c o n i c a l , d i e v c l i c c u p . Mcrocrinus is restricted to t h e l o w e r m o s t K o p e F o r m a t i o n w h e r e its s t e m s are easily r e c o g n i z e d b y their t h i n , wafer-like c o l u n m a l s ( F i g u r e s 12.5E,

12.10A).

Cupulocrinusand Plico-

dendrocrinus are c l a d i d s f o u n d in t h e R i e h m o n d i a n f o r m a t i o n s (Plate 11). C a m e r a t e c r i n o i d s h a v e a rigid c o n i c a l calyx that i n c l u d e s m a i n ' fixed b r a c h i a l s , that is, a r m plates a b o v e the radials that are incorporated into the c a l y x . T h e r e is a plated t c g i n e n c o v e r i n g the m o u t h .

The p i n n u l e - b e a r i n g

free a r m s h a v e a feathery a p p e a r a n c e . ('dyptocrinus and Pycnocrinus, 1110110-

178

A Sea without Fish

Echinoderms

179

Figure 12.12. Edrioasteroid

Isorophus

tiensis

cincinna-

(Roemer),

recon-

structed as in life, food grooves feeding.

with

open

for

Drawing by John

Agnew.

Figure

12.13. Cincinnatian

edrioasteroids

A,

B.

cincinna-

Isorophus

tiensis A.

(Roemer).

Corryville Formation,

Hamilton Co., versity

Ohio,

lection, x 2.2. individual against

B.

smaller

individual,

of

Carneyella

C-E.

E. At-

crinoid column,

CMC IP 26324, F.

Streptaster

vorticel-

CMC IP

24700, x3.2.

G.

stellatus

CMC IP 40481, Photos C - G

(Hall),

13,

10,

figure

figure14, plate

figure 7) and re-

printed by permission Albany,

very d i s t i n c t f r o m G. decadactylus in h a v i n g finer ridges on the calyx plates a n d u n i q u e t h i n , p e n t a g o n a l c o l u m n a l s ( F i g u r e 12.9A). Xenocrinus is a n o t h e r m o n o b a t h r i d c a m e r a t e crinoid f o u n d in the L i b erty F o r m a t i o n of t h e R i c h m o n d i a n S t a g e ( F i g u r e 12.10B). T h i s crinoid is

of

the New York State Museum,

of Glyptocrinus, p r e s e r v e d c o m p l e t e w i t h a r m s , p i n n u l e s , and attached stalks preparation at t h e C i n c i n n a t i M u s e u m C e n t e r ) . Glyptocrinus fornshelli is

10, plate 17, figures 1, 3, plate

type was found in the A r n h e i m Formation at D e n t , Hamilton C o u n t y ,

w a s r e c o v e r e d f r o m t h e F a i r v i e w F o r m a t i o n n e a r M a y s v i l l e , K e n t u c k y (in

x 6.2. 16,

( F i g u r e 12.4). O c c a s i o n a l l y , m u d s stirred u p d u r i n g storms s m o t h e r e d dense

a r o u n d i 9 6 0 ( F i g u r e 1 2 . 9 C ) , a n d recently a d e n s e a g g r e g a t i o n of h u n d r e d s Cys-

from Bell

(1976a, plate

nocrinus c o i l e d t h e s t e m a r o u n d o b j e c t s s u c h as b r y o z o a n s for a t t a c h m e n t a g g r e g a t i o n s of these c r i n o i d s . A s p e c t a c u l a r Pycnocrinus a g g r e g a t i o n of this

x 2.1.

latus (Hall), taster

n e a r t h e base, p r o d u c i n g a total of t w e n t y a r m s . B o t h Glyptocrinus and Pyc-

C. CMC IP to

a r m s . Pycnocrinus o c c u r s in t h e C o r r y v i l l e , A r n h e i m , and W a y n e s v i l l e Form a t i o n s a n d has several s e e u n d i b r a c h s and ten free a r m s that b r a n c h o n c e

pilea

34537, x 3.2. D, tached

braehs (calyx plates f o l l o w i n g the first b r a n c h i n g of a rav) and twenty free

Cincinnati

collection, x 3.

pattern of ridges on t h e c a l y x plates. Glyptocrinus decadactylus o c c u r s in the l o w e r C i n c i n n a t i a n K o p e a n d F a i r v i e w F o r m a t i o n s and has t w o s e c u n d i -

Kentucky,

University

bathrid c a m e r a t e s ( m o n o c y c l i c calyx), are very similar a n d are the m o s t c o m m o n C i n c i n n a t i a n c a m e r a t e s ( F i g u r e 12.8). B o t h h a v e a distinct g e o d e s i c

Formation,

Co.,

(Hall).

Large

crowding

Corryville Boone

Uni-

of Cincinnati col-

N.Y.,

n o t e w o r t h y for h a v i n g four-sided c o l u m n a l s and also h a v i n g the ability to coil a r o u n d o t h e r objects ( D o n o v a n et al. 1995). D i p l o b a t h r i d camerates have an additional circlet of plates, the infrabasals, at the base of the calyx and are quite

12230.

rare in the C i n c i n n a t i a n . Gaurocrinus nealli is s h o w n in F i g u r e 12.10C.

180

A Sea without Fish

Echinoderms

181

Figure

12.14. Cincinnatian

asteroids. A,

B.

mopalaeaster

Prospecio-

sus (Meek).

A.

Associations of Crinoids with O t h e r Species Interesting i n f o r m a t i o n a b o u t the e c o l o g y o f C i n c i n n a t i a n crinoids c a n b e g a i n e d b y o b s e r v i n g c l o s e associations b e t w e e n crinoids a n d other o r g a n -

Oral

Aboral side,

isms. A s m e n t i o n e d a b o v e , s o m e C i n c i n n a t i a n crinoids used other o r g a n i s m s

holotype,

Maysvillian,

o n t h e sea f l o o r , u s u a l l y b r y o z o a n s , for a t t a c h m e n t . T h i s habit a l l o w e d the

Cincinnati,

Ohio,

c r i n o i d s to g a i n e l e v a t i o n a b o v e t h e sea floor that e x p o s e d t h e m to u n r e -

side.

B.

108059, x 2. mopalaeaster e s (Miller) side. holotype,

magnifiC.

D.

MCI

C, D. ProOral

Richmondian,

40883,

Waynes-

ville, Warren Co., Ohio, x 0.8.

o f a v o i d i n g c o m p e t i t o r s . C r i n o i d s w e r e thus m e m b e r s o f s o m e o f the earliestk n o w n " t i e r e d " m a r i n e b o t t o m c o m m u n i t i e s , i n w h i c h p a r t i c u l a r species,

Aboral side, USNM

stricted c u r r e n t flow, an a d v a n t a g e in passive suspension f e e d i n g a n d a m e a n s

Photos courtesy of

Jon W. Branstrator.

e s p e c i a l l y s u s p e n s i o n feeders, o c c u p y preferred levels or tiers a b o v e the subs t r a t u m . C r i n o i d s h a v e b e e n " u p p e r story" o c c u p a n t s o f tiered c o m m u n i t i e s from O r d o v i c i a n t i m e up t h r o u g h the present (Ausich and Bottjer 1982). Man\- C i n c i n n a t i a n s p e c i e s i n t u r n u s e d c r i n o i d s a s a t t a c h m e n t sites. C r i n o i d s t e m s are f r e q u e n t l y e n c r u s t e d w i t h b r v o z o a n s , c o r a l s , c o r n u l i t i d w o r m t u b e s , b r a c h i o p o d s , e d r i o a s t e r o i d e c h i n o d e r m s ( F i g u r e s 12.13D, F ) , a n d e v e n o t h e r c r i n o i d holdfasts. B e c a u s e t h e s e e n c r u s t e r s often e n c i r c l e t h e stalk, it is likelv s o m e w e r e a t t a c h e d d u r i n g t h e life of t h e c r i n o i d , p r o v i d i n g t h e e n c r u s t e r s t h e a d v a n t a g e o f a h i g h e r t i e r i n g level. Pits, b o r i n g s , a n d gall-like s w e l l i n g s in c r i n o i d stems indicate that other o r g a n i s m s u s e d t h e s t e m s as d w e l l i n g sites or e v e n parasitized t h e crinoid host. S t e m s of Cincinnaticrinus s o m e t i m e s h a v e gall-like s w e l l i n g s p e n e trated by a pit. C a l c i u m p h o s p h a t i c rings found either w i t h i n the pit or on the surfaces o f u n p i t t e d c o l u m n a l s ( W a r n 1974)

w

c

r

c

probably f o r m e d b y the

o r g a n i s m m a k i n g t h e pits, a l t h o u g h its identification is disputed. W a r n (1974) c o n c l u d e d that t h e O r d o v i c i a n d e f o r m i t i e s a n d rings w e r e c a u s e d b y m y z o s t o m i d a n n e l i d w o r m s that also form galls in living crinoids. W e l c h (1976) p o i n t e d o u t that n o m o d e r n m y z o s t o m i d s form p h o s p h a t i c l i n i n g s w i t h i n their pits. H e r e c o g n i z e d that t h e O r d o v i c i a n s t r u c t u r e s r e s e m b l e others f o u n d i n y o u n g e r P a l e o z o i c c r i n o i d s t e m s a n d thus c o u l d b e assigned t o the g e n u s Phosphannulus.

B i s c h o f f (1989) c o n s i d e r e d Phosphannulus to be a

junior s y n o n y m of Byronia, w h i c h b e l o n g s to a g r o u p of p h o s p h a t i c and/or o r g a n i c t u b e - s h a p e d fossils (byroniids) f o u n d i n C a m b r i a n t h r o u g h P e r m i a n strata. A l t h o u g h s o m e w o r k e r s interpret b y r o n i i d s as t u b e s of tiny s u s p e n s i o n f e e d i n g w o r m s , B i s c h o f f a r g u e d that the}' are s h e a t h s of the p o l y p o i d larval stage o f s c y p h o z o a n jellyfish. ( W e discussed the association b e t w e e n crinoids a n d g a s t r o p o d s [ F i g u r e 12.9I in c h a p t e r 9.) T h a n k s to m o d e r n o c e a n o g r a p h y , m a r i n e biologists c a n e x a m i n e m a n y l i v i n g d e e p sea a n i m a l s s u c h a s stalked c r i n o i d s that w e r e p r e v i o u s l y i n a c c e s s i b l e e x c e p t b y d r e d g i n g . O n e o f t h e m o s t s u r p r i s i n g r e c e n t discoveries a b o u t l i v i n g c r i n o i d s w a s o c c a s i o n a l c o l u m n s l a c k i n g c r o w n s s t a n d i n g in t h e m i d s t of d e e p sea c r i n o i d " g a r d e n s " ( C o n a n et al. 1981). A f u r t h e r s u r p r i s e c a m e w h e n J a p a n e s e w o r k e r s d i s c o v e r e d that " h e a d l e s s " c o l u m n s o f R e c e n t Metacrinus c a n live i n d e f i n i t e l y i n a q u a r i a a n d e v e n r e g e n e r a t e t h e c r o w n i f r e g e n e r a t i o n o c c u r s a b o v e t h e basal circlet o f plates ( A m e m i y a a n d O j i 1992). T h i s s u r v i v a l a n d r e g e n e r a t i o n i s p r e s u m a b l y e n a b l e d b y d i r e c t a b s o r p t i o n o f d i s s o l v e d n u t r i e n t s . F o s s o f the c r o w n s a m o n g wild p o p u l a t i o n s of c r i n o i d s is m o s t likelv the result of p r e d a t i o n .

\82

A Sea without Fish

C i n c i n n a t i a n fossil c r i n o i d s p r o v i d e s o m e o f t h e earliest e v i d e n c e t h a t predators inflicted s i m i l a r d a m a g e o n O r d o v i c i a n c r i n o i d s a n d t h a t r e g e n eration w a s a survival m e c h a n i s m . In a s t u d y of t h e i m p a c t of p r e d a t i o n on P a l e o z o i c c r i n o i d s , B a u m i l l e r a n d C a l m (2004) illustrated a r e m a r k a b l e s p e c i m e n of the disparid Dystactocrinus comtrictus ( H a l l ) f r o m t h e C i n -

Echinoderms

183

Figure

12.15.

side.

B.

Cincinnatian asteroids.

Oral side,

(Miller and Dyer),

holotype,

(Meek),

MUGM 29664,

mation,

Brookville,

Waynesville,

A,

B.

Lanthanaster intermedius (Schuchert).

holotype, FMNH 9575, Maysvillian, MCZ 108063,

with arms

Franklin

Warrern Co.,

184

Co.,

Ohio,

Maysvillian,

Cincinnati,

Preble Co.,

wrapped around bivalve

Indiana.

E.

x 3. Photos A,

A Sea without Fish

Ohio, Ohio,

A.

Aboral

x 3.

C.

Petraster speciosus

7.

D.

Promopalaeaster dyeri

x

in presumed feeding posture,

Salteraster grandis (Meek),

USNM 40885,

B courtesy of Jon W. Branstrator.

Waynesville ForRichmondian,

Figure

12.16.

Waynesville,

A.

Asteroid,

Warren Co.,

Ohio,

cian, southern Pennsylvania, Boardman

et

Publishing;

C,

al.

(1987,

x

figure

Hudsonaster simplex (Miller and Dyer), x 3.1. 1.4.

B. C.

18.45B),

USNM 40882,

Taeniaster spinosus (Billings),

Cyclocystoid,

USNM,

Richmondian,

Zygocycloides magnus (Miller and Dyer).

courtesy of James Sprinkle,

near

Middle or Upper OrdoviB,

from

and reprinted by permission of Blackwell

courtesy of Colin Sumrall. Echinoderms

185

Figure

12.17.

stylophoran A.

1-6.

1 -3.

sal view.

3.

view, x 2.3. type,

2.

CMC IP 25257,

ryville Formation, ton Co., Ohio. view. 6. 1-6

5.

Dor-

c o l u m n a l s ) o f Cincinnaticrinus s h o w i n g r o u n d e d o v e r g r o w t h s o f o n e e n d . T h e y s u g g e s t e d t h a t t h e o v e r g r o w t h s f o r m e d after d e c a p i t a t i o n o f t h e

Lateral 4-6.

r e p o r t e d r e g e n e r a t i o n of a c o l u m n a t t a c h e d to t h e holdfast Lichenocrinus D o n o v a n a n d S c h m i d t (2001) illustrated p l u r i c o l u m n a l s (sections o f several

Ohio.

Ventral view.

a r m s t o a n a t t a c k b y a n u n k n o w n predator. A u s i c h a n d B a u m i l l e r (1993) dubius ( k n o w n to be t h e h o l d f a s t of Cincinnaticrinus or o t h e r disparids).

Formation,

Clermont Co., 1.

Holo-

CMC IP 25993,

Corryville

c i n n a t i a n i n w h i c h all o f t h e a r m s a r e i n t h e p r o c e s s o f r e g e n e r a t i o n ( F i g u r e 12.6D). T h e y c o n c l u d e d that t h e r e g e n e r a t i o n f o l l o w e d t h e loss o f t h e

Enoploura p o -

p e / Caster. type,

Cincinnatian carpoids.

Para-

c r o w n s b y p r e d a t i o n , l e a v i n g a " h e a d l e s s " c o l u m n . I n light o f t h e n e w

Cor-

k n o w l e d g e of p r e d a t i o n d a m a g e in l i v i n g c r i n o i d s , it is m o s t likely that

Hamil4. Dorsal

Lateral view.

p r e d a t o r s a l s o c a u s e d loss o f c r o w n s a n d a r m s i n O r d o v i c i a n c r i n o i d s , alt h o u g h the identity of the culprits remains uncertain.

Ventral view, x 2.3. from

plate 1).

Caster (1952, B.

tion of E. popei, Parsley

Rhombiferan "cystoids"

Reconstruc-

(1991,

R h o m b i f e r a n s are stalked e c h i n o d e r m s that a p p e a r e d i n the Early O r d o v i -

from

text-figure

cian and b e c a m e extinct by the Late D e v o n i a n .

T h e term " c y s t o i d " (sac-

1). All reprinted by per-

like) refers to t h e plated t h e c a that has four to five circlets of large plates

mission

of the

a r r a n g e d in a p e n t a m e r a l p a t t e r n . R h o m b i f e r a n s w e r e o r i g i n a l l y a s u b -

logical

Research

Paleonto-

g r o u p o f t h e cystoids b u t h a v e b e e n e l e v a t e d t o a separate class. T h e y lived

Institution.

as suspension feeders, but unlike crinoids, the feeding appendages of r h o m b i f e r a n s are t h i n p l a t e d b r a c h i o l c s a r i s i n g f r o m a m b u l a c r a that are e i t h e r i n c o r p o r a t e d into t h e t h e c a o r less c o m m o n l y stand e r e c t ( F i g u r e 12.11C). R h o m b i f e r a n s are n a m e d for a u n i q u e r h o m b i c s t r u c t u r e f o u n d on t h e t h e c a l plates. A set of n a r r o w slits in a r h o m b i c o u t l i n e crosses b o u n d a r i e s o f a d j a c e n t p l a t e s ; t h e s e slits led t o i n t e r c o n n e c t i n g i n t e r n a l c a n a l s . T h e p u r p o s e o f t h e s e d i s t i n c t i v e c a n a l s w a s t o p r o v i d e w a t e r flow t h r o u g h t h e interior o f t h e t h e c a for respiratory p u r p o s e s . T h e relatively short b r a c h i o l e s o f r h o m b i f e r a n s m a y h a v e c a r r i e d f e w e r t u b e feet t h a n t h o s e u s e d for r e s p i r a t i o n i n c r i n o i d s , o r m a y h a v e l a c k e d t h e m entirely. T h e r e f o r e t h e h e a v i l y p l a t e d r h o m b i f e r a n s m a y h a v e n e e d e d a different m e a n s t o s u p p l y o x y g e n a t e d w a t e r a n d t o r e m o v e dissolved c a r b o n d i o x i d e f r o m t h e t h e c a l interior. T w o s p e c i e s o f r h o m b i f e r a n s are f o u n d i n t h e C i n c i n n a t i a n . Cheirocystis fultonensis is restricted to t h e l o w e r m o s t K o p e

Formation (Fulton

S h a l e ) ( S u m r a l l a n d S c h u m a c h e r 2002). T h i s s p e c i e s has a n e l o n g a t e t h e c a a n d a l o n g , t a p e r i n g , a t t a c h e d stalk ( F i g u r e 12.11C). Lepadocystis moorei ( M e e k ) is found only in the

Elkhorn

Formation (Richmondian).

This

r h o m b i f e r a n h a s a r o u n d e d t h e c a a n d a shorter, t a p e r i n g u n a t t a c h e d stalk ( S u m r a l l a n d S p r i n k l e 1999; F i g u r e s 12.11A, B , D ) . S o m e c o m p l e t e s p e c i m e n s are still a t t a c h e d by a h o l d f a s t c e m e n t e d to v a r i o u s o b j e c t s .

E-drioasteroids N e x t t o t h e c r i n o i d s , e d r i o a s t e r o i d s a r e t h e m o s t c o m m o n e c h i n o d e r m fossils in C i n c i n n a t i a n strata. E d r i o a s t e r o i d s c o n s t i t u t e a class of e c h i n o d e r m s that o r i g i n a t e d d u r i n g t h e C a m b r i a n a n d b e c a m e e x t i n c t i n the P e r m i a n . At first g l a n c e , an e d r i o a s t e r o i d r e s e m b l e s a sea star w i t h a r i n g a r o u n d it

786

A Sea without Fish

Echinoderms

187

(the n a m e m e a n s "seated-star"). T h e sea star r e s e m b l a n c e derives from the five u s u a l l y c u r v i n g food g r o o v e s o r a m b u l a c r a ! tracts that c o n v e r g e o n the c e n t r a l m o u t h ( F i g u r e 12.12). T h i n , o v e r l a p p i n g c a l c i t i c plates c a l l e d intera m b u l a c r a l s take u p t h e s p a c e b e t w e e n t h e a m b u l a c r a . A m o r e rigid series o f m a r g i n a l plates f o r m s t h e ring. U s u a l l y t h e a m b u l a c r a l a n d i n t e r a m b u lacral plates a p p e a r to h a v e c o l l a p s e d inside t h e m a r g i n a l r i n g ; thus it is a s s u m e d that t h e m u l t i p l a t e d t h e c a was flexible in life. Rarely, u n c o l l a p s e d o r " i n f l a t e d " s p e c i m e n s are f o u n d that reveal h o w the a n i m a l probably a p p e a r e d i n life. M o s t C i n c i n n a t i a n e d r i o a s t e r o i d s h a d a l o w d o m e s h a p e , b u t s o m e w e r e m o r e c y l i n d r i c a l ( S u m r a l l 1994). A total of six g e n e r a a n d e l e v e n s p e c i e s are k n o w n f r o m C i n c i n n a t i a n strata ( F i g u r e 12.13). B e c a u s e e d r i o a s t e r o i d s are e x t i n c t , their m o d e o f life m u s t b e inferred b y a n a l o g v t o l i v i n g e c h i n o d e r m s . F d r i o a s t e r o i d s are a l w a y s f o u n d a t t a c h e d to a hard surface s u c h as a b r a c h i o p o d shell, b r y o z o a n , or hardground. T h e lower surface was plated in s o m e species, but in C i n c i n n a t i a n species app a r e n t l y o n l y a soft tissue m e m b r a n e s e r v e d to a d h e r e to the s u b s t r a t u m , possibly i n t h e w a y sea a n e m o n e s a t t a c h b y their p e d a l disk. S o m e s p e c i e s a c t u a l l y c e m e n t e d t o t h e s u b s t r a t u m like a b a r n a c l e , but those a d h e r i n g b y a basal m e m b r a n e m a y have b e e n capable of limited m o v e m e n t . B e c a u s e t h e m o u t h a n d a m b u l a c r a l tracts are d i r e c t e d u p w a r d s i n e d r i o a s t e r o i d s , t h e y a p p a r e n t l y l i v e d a s passive filter f e e d e r s . T h e a m b u l a c r a l g r o o v e s are l i n e d w i t h tinv, z i p p e r - l i k e e o v e r p l a t e s c a p a b l e o f o p e n i n g a n d c l o s i n g (Figu r e 12.12). O p e n i n g t h e e o v e r p l a t e s e x p o s e d t h e food g r o o v e l i n e d w i t h t u b e feet and/or c i l i a that s e r v e d t o c o l l e c t s u s p e n d e d food p a r t i c l e s a n d c o n v e y t h e m t o t h e m o u t h i n a m a n n e r s i m i l a r t o that o f l i v i n g c r i n o i d s . Fecal waste was expelled t h r o u g h a valve-like anal o p e n i n g on the thecal s u r f a c e . T w o o t h e r o p e n i n g s l o c a t e d n e a r t h e m o u t h are a s s u m e d t o b e a g o n o p o r e (for r e l e a s e o f g a m e t e s ) a n d a h y d r o p o r e .

The hydropore allowed

for w a t e r i n t a k e t o t h e w a t e r v a s c u l a r s y s t e m a n d for c o n t r o l o f t h e a m o u n t o f t h e c a l i n f l a t i o n . C y l i n d r i c a l f o r m s s u c h a s t h e C i n c i n n a t i a n Streptaster w e r e c a p a b l e o f t e l e s c o p i n g t h e t h e c a l plates d u r i n g inflation s o a s t o a c h i e v e a n e l e v a t e d f e e d i n g p o s i t i o n a n d d u r i n g d e f l a t i o n a s s u m i n g a lowprofile, p r o t e c t i v e p o s i t i o n ( S u m r a l l 1994). A l t h o u g h e d r i o a s t e r o i d s a r e u s u a l l y c o n s i d e r e d t o b e rare fossils, t h e y c a n occasionally be found by the h u n d r e d s or thousands in C i n c i n n a t i a n strata w h e n t h e a p p r o p r i a t e p r e s e r v a t i o n a l c o n d i t i o n s are p r e s e n t ( M e y e r 1990). T h i n l i m e s t o n e s c o v e r e d w i t h s t r o p h o m e n i d b r a c h i o p o d s (shell p a v e m e n t s ) o r h a r d g r o u n d s ( c a l c a r e o u s s e d i m e n t s l i t h i h e d o n t h e sea f l o o r ) are t h e ideal substrata for e d r i o a s t e r o i d s ( W i l s o n 1985). D e s p i t e the a b u n d a n c e of these types of beds in the C i n c i n n a t i a n , edrioasteroid-bearing p a v e m e n t s are rare. P r e s e r v a t i o n of e d r i o a s t e r o i d s in their life p o s i t i o n on p a v e m e n t s r e q u i r e d a rapid, c a t a s t r o p h i c b u r i a l w i t h f i n e m u d . W i t h o u t s u c h a rapid s m o t h e r i n g , t h e d e l i c a t e , m u l t i p l a t e d e d r i o a s t c r o i d t h e c a disa r t i c u l a t e d s o o n after d e a t h , l e a v i n g little o r n o trace. The d i s c o v e r y of p a v e m e n t s b e a r i n g a b u n d a n t edrioasteroids in the C i n c i n n a t i a n led to p i o n e e r i n g s t u d i e s of t h e life history of edrioasteroids and their p o p u l a t i o n p a l e o e c o l o g v .

Because pavements contained specimens

r a n g i n g in size from a few m i l l i m e t e r s in d i a m e t e r to the largest individuals

188

A Sea without Fish

over thirty m i l l i m e t e r s in d i a m e t e r , Bell (1976) was able to d e t e r m i n e how several s p e c i e s c h a n g e d i n m o r p h o l o g y d u r i n g g r o w t h . T h i s i n f o r m a t i o n w a s used by M e y e r (1990) to study t h e p o p u l a t i o n p a l c o e c o l o g y of t h r e e different species f o u n d o n a s i n g l e p a v e m e n t . S m a l l i n d i v i d u a l s o f the c o m m o n species Isorophus cincinnatiensis ( F i g u r e s 12.13A, B) clustered n e a r t h e m a r g i n s of articulated (likely living) shells of t h e host b r a c h i o p o d Rafinesquina. T h e small edrioasteroids m a y h a v e lived in a c o m m e n s a l r e l a t i o n s h i p w i t h the living b r a c h i o p o d , t a k i n g a d v a n t a g e o f t h e f e e d i n g c u r r e n t s g e n e r a t e d b y t h e b r a c h i o p o d and protection a l o n g the o v e r h a n g i n g m a r g i n o f the host shell. B e c a u s e a single large Isorophus o c c u p i e s a l m o s t an entire b r a c h i o p o d shell, it is likely that either m o r t a l i t y or r e l o c a t i o n to avoid o v e r c r o w d i n g d e p l e t e d the juvenile clusters. In t i m e , t h e edrioasteroids m a y h a v e o u t l i v e d t h e brac h i o p o d host, b e c a u s e t h e larger i n d i v i d u a l s are f o u n d o n d i s a r t i c u l a t e d , abraded ( h e n c e d e a d ) host shells. P a v e m e n t s f o u n d at different stratigraphic h o r i z o n s i n t h e C i n c i n n a t i a n h a v e different edrioasteroid s p e c i e s p o p u l a tions ( S u m r a l l et al. 2001).

Asteroids S e a stars are e x c e p t i o n a l l y rare fossils in t h e C i n c i n n a t i a n ; o f t e n , s p e c i m e n s are hard to r e c o g n i z e b e c a u s e they are f r a g m e n t a r y or distorted. N e v e r t h e less, six g e n e r a a n d ten s p e c i e s are valid f r o m the C i n c i n n a t i a n ( F i g u r e s 12.14-12.16). S e a stars are t h e m o s t r e c o g n i z a b l e e c h i n o d e n n s , h a v i n g the stereotypical pentaradial s y m m e t r y . they differ from brittle stars (ophiuroids) in h a v i n g a r m s that are not sharply differentiated f r o m t h e c e n t r a l disk. C i n c i n n a t i a n sea stars, like m o d e r n f o r m s (Plate 9 E ) , h a d a w i d e r a n g e o f b o d y f o r m s that c a n b e related t o a diversity o f f e e d i n g habits. T h e bestk n o w n C i n c i n n a t i a n sea star, Promopalaeaster, stratigraphic

section.

An

extraordinary

is f o u n d t h r o u g h o u t t h e

specimen

of a

Promopalaeaster

w r a p p e d a r o u n d a b i v a l v e m o l l u s c p r o v i d e s a rare e x a m p l e of a sea star c a u g h t i n a n a n c i e n t act o f p r e d a t i o n ( F i g u r e 12.15D; B l a k e a n d G u e n s b u r g 1994). This c a s e d e m o n s t r a t e s that s o m e sea stars o f t h e O r d o v i c i a n h a d t h e ability t o prey o n p e l e c y p o d s b y p r y i n g t h e i r v a l v e s a p a r t just a s d o m o d e r n sea stars.

T h e s t o m a c h is e v e r t e d t h r o u g h t h e m o u t h a n d t h e p r e v is d i -

g e s t e d w i t h i n its o w n s h e l l .

B r a n s t r a t o r (1975) c o n c l u d e d that Mesopa-

laeaster w a s a l s o a s t o m a c h - e v e r t i n g sea star. Hudsonaster is a s m a l l sea star with large, b l o c k y plates, at least s u p e r f i c i a l l y s i m i l a r to c e r t a i n p r e s e n t - d a y m e m b e r s o f t h e G o n i a s t e r i d a e o r O p h i d i a s t e r i d a e , w h i c h f e e d o n passive, c o l o n i a l o r g a n i s m s , s m a l l prey, a n d d e t r i t u s ( F i g u r e 12.16A; J a n g o u x 1982). Another

Cincinnatian

asteroid,

Petraster speciosus

(Richmondian),

has

short, broad a r m s a n d a flattened profile ( F i g u r e 12.15C). It is v e r y s i m i l a r t o m o d e r n sea stars that live b y i n g e s t i n g s e d i m e n t a n d d i g e s t i n g o r g a n i c materials ( B l a k e a n d G u e n s b u r g 1988). In c o n t r a s t , Salteraster h a d v e r y l o n g , n a r r o w a r m s , w ith s m a l l ossicles ( F i g u r e 12.15E). S p e c i m e n s are often p r e s e r v e d in a c o n t o r t e d m a n n e r s u g g e s t i n g great flexibility a n d ability to handle small

or large

prey.

Both

Salteraster a n d

Lanthanaster ( F i g u r e s

12.15A, B) are t h o u g h t to h a v e b u r r o w e d into fine s e d i m e n t in s e a r c h of

Echinoderms

prey, a n d b o t h m a y h a v e p r o d u c e d the rare star-shaped b u r r o w s i n the C i n c i n n a t i a n c a l l e d Asteriacites (see F i g u r e 14.3D; Branstrator 1975).

Ophiuroids T h e o p h i u r o i d s (brittle stars o r s e r p e n t stars) a r e d i s t i n g u i s h e d from the asteroids b y h a v i n g t h e f i v e a r m s sharply differentiated from t h e c e n t r a l disk (Plate 9 C ) . T h e a r m s are q u i t e flexible b e c a u s e t h e y a r e c o m p o s e d o f a series of vertebra-like ossicles c o n n e c t e d by m u s c l e s a n d l i g a m e n t s . O p h i uroids c a n m o v e q u i t e rapidly o n t h e sea floor b y l a s h i n g t h e a r m s and s o m e c a n flex t h e a r m s v e r t i c a l l y a s w e l l . T h e a r m s are e q u i p p e d w i t h t u b e feet that are u s e d to g a t h e r o r g a n i c p a r t i c l e s either d i r e c t l y from t h e sedim e n t o r a s s u s p e n d e d p a r t i c l e s . O p h i u r o i d s a r e usually c o n s i d e r e d t o b e d e p o s i t f e e d e r s , b u t s o m e are also c a p a b l e o f s u s p e n s i o n f e e d i n g a n d e v e n predation.

Taeniaster spinosus

(Billings)

occurs

in

the

Cincinnatian

( I l o t c h k i s s 1970; F i g u r e 12.16B), a n d like asteroids, it is very rare. M o d e r n o p h i u r o i d s c a n live in v e r y d e n s e a g g r e g a t i o n s on the sea floor. Rarely slabs h a v e b e e n f o u n d in t h e C i n c i n n a t i a n b e a r i n g d e n s e a s s e m b l a g e s of Taeniaster, s u g g e s t i n g that a g g r e g a t i o n b e h a v i o r w a s a c h i e v e d in this very early m e m b e r of the group. In the only other k n o w n C i n c i n n a t i a n ophiuroid, Protasterina flexuosa, p y r i t i z e d t u b e feet h a v e b e e n reported in a s p e c i m e n f r o m t h e K o p e F o r m a t i o n ( G l a s s 2006).

Cyclocystoids T h e c y c l o c y s t o i d s are a m o n g the rarest a n d m o s t e n i g m a t i c o f C i n c i n n a tian e c h i n o d e r m s . T h e y c a n b e easily m i s t a k e n for a n edrioasteroid b e c a u s e t h e y h a d a c i r c l e t o f s q u a r i s h , m a r g i n a l plates, 7 - 2 0 m m i n d i a m e t e r , but lack t h e c h a r a c t e r i s t i c f i v e c u r v i n g a m b u l a c r a o f edrioasteroids ( F i g u r e 12.16C). A c o m p r e h e n s i v e study of c y c l o c y s t o i d s by S m i t h a n d Paul (1982) p r o v i d e s t h e m o s t u p t o date u n d e r s t a n d i n g o f their c o m p l e x m o r p h o l o g y . T h e skeleton of a c y c l o c y s t o i d c o n s i s t s of t h r e e parts: a c e n t r a l disk, a m a r g i n a l r i n g , a n d a p e r i p h e r a l skirt. U s u a l l y o n l y t h e m a r g i n a l r i n g is f o u n d , c o n s i s t i n g o f e i g h t e e n t o sixty s q u a r i s h o r b l o c k v ossicles. N u m e r o u s s m a l l plates c o v e r o n e s u r f a c e o f t h e disk: g r o o v e d radial plates, u n g r o o v e d interradial plates, a n d c o v e r plates c o v e r i n g t h e g r o o v e d radial plates. T h e r e is a c e n t r a l o p e n i n g o n this s u r f a c e , p r e s u m a b l y the m o u t h . S m a l l p o l y g o n a l plates c o v e r t h e o p p o s i t e s u r f a c e , w i t h a s m a l l c o n e at the c e n t e r , p r e s u m ably s u r r o u n d i n g t h e a n a l o p e n i n g . A l t h o u g h s o m e c y c l o c y s t o i d s h a v e f i v e fold s y m m e t r y o f t h e p l a t i n g , o t h e r s h a v e four-fold o r six-fold s y m m e t r y , b r e a k i n g the s t e r e o t y p i c a l e c h i n o d e r m p a t t e r n .

The n a t u r e o f t h e p l a t i n g

s u g g e s t s t h a t i n life, t h e r e w a s v e r y little b o d y s p a c e b e t w e e n the t w o plated s u r f a c e s . The m a r g i n a l ossicles h a v e a d i s t i n c t i v e f o r m a n d are perforated b y tiny c a n a l s . E a c h m a r g i n a l has o n e t o seven c u p u l c s , w h i c h a r e s p o o n s h a p e d d e p r e s s i o n s . E a c h c u p u l e l e a d s to a radial d u c t l y i n g w i t h i n a circ u m f e r e n t i a l g r o o v e . T h e p e r i p h e r a l skirt consists o f s m a l l , i m b r i c a t e plates that c o v e r e d t h e r i n g o f c u p u l e s i n life.

190

A Sea without Fish

B e c a u s e t h e r e a p p e a r s t o h a v e b e e n very little s p a c e b e t w e e n t h e plated s u r f a c e s o f the l i v i n g c v c l o e y s t o i d , t h e a n i m a l s o m e w h a t r e s e m b l e d a t a m b o u r i n e rather t h a n a d r u m . L a c k i n g internal s p a c e for o r g a n s , c y c l o cystoids w e r e restricted t o f e e d i n g o n m i n u t e o r g a n i c p a r t i c l e s . S m i t h a n d Paul c o n c l u d e that the p a r t i c l e s w e r e c o l l e c t e d a t t h e c u p u l e s b y c i l i a r y a c t i o n a n d c o n v e y e d via the d u c t s t o t h e radial g r o o v e s that c o n v e r g e d o n t h e c e n t r a l m o u t h . A l t h o u g h t u b e feet are n o t p r e s e r v e d , S m i t h a n d P a u l suggest that t u b e feet c o u l d h a v e e m e r g e d f r o m p o r e s b e t w e e n plates o n the ventral s u r f a c e a n d p r o v i d e d a m e a n s o f l o c o m o t i o n . T h e e y c l o c v s t o i d thus m o v e d over the substrate a n d g a t h e r e d o r g a n i c p a r t i c l e s u s i n g c i l i a t e d c u p u l e s . O t h e r s p e c i a l i s t s , h o w e v e r , d o not a c c e p t t h e life o r i e n t a t i o n favored by S m i t h a n d Paul, a n d instead regard the o p p o s i t e side as l o w e r m o s t ( S p r i n k l e , pers. c o m m . ) C y c l o c y s t o i d s f i r s t a p p e a r e d i n t h e Farlv O r d o v i c i a n a n d last in the Late D e v o n i a n or Karlv C a r b o n i f e r o u s ( S m i t h a n d Paul 1982). A total of n i n e g e n e r a a n d f o r t y - o n e s p e c i e s h a v e b e e n d e s c r i b e d . In the C i n c i n n a t i a n , three g e n e r a a n d f i v e s p e c i e s a r e k n o w n .

Stvlophorans f o r m a n y p a l e o n t o l o g i s t s , s t v l o p h o r a n s surpass e v e n the c y c l o c y s t o i d s a s s o m e o f t h e m o s t b i z a r r e fossil e c h i n o d e r m s . For a m i n o r i t y o f s p e c i a l i s t s , s t v l o p h o r a n s are c o n s i d e r e d not e v e n t o h e e c h i n o d e r m s , b u t rather a n c e s tors of t h e vertebrates b e l o n g i n g to a g r o u p c a l l e d c a l c i c h o r d a t e s . ( T h e interested reader is referred to G e e 119961 for a b l o w - b y - b l o w a c c o u n t of this debate.)

This c o n t r o v e r s y , c o u p l e d w i t h their e x c e e d i n g rarity i n C i n -

c i n n a t i a n strata, m a k e the s t v l o p h o r a n s o n e o f the m o s t i n t r i g u i n g fossils ever to be f o u n d in the C i n c i n n a t i r e g i o n . A s i n g l e g e n u s , Enoploura, is f o u n d in the C i n c i n n a t i a n , w i t h M a v s v i l l i a n ( F i g u r e 12.17)

a n c

'

t w o s p e c i e s , E. popei C a s t e r in

the

balanoides 1 M e e k ) in the Mavsv illian a n d

R i c h m o n d i a n ( C a s t e r 19S2; Parsley 1991). Enoploura is t y p i c a l of the s t v l o p h o r a n s , an e x t i n c t e c h i n o d e r m class that r a n g e s from t h e M i d d l e C a m b r i a n t h r o u g h t h e E a r l y P e n n s v l v a n i a n , with a b o u t e i g h t y g e n e r a in all. Enoploura has a flattened, p l a t e d t h e c a that i s r o u g h l y r e c t a n g u l a r ; the p l a t i n g has n o radial o r p e n t a m e r a l s y m m e t r y w h a t s o e v e r , hut rather is bilaterally s y m m e t r i c a l . A p a i r of s p i n e s is attached at one end, and at the opposite end, a single, s e g m e n t e d a p p e n d a g e is a t t a c h e d . This a p p e n d a g e has a very c o m p l e x s t r u c t u r e a n d its f u n c t i o n has b e e n v i g o r o u s l y d e b a t e d . Il was o n c e t h o u g h t to be a stalk-like h o l d f a s t , but those f a v o r i n g the e c h i n o d e r m affinity of (he s t v l o p h o r a n s c o n s i d e r it to be a feeding a p p e n d a g e , called the a u l a c o p h o r e .

T h e basal p a r t o f t h e

a u l a c o p h o r e i s m a d e u p o f a series o f t h i n e l e m e n t s e a c h c o n s i s t i n g o f four c o m p o n e n t s ; il was p r o b a b l y flexible. F o l l o w i n g this flexible r e g i o n is t h e s o - c a l l e d styloid, b e a r i n g a pair of b l a d e l i k e flanges that p r e s u m a b l y d u g into the s e d i m e n t .

The t e r m i n a l p a r t o f t h e a u l a c o p h o r e has a t a p e r i n g

series o f sharply k e e l e d ossicles b e a r i n g a g r o o v e w i t h c o v e r i n g plates. T w o possible f e e d i n g positions h a v e b e e n p o s t u l a t e d for t h e a u l a c o p h o r e : h e l d up into the water or a r c h e d slightly a b o v e t h e s u b s t r a t u m . In a n y c a s e t h e food consisted of very tine o r g a n i c p a r t i c l e s . Particles taken in a l o n g a food

Echinoderms

191

groove entered an internal m o u t h , and wastes were emitted through an a n a l o p e n i n g b e t w e e n t h e s p i n e s . P r o p o n e n t s o f t h e e a l c i c h o r d a t e interp r e t a t i o n of s t v l o p h o r a n s regard t h e a p p e n d a g e to be a t r u e , w r i g g l i n g tail, with the m o u t h located at the opposite end of the theca. Study of wellp r e s e r v e d skeletal m i c r o s t r u c t u r e in C i n c i n n a t i a n V.noploura by C a r l s o n a n d f i s h e r (1981) r e v e a l e d c l o s e s i m i l a r i t y t o t y p i c a l e c h i n o d e r m s t c r e o m , further supporting the classification of stvlophorans with e c h i n o d e r m s . S o m e e n i g m a t i c fossils c a l l e d m a e h a e r i d i a n s m i g h t also b e related t o stvl o p h o r a n s (see c h a p t e r 10).

192

A Sea without Fish

194

A Sea without Fish

GRAPTOLITES AND CONODONTS: OUR CLOSEST RELATIVES?

G r a p t o l i t e s are a m o n g t h e m o s t d i s t i n c t i v e fossils f o u n d i n C i n c i n n a t i a n

Graptolites

strata a n d are also u n i q u e l y s i g n i f i c a n t . C r a p t o l i t e s are c o m m o n l y preserved in shales in a h i g h l y flattened c o n d i t i o n , a p p e a r i n g like b l a c k p e n c i l m a r k i n g s w i t h a s a w - t o o t h e d m a r g i n (the n a m e g r a p t o l i t e i n fact m e a n s " w r i t t e n stone"; F i g u r e 1 3 . l C ) . I n s o m e C i n c i n n a t i a n l i m e s t o n e s g r a p t o l i t e s can be preserved in an u n c o m p a c t e d , three-dimensional condition. B e c a u s e their skeletal s t r u c t u r e ( p e r i d e r m ) i s o r g a n i c t h e s e " i n f l a t e d " g r a p t o lites c a n b e e t c h e d free o f t h e m a t r i x u s i n g a c i d t o r e v e a l e x c e p t i o n a l s t r u c tural details ( F i g u r e 13.1B). G r a p t o l i t e s r e p r e s e n t t h e skeletal s h e a t h of a c o l o n i a l , soft-bodied m a r i n e invertebrate w h o s e soft parts are n o t p r e s e r v e d . G r a p t o l i t e c o l o n i e s existed a s f r e e - f l o a t i n g p l a n k t o n (order G r a p t o l o i d e a ) o r a s b r a n c h i n g , b e n t h i c c o l o n i e s (order D e n d r o i d e a ) . T h e c o l o n i a l skeleton ( r h a b d o s o m e ) h o u s e d m a n y s o f t - b o d i e d z o o i d s e a c h w i t h i n a c u p - l i k e t h e c a ( F i g u r e 13.1A). T h e w a l l s o f t h e t h e c a e are c o n s t r u c t e d i n a u n i q u e w a y that i s o f g r e a t i m p o r t a n c e i n e s t a b l i s h i n g t h e n a t u r e o f t h e g r a p t o l i t e

Figure 13.1.

o r g a n i s m : narrow

lite

h a l f - r i n g s (fusellae) a l t e r n a t e t o f o r m a z i g z a g s u t u r e

A.

morphology.

a l o n g the t h e c a l t u b e . A n o u t e r c o r t i c a l layer o f c o l l a g e n fibrils r e i n f o r c e s

by Kevina Vulinec.

the fusellar layer b y c r i s s - c r o s s i n g t h e s u r f a c e ; h e n c e t h e s e are c a l l e d c o r t i -

C.

typicalis (Hall).

stipes either in a s i n g l e l i n e a r series ( m o n o s e r i a l ) , a d o u b l e Series (biserial),

gle

by t h e t h r e a d - l i k e n e m a to v a n e - l i k e s t r u c t u r e s or p o s s i b l y to gas-filled bulbs that p r o v i d e d flotation. A l t h o u g h i t w a s o n c e t h o u g h t that g r a p t o l o i d s attached by m e a n s of the n e m a to other floating material like s e a w e e d , it i s n o w g e n e r a l l y a c c e p t e d that p l a n k t i c g r a p t o l o i d s u s e d t h e i r o w n m e a n s

Sin-

courtesy

Goldman.

Cluster of partly paral-

lel-oriented MUGM 29469,

rhabdosomes, Cincinna-

tian, Butler Co., Ohio, scale in mm.

of flotation, b u t t h e r e is d e b a t e as to w h e t h e r flotation w a s a c t i v e l y or p a s sively m a i n t a i n e d ( R i g b y a n d Fortey 1991). T h e f l o a t i n g ability o f g r a p t o l o i d s c a u s e d t h e m t o b e c a r r i e d g r e a t distances by o c e a n currents. C o n s e q u e n t l y a single graptolite species c a n b e f o u n d o v e r a vast g e o g r a p h i c a r e a , e v e n o n s e p a r a t e c o n t i n e n t s . T h i s w i d e d i s t r i b u t i o n , c o u p l e d w i t h t h e i r relatively rapid e v o l u t i o n a r y c h a n g e over t i m e , m a k e graptolites s o m e o f t h e m o s t ideal i n d e x fossils for biostratig r a p h i c z o n a t i o n a n d c o r r e l a t i o n o f strata. G r a p t o l i t e s f i r s t a p p e a r e d i n t h e Middle C a m b r i a n and b e c a m e extinct as a group in the Pennsylvanian, b u t for O r d o v i c i a n a n d S i l u r i a n strata in p a r t i c u l a r , g r a p t o l i t e s ( a l o n g w i t h c o n o d o n t s ) p r o v i d e t h e e s s e n t i a l basis for relative a g e d a t i n g a n d c o r r e l a tion w o r l d w i d e .

B.

rhabdosome,

of Daniel C.

B,

Geniculograptus

cal b a n d a g e s . I n p l a n k t i c g r a p t o l o i d s , t h e c a e are a r r a n g e d a s b r a n c h e s o r or e v e n triserial or q u a d r i s e r i a l . S t i p e s w e r e a t t a c h e d s i n g l y or in m u l t i p l e s

GraptoDrawing

The U p p e r O r d o v i c i a n o f N o r t h A m e r i c a i s d i v i d e d into

four graptolite b i o z o n e s o n t h e basis o f o v e r l a p p i n g r a n g e s o f several s p e c i e s ( G o l d m a n a n d B e r g s t r o m 1997).

195

Figure

1 3 . 2 . Cincinnatian

conodonts.

Those

are among common from

the most

forms.

the

dian

shown

m o s t c o m m o n a n d c h a r a c t e r i s t i c C i n c i n n a t i a n graptolite i s Geniculogrcip-

All are

lower Riehmon-

Stage near

Brookville,

Franklin

Indiana.

Co.,

A, G, H.

todina

tenuis

\ l t h o u g h several s p e c i e s of graptolites o c c u r in the C i n c i n n a t i a n of t h e C i n c i n n a t i A r c h r e g i o n , o n l y a few are c o m m o n ( B e r g s t r o m 1997). The

Plec-

tus (identified as Climacograptus in o l d e r literature; f i g u r e s 13.1B, C ) . T h i s g r a p t o l i t e has a hiserial r h a b d o s o m e a n d is very c h a r a c t e r i s t i c of t h e K o p e f o r m a t i o n , w h e r e a g g r e g a t i o n s o f stipes often o c c u r i n p a r a l l e l a l i g n m e n t o n b e d d i n g s u r f a c e s ( f i g u r e 13.1C). T w o s p e c i e s r a n g e from t h e K o p e

(Branson

t h r o u g h F a i r v i e w f o r m a t i o n s ( B e r g s t r o m 1996a). ' I w o hiserial graptolites

and Mehl).

A.

Pb ele-

o c c u r in t h e A r n h e i m f o r m a t i o n ( R i e h m o n d i a n ) : Orthogrciptus qucidrimu-

ment.

M element.

cronatus a n d Arnheimograptus anacanthus (see B e r g s t r o m 1996a). S e v e r a l

G.

H.

Sc element.

s p e c i e s of Mastigograptus, a d e l i c a t e , b u s h - l i k e d e n d r o i d graptolite, o c c u r

B. Oulodus

oregonia

(Branson,

Mehl,

Branson),

Pb

C,

D.

thus

and

Amorphogna-

son and Mehl. element.

BranC.

D.

ment. dus

E.

and Mehl). modus

g r o u p ( B u l i n a n 1970). R e s e a r c h b y t h e Polish p a l e o n t o l o g i s t R o m a n K o z l o w s k i (1966) n o t e d several s i m i l a r i t i e s b e t w e e n graptolites a n d the l i v i n g

(Branson

h e m i c h o r d a t e s c a l l e d p t e r o b r a n c h s that a r g u e stronglv for a c l o s e e v o l u -

Phrag-

undatus

Branson

S element.

I

Rhodesognathus

egans

(Rhodes),

ment.

J.

Pb

tron

Scanning

micrographs

tesy of Stig M. strom, 130.

apparatus, S

M

elements

series

are

elements,

ing position in

sellar h a l f - r i n g a n d c o r t i c a l s t r u c t u r e f o u n d i n graptolites ( B u l i n a n 1970).

pterobranchs that interconnects zooids within the colony.

The identifica-

tion of the protein c o l l a g e n in the tubes of both graptolites and pterox

the

elements

medial elements,

c o n s t r u c t e d by t h e l i v i n g p t e r o b r a n c h Rhabdopleura has the u n i q u e fu-

elec-

a and b in

P h y l u m 1 l e m i c h o r d a t a o n t h e basis o f e m b r y o l o g i c a l s i m i l a r i t i e s ; there are o n l y t h r e e liv i n g g e n e r a o f p t e r o b r a n c h s ( B a r n e s 19S7). T h e c r e e p i n g t u b e

In a d d i t i o n , some e n c r u s t i n g t y p e s of g r a p t o l i t e s h a v e a b l a c k stolon pre-

Berg-

denoting position

i n g i n v e r t e b r a t e s t h a t are c l a s s e d t o g e t h e r w i t h t h e a c o r n w o r m s i n t h e

s e r v e d w i t h i n t h e t u b e s that is verv s i m i l a r to t h e s t r u c t u r e of the stolon in

cour-

approximately

t i o n a r y r e l a t i o n s h i p . P t e r o b r a n c h s are a g r o u p o f s m a l l , m a r i n e , t u b e - d w e l l -

Pb

P elements are prin-

cipal elements,

are

ele-

Branson,

Mehl and Branson, element.

el-

Aphelogna-

grandis

w i t h several d i f f e r e n t g r o u p s , i n c l u d i n g c e p h a l o p o d s , c n i d a r i a n s , b r y o z o ans, and hemichordates, or were considered to be unrelated to any living

DrepanoistoF.

and Mehl,

Sc

most c h a l l e n g i n g p r o b l e m s i n p a l e o n t o l o g y . G r a p t o l i t e s w e r e classified

Pa ele-

suberectus

thus

The z o o l o g i c a l affinities o f g r a p t o l i t e s w e r e for m a n y years a m o n g t h e

element.

ordovicicus

i n the K o p e , A r n h e i m , a n d W a y n e s v i l l e f o r m a t i o n s .

and

symmetry c denot-

b r a n c h s i n d i c a t e s not o n l y their c l o s e r e l a t i o n s h i p , b u t also affinity to chord a t e s , i n w h i c h c o l l a g e n f o r m s t h e c o n n e c t i v e tissue ( A r m s t r o n g e t al. 19S4). T h e e x t i n c t g r a p t o l i t e s a r e t h u s g e n e r a l l y treated a s a n e x t i n c t class w i t h i n the 1 l e m i c h o r d a t a . A l t h o u g h t h e soft part s t r u c t u r e of t h e graptolite z o o i d s r e m a i n s u n k n o w n , h y p o t h e t i c a l r e c o n s t r u c t i o n s s u g g e s t that the z o o i d s p r o b a b l y h a d p a i r e d t e n t a c l e - b e a r i n g a r m s that w e r e e x t e n d e d for purposes of suspension feeding and deposition of the outer cortical band a g e s o f the t h e c a l w a l l .

the

apparatus.

Conodonts

It is i r o n i c that p e r h a p s t h e m o s t s i g n i f i c a n t C i n c i n n a t i a n fossils, in a g e o l o g i c a l s e n s e , a r e a l s o a m o n g t h e least c o n s p i c u o u s t o m o s t o b s e r v e r s . T h e s e are t h e c o n o d o n t s , t o o t h - l i k e m i c r o f o s s i l s ( < 1 m m ) , s o u n l i k e a n y o t h e r fossil or l i v i n g o r g a n i s m s that they w e r e r e g a r d e d until r e c e n t l y as r e p r e s e n t i n g a d i s t i n c t p h y l u m . C o n o d o n t s c a n b e f o u n d t h r o u g h o u t the C i n c i n n a t i a n by dissolving blocks of limestone in acetic acid, although they c a n also be found in disaggregated shales. B e c a u s e conodonts have a c a l c i u m p h o s p h a t e c o m p o s i t i o n , t h e y a r e i n s o l u b l e i n a c e t i c acid. C o n o d o n t s are c o n s p i c u o u s in t h e a c i d - i n s o l u b l e r e s i d u e s c a n n e d u n d e r a dis-

196

A Sea without Fish

Graptolites and Conodonts

197

secting m i c r o s c o p e b e c a u s e of their u n i q u e forms and a beautiful a m b e r c o l o r (Plate 5B). C o n o d o n t s h a v e a w i d e r a n g e o f s h a p e s , i n c l u d i n g single c o n e s , m u l t i p r o n g e d " t e e t h , " serrated b l a d e - l i k e s h a p e s , a n d s o - c a l l e d p l a t f o r m - t y p e f o r m s ( F i g u r e 13.2). M o s t c o n o d o n t s h a v e a tooth-like a p p e a r a n c e , l e a d i n g to t h e a s s u m p t i o n that t h e y w e r e u s e d a s t e e t h . H o w e v e r , c o n o d o n t s also s h o w r e g e n e r a t i o n . This s u g g e s t s that at least s o m e c o n o d o n t s w e r e e m b e d d e d in soft tissue b y w h i c h t h e y w e r e s e c r e t e d . I n d i v i d u a l c o n o d o n t s , c a l l e d elem e n t s , w e r e g i v e n s p e c i e s n a m e s b y earlier workers. H o w e v e r , the discovery of rarely p r e s e r v e d a s s e m b l a g e s of different e l e m e n t s in rock matrix or fused t o g e t h e r led to t h e r e c o g n i t i o n that e l e m e n t s w e r e a r r a n g e d in bilaterally s y m m e t r i c a l a s s e m b l a g e s o f pairs o f e l e m e n t s , e a c h o f w h i c h i s c a l l e d a n a p p a r a t u s . A l t h o u g h few a p p a r a t u s e s are preserved intact, it has b e e n possible to d e t e r m i n e w h i c h e l e m e n t s f o u n d in a s a m p l e likely f o r m e d an apparatus o n t h e basis o f statistical analysis o f the ratios o f c o m m o n l y associated e l e m e n t s . M o d e r n t a x o n o m i s t s o f c o n o d o n t s a t t e m p t t o i n c l u d e t h e six o r s e v e n different e l e m e n t s of a g i v e n a p p a r a t u s u n d e r a single species n a m e . B e c a u s e the tooth-like elements apparently were the only mineralized parts o f t h e o r g a n i s m , t h e i d e n t i t y o f t h e c o n o d o n t - b e a r i n g o r g a n i s m a n d t h e n a t u r e o f its soft p a r t a n a t o m y h a v e b e e n a m o n g t h e great m y s t e r i e s o f p a l e o n t o l o g y . A m a j o r b r e a k t h r o u g h c a m e in 1983 w h e n a fossil of an e e l like, s o f t - b o d i e d o r g a n i s m f r o m t h e L o w e r C a r b o n i f e r o u s o f S c o t l a n d w a s s h o w n t o h a v e a c o n o d o n t a p p a r a t u s a t o n e e n d a n d fin-like s t r u c t u r e s a t t h e o p p o s i t e ( B r i g g s e t al. 11)83). T h i s " c o n o d o n t a n i m a l " i s o n l y 4 c m l o n g a n d s h o w s little of its i n t e r n a l a n a t o m y , save for a m i d l i n e s u g g e s t i n g bilateral s y m m e t r y . A l t h o u g h i t b e a r s s i m i l a r i t i e s t o b o t h c h a e t o g n a t h s a n d c h o r d a t e s , t h e a u t h o r s c o n c l u d e d that t h e c o n o d o n t a n i m a l b e l o n g s t o a distinct p h y l u m . M o r e recent phylogenetic studies based on more extensive data p l a c e t h e c o n o d o n t s w i t h i n t h e c h o r d a t e s , c l o s e t o t h e l i v i n g l a m p r e y s ( D o n o g h u e e t al. 2000). B e c a u s e c o n o d o n t a n i m a l s h a d m i n e r a l i z e d c a l c i u m p h o s p h a t e e l e m e n t s , a m o n g o t h e r c h a r a c t e r i s t i c s , t h e y are c o n s i d e r e d to be vertebrates, even t h o u g h they lacked internal skeletons. T h e c o n o dont a n i m a l c o u l d be considered to have b e e n the fish of the C i n c i n n a t i a n sea. H o w e v e r , g i v e n t h e i r s m a l l s i z e a n d g r e a t d i f f e r e n c e s from a n y t h i n g like p r e s e n t - d a y b o n y fish, t h e title of this b o o k , A Sea without Fish, rem a i n s v a l i d . T h e f o r e g o i n g i n t r o d u c t i o n i s l a r g e l y b a s e d o n C l a r k (1987). F o r m o r e i n f o r m a t i o n a b o u t t h e m o r p h o l o g y a n d affinities o f c o n o d o n t s t h e r e a d e r s h o u l d c o n s u l t A l d r i d g e e t al. (1993), A l d r i d g e a n d P u r n e l l (1996), a n d D o n o g h u e e t al. (2000). C o n o d o n t s of p a r t i c u l a r t y p e s are f o u n d in m a r i n e rocks over a very w i d e g e o g r a p h i c r a n g e , e v e n i n t e r c o n t i n e n t a l i n extent. T h i s w i d e distribution s u g g e s t e d that t h e c o n o d o n t o r g a n i s m was p e l a g i c l o n g before the f i n b e a r i n g c o n o d o n t a n i m a l w a s d i s c o v e r e d ( C l a r k 1987). C o n o d o n t s apparently lived a s s w i m m i n g m e m b e r s o f t h e m a r i n e n e k t o n r a n g i n g from close t o the sea f l o o r t o v a r i o u s positions i n the w a t e r c o l u m n . T h e tooth-like apparatus m i g h t h a v e b e e n u s e d to s e i z e or strain food items from the water. I n a d d i t i o n t o their w i d e g e o g r a p h i c r a n g e , g e n e r a o f c o n o d o n t s are r e s t r i c t e d i n t h e i r v e r t i c a l (stratigraphic) r a n g e s t h r o u g h o u t their M i d d l e

798

A Sea without Fish

Figure tion

13.3.

of the

ReconstrucOrdovician

jawless fish, As t rasp is desiderata from stone

Walcott,

the Harding Sandof

Colorado.

Length about

13 cm.

From Cowen (2005, figure

7.4).

86,

Reprinted

with

permission

well

Publishing.

of Black-

C a m b r i a n t h r o u g h Triassic g e o l o g i c r e c o r d . T h e s e attributes, t o g e t h e r w i t h a b u n d a n c e i n m a r i n e strata a s m i c r o t o s s i l s , m a k e c o n o d o n t s e x c e p t i o n a l l y useful for b i o s t r a t i g r a p h i c s u b d i v i s i o n o f t h e P a l e o z o i c s e d i m e n t a r y r o c k record. For the entire U p p e r O r d o v i c i a n (above t h e b a s e o f t h e L e x i n g t o n L i m e s t o n e ) in t h e C i n c i n n a t i r e g i o n . S w e e t

(1979)

conodont species representing twenty genera (Figure

r e c o r d e d thirtv-live

13.2).

Most genera

o c c u r also i n E u r o p e , A s i a , A u s t r a l i a , o r A f r i c a , b u t s p e c i e s a r e m o r e g e o g r a p h i c a l l y restricted. Most C i n c i n n a t i a n c o n o d o n t s represent the N o r t h A m e r i c a n M i d c o n t i n c n t P r o v i n c e , b u t s o m e are c o m p o n e n t s o f t h e N o r t h A t l a n t i c P r o v i n c e that is also r e p r e s e n t e d in E u r o p e .

The t y p e - C i n c i n n a -

tian s e c t i o n s p a n s all or parts of six c o n o d o n t - d e f i n e d b i o s t r a t i g r a p h y z o n e s ( W e b b y , C o o p e r , B e r g s t r o m , a n d Paris

2004).

Although many cono-

d o n t taxa h a v e l o n g s t r a t i g r a p h i c r a n g e s w i t h i n t h e C i n c i n n a t i a n , variations in relative a b u n d a n c e are p r o b a b l y related to d i f f e r i n g d e p t h prefere n c e s a m o n g s p e c i e s (Sweet

1979, 1996).

C o n o d o n t s m a y have b e e n the o n l y representatives of the vertebrates in the

Ordovician "fish"

C i n c i n n a t i a n sea, but fossil e v i d e n c e from m a n y localities e l s e w h e r e s h o w s that s o m e of the earliest tish did i n d e e d exist d u r i n g the O r d o v i c i a n Period. T h e O r d o v i c i a n H a r d i n g S a n d s t o n e o f C o l o r a d o c o n t a i n s a b u n d a n t , tiny plates c o m p o s e d of an e n a m e l - c o a t e d d e n t i n e , n a m e d Astnispis desiderata by W a l c o t t in 1892. In 1997 S a n s o n ) and others illustrated an e x t r a o r d i n a r y fossil from the H a r d i n g w i t h a c o m p r e s s e d , n e a r l y c o m p l e t e , fish-like b o d y t h a t proved the l o n g - h e l d a s s u m p t i o n that the tiny plates f o r m e d a h e a d shield (Figure

13.3).

Lyes and a series of o p e n i n g s p r o b a b l y related to respiration are

Qraptolites and Conodonts

199

p r e s e r v e d . A s i m i l a r fossil fish f r o m O r d o v i c i a n rocks in Bolivia shows that t h e s e early fish h a d b l u n t , r o u n d e d h e a d s , an e l o n g a t e d fish-like s h a p e w i t h a tail fin, b u t l a c k e d b o n y jaws a n d separate fins. T h e s e jawless fish are c a l l e d a g n a t h a n s , b u t o t h e r O r d o v i c i a n fossils r e p r e s e n t t h e earliest jawed fish or g n a t h o s t o m e s ( S a n s o m et al. 2001). T h u s , a variety of early fish had already e v o l v e d b y C i n c i n n a t i a n t i m e , b u t t h e y are u n k n o w n from t h e C i n c i n n a t i r e g i o n . H a d t h e s e early fish b e e n present in t h e C i n c i n n a t i a n sea, it w o u l d s e e m r e a s o n a b l e t o e x p e c t their m i n e r a l i z e d plates t o b e p r e s e r v e d i n the l i m e s t o n e s or shales. A l t h o u g h their a b s e n c e m a y indicate that then preferred -

an e n v i r o n m e n t n o t represented in t h e t y p e - C i n c i n n a t i a n , the potential for their e v e n t u a l d i s c o v e r ) s h o u l d not b e o v e r l o o k e d .

200

A Sea without Fish

202

A Sea without Fish

TYPE-CINCINNATI ANTRACE FOSSILS: TRACKS, TRAILS, AND BURROWS

The C i n c i n n a t i a n is r e n o w n e d for its a b u n d a n c e of w e l l - p r e s e r v e d shells and skeletons o f Orclo\ ician m a r i n e invertebrates, a n d b e c a u s e t h e s e fossils represent the r e m a i n s o f l o n g - d e a d o r g a n i s m s , a t first g l a n c e o n e w o u l d n o t e x p e c t t h e m t o yield m u c h i n f o r m a t i o n a b o u t t h e a c t i v i t y a n d b e h a v i o r o f these a n i m a l s d u r i n g life. O f c o u r s e , w e c a n d e d u c e a g r e a t d e a l a b o u t t h e

Figure 14.1.

life habits o f O r d o v i c i a n a n i m a l s d i r e c t l y from the m o r p h o l o g y o f shells

nia of the trilobite Isote-

a n d skeletons ( b o d y fossils) by c o m p a r i s o n s to their l i v i n g relatives, b u t a

lus,

Asaphoidichnus

vast r a n g e o f e v i d e n c e a b o u t a n c i e n t b e h a v i o r also c o m e s f r o m a c o m -

trifidum

Miller,

CMC IP

pletely different s o u r c e , n a m e l y the trace fossils that are b o t h a b u n d a n t a n d

37569,

Edenian,

Kope

diverse in C i n c i n n a t i a n strata. Trace fossils are e v i d e n c e o f t h e activities o f a n c i e n t o r g a n i s m s preserved in s e d i m e n t a r y rocks in t h e form of tracks, trails, b u r r o w s , b o r i n g s , a n d o t h e r fossils s u c h as

coprolites (fossil feces). M o s t t r a c e fossils w e r e

f o r m e d a s o r g a n i s m s d i s r u p t e d l o o s e s e d i m e n t s b e f o r e l i t h i f i c a t i o n , al-

A.

Formation,

Cincinnati,

Ohio, x 7.

B.

Repichnia

trilobite

Cryptoli-

of the thus,

similar to

ana,

CMC IP 37622,

zon

t h o u g h b o r i n g s are the results of d r i l l i n g , r a s p i n g , or e t c h i n g into h a r d

unknown, x 7. bite

Lebensspuren) has b e c o m e a s p e c i a l -

ized held o! g e o l o g y k n o w n as i e h n o l o g v . C i n c i n n a t i a n trace fossils with their exquisite preservation h a v e l o n g f a s c i n a t e d s t u d e n t s o f t h e s e r o c k s . A m o n g them were S. A. Miller, w h o described m a n y C i n c i n n a t i a n trace fossils b u t regarded t h e m t o b e the r e m a i n s o f m a r i n e p l a n t s ( s o - c a l l e d

trail,

lian,

Rusophycus Maysvil-

Clermont Co.,

Ohio

(from

Osgood [1970,

plate

66,

figure 3[), x 0.8. D.

O s g o o d , jr., w h o c o m p l e t e d his d o c t o r a l dissertation at t h e U n i v e r s i t y of

Edenian,

'Trace fossils greatly e n h a n c e the ability of the p a l e o n t o l o g i s t to r e c o n -

Trilo-


ictyon,

m e n t of m o d e r n i e h n o l o g v .

C.

Cruziana,

c o r r e c t o r g a n i c i n t e r p r e t a t i o n o f trace fossils ( O s g o o d 1975a). R i c h a r d C .

o f C i n c i n n a t i a n trace fossils a n d t h e r e b y c o n t r i b u t e d m u c h t o t h e d e v e l o p -

hori-

intermediate

between and

f u c o i d s ) , and J. F. James, w h o w a s o n e of t h e earliest p r o p o n e n t s of t h e

C i n c i n n a t i in 1905 ( O s g o o d 1970), c o n d u c t e d a t h o r o u g h s y s t e m a t i c r e v i e w

Cruzi-

and locality

substrata such as shells or a l r c a d v - l i t h i f i e d h a r d g r o u n d s . The study of trace fossils (also k n o w n as i c b n o f o s s i l s or

Repich-

Paschichnia, CMC IP

?Paleod17431,

Kope Forma-

tion, Cincinnati, Ohio, 3.

E.

x

Fodinichnia or

domichnia, track,"

the

"turkey

Trichophycus

venosum

Miller,

CMC IP

struct the life of the past i( )sgood 1975). In rare eases a trace fossil c a n be

37575,

preserved in close association with the b o d y fossil of the a c t u a l t r a c e i n a k e r

Kentucky,

( f i g u r e 14.2). U s u a l l y the identity of the t r a c e i n a k e r is u n k n o w n , often b e -

Osgood (1970,

c a u s e the traceinaker was soft-bodied and u n p r e s c r v a b l c . Different o r g a n -

figure 7). C, E reprinted

isms and different prcscrvational processes c a n s o m e t i m e s p r o d u c e a similar type of trace fossil. C o n s e q u e n t l y , trace fossils are not identified by a g e n u s and species n a m e of a b o d y fossil, but instead are g i v e n g e n u s and s p e c i e s

Campbell

Co.,

x 0.4. From plate

60,

by permission of the Paleontological Institution.

n a m e s of their o w n . The n e e d for this a p p r o a c h is further i n d i c a t e d b e c a u s e a single o r g a n i s m c a n p r o d u c e several different t y p e s of traces, d e p e n d i n g on its behavior. 'Thus, a one-for-onc c o r r e s p o n d e n c e b e t w e e n a t r a c e m a k i n g biological species a n d a given t y p e of trace fossil c a n n o t be establi s hed. T h e

203

Research

L i n n a e a n b i n o m i a l system w a s d e v e l o p e d for trace fossils b e c a u s e they were o n c e t h o u g h t t o b e b o d y fossils, and this p r o c e d u r e has persisted ( S i m p s o n 1975). Ideally, t h e i c h n o g e n u s m i g h t be d e f i n e d to represent a p a r t i c u l a r b e h a v i o r a l pattern w h i l e t h e i c h n o s p e c i e s represents variations on this patt e r n , a l t h o u g h this p r o c e d u r e has n o t b e e n u n i f o r m l y applied (Bromley 1990). T r a c e fossils p r o v i d e i n f o r m a t i o n a b o u t u n p r e s e r v a b l e soft part structures of a n i m a l s that are k n o w n as skeletal fossils. In the C i n c i n n a t i a n , g o o d e x a m p l e s of this are t h e varieties of Rusophycus, the resting trace of trilobites, w i t h i m p r e s s i o n s f o r m e d by t h e d i g g i n g activities of the legs ( F i g u r e 14.2A). T r a c e fossils also a u g m e n t o u r record of diversity by p r e s e r v i n g activities of entirely soft-bodied s p e c i e s that are o t h e r w i s e u n k n o w n in the record. T h e g r e a t e s t s i g n i f i c a n c e o f t r a c e fossils is, h o w e v e r , the i n f o r m a t i o n they yield about the behavior of long-dead animals.

The G e r m a n paleon-

tologist R u d o l f R i c h t e r p i o n e e r e d t h e a n a l y s i s o f a n c i e n t b e h a v i o r from t r a c e fossils b y s t u d y i n g t r a c e s m a d e b y shallow m a r i n e o r g a n i s m s i n R e c e n t s e d i m e n t s o f t h e N o r t h S e a . I n m a n y c a s e s m o d e r n tracks a n d trails c o u l d be c o m p a r e d to fossilized traces. A remarkable book by W i l h e l m S c h a f e r (1972) s u m m a r i z e s t h e w o r k o f R i c h t e r a n d m a n y s u b s e q u e n t G e r m a n s t u d e n t s o f t h e N o r t h S e a traces i n E n g l i s h . A d o l f S e i l a c h e r (1964) classified t r a c e fossils into b e h a v i o r a l c a t e g o r i e s that facilitated the interp r e t a t i o n o f a n c i e n t e n v i r o n m e n t s o n t h e basis o f trace fossil a s s e m b l a g e s .

Behavioral

R e p i c h n i a are t r a c e s m a d e b y t h e d i r e c t e d l o c o m o t i o n o f b e n t h i c o r g a n -

Categories of

i s m s . T h e s e are t h e m o s t c o m m o n t r a c e s i n t h e C i n c i n n a t i a n , w i t h s e v e n t e e n i c h n o s p e c i e s r e c o r d e d b y H o l l a n d (2005). T h e a p p e n d a g e s o f trilobites

Trace Fossils

o r o t h e r a r t h r o p o d s d i g g i n g into t h e s u b s t r a t u m d u r i n g c r a w l i n g f o r m e d several

repichnial

a n d Allocotkhnus trace

of t h e

t r a c e s . Asaphoidichnus

dyeri

trilobite

trifidum

M i l l e r r e p r e s e n t different lsotelus

(Osgood

1970).

(Miller) forms

(Figure

of the

Trachomatichnus

M i l l e r is t h e c r a w l i n g t r a c e of t h e trilobite Cryptolithus,

and

14.1A)

crawling numerosum Petaliclmus

multipartitum M i l l e r is t h e c r a w l i n g t r a c e of a m e d i u m - s i z e d , u n i d e n t i f i e d trilobite ( O s g o o d

1970). O t h e r c o m m o n r e p i c h n i a l

traces (Palaeophycus)

are t u b u l a r , u s u a l l y u n b r a n c h e d b u r r o w s that r u n slightly o b l i q u e t o b e d ding, preserved either as convex hyporeliefs or trough-like c o n c a v e epireliefs. (A h y p o r c l i c f is p r e s e r v e d on t h e b a s e or sole of a s e d i m e n t a r y b e d ; e p i r c l i e f s are p r e s e r v e d o n t h e u p p e r s u r f a c e o f a bed.) O s g o o d d e s c r i b e d t h r e e f o r m s o f Palaeophycus a n d i n d i c a t e d that m o d e r n c o u n t e r p a r t s are produced by infaunal burrowing of polychaete worms or molluscs. P a s c i c h n i a are m e a n d e r i n g traces m a d e b y the g r a z i n g activities o f d e posit feeders ( a n i m a l s that feed on p a r t i c u l a t e o r g a n i c matter either on or w i t h i n the b o t t o m s e d i m e n t ) . A l t h o u g h n o a c t u a l m e a n d e r i n g traces a r e f o u n d in t h e C i n c i n n a t i a n , o n e vcrv p e c u l i a r trace q u e s t i o n a b l y referred to Paleodictyon, is classified by O s g o o d as a p a s c i c h n i a ] trace ( F i g u r e 14.1D). T h i s trace is a r e m a r k a b l y r e g i d a r n e t w o r k of ridges as a c o n v e x hyporelief. It r e s e m b l e s the impression of a h o n e y c o m b or c h i c k e n wire. O s g o o d des c r i b e d o n l v t w o k n o w n s p e c i m e n s from t h e C i n c i n n a t i a n , and discussed the m a n y v a r y i n g interpretations that workers h a v e p r o p o s e d for the origin

204

A Sea without Fish

of Paleodictyon from o t h e r localities. A l t h o u g h it m a y be t h e i m p r e s s i o n of a patterned object b e i n g rolled a l o n g the s u b s t r a t u m , O s g o o d c o n c l u d e d that the C i n c i n n a t i a n Paleodictyon is a trace fossil. S e i l a c h e r (1977) interpreted patterned traces of this t y p e to represent c o m p l e x burrow systems rather than g r a z i n g patterns.

T h e s e b u r r o w n e t w o r k s are u s e d b y s o m e i n f a u n a l o r g a n -

isms for the " f a n n i n g " of m i c r o b e s b e n e a t h the sea floor. F o d i n i c l m i a are ( c e d i n g t r a c e s o f d e p o s i t f e e d e r s o p e r a t i n g f r o m a fixed b u r r o w . ies of the

The m o s t c o m m o n C i n c i n n a t i a n f o d i n i c h n i a are t h e variet-

b r a n c h i n g b u r r o w Chondrites as d e s c r i b e d

by O s g o o d .

Chon-

drites, t y p e - A a p p e a r i n g o n t h e v e r t i c a l e d g e s o f b e d s o f f i n e - g r a i n e d carb o n a t e s , r e s e m b l e s n a r r o w rootlets (0.8 m m a v e r a g e d i a m e t e r ) , s o m e t i m e s p e n e t r a t i n g t h e e n t i r e t h i c k n e s s o f a b e d (P'igure 14.3A). O n b e d d i n g p l a n e s , this form o c c u r s as a c i r c u l a r p a t t e r n of c l o s e l y s p a c e d h o l e s . Chondrites, t y p e - B c a n b e s e e n o n b o t h b e d d i n g p l a n e s a n d v e r t i c a l s e c t i o n s . C o m p a r e d t o Chondrites, t y p e - A , t y p e - B h a s t u b e s o f g r e a t e r d i a m e t e r ( 1 - 4 m m ) , a n d b r a n c h e s that p r o p a g a t e t o a g r e a t e r e x t e n t h o r i z o n t a l l y t h a n vertically ( F i g u r e 14.3B). Chondrites, t y p e - C o c c u r s a s d e n s e l y i n t e r w o v e n radiating branches, either parallel or oblique to b e d d i n g (Figure 14.3C). A n o t h e r c o m m o n a n d i n t e r e s t i n g C i n c i n n a t i a n t r a c e classified b y O s g o o d as f o d i n i c l m i a , or possibly d o m i c h n i a , is Trichophycus venosum M i l l e r ( F i g u r e 14.1F). The m o s t c o m m o n e x p r e s s i o n o f this t r a c e , f o u n d t h r o u g h out the C i n c i n n a t i a n , is a shallow elongate depression with r o u n d e d ends o n the u p p e r s u r f a c e o f calcisiltite b e d s . B e d s c o v e r e d w i t h t h e s e s c o o p - l i k e depressions, oriented in r a n d o m fashion, give the a p p e a r a n c e of overlapp i n g tracks o f large birds; h e n c e l o c a l c o l l e c t o r s refer t o t h e s e f e a t u r e s a s "turkey tracks." O s g o o d ' s c a r e f u l s t u d v o f " t u r k e v t r a c k s " r e v e a l e d that t h e y represent o n l y a part of a U - s h a p e d b u r r o w s t r u c t u r e w i t h b r a n c h e s in t h e vertical p l a n e . T h e d e p r e s s i o n s are often f i l l e d w i t h t h i n l a m e l l a e o f f i n e r g r a i n e d s e d i m e n t that i n d i c a t e t h e b u r r o w i n g o r g a n i s m d u g t h r o u g h a m u d layer until it r e a c h e d c o a r s e r silt, w h e r e u p o n it t u r n e d b a c k toward the s u r f a c e . A f t e r c o m p l e t i n g its d e e p e s t p e n e t r a t i o n t h e b u r r o w i n g o r g a n ism r e p o s i t i o n e d itself b y w o r k i n g u p w a r d , f o r m i n g t h e s t a c k e d l a m e l l a e and d i g g i n g new t u n n e l s u p w a r d , possibly r e a c h i n g t h e s u r f a c e . I n m o s t c a s e s s u b s e q u e n t e r o s i o n r e m o v e d t h e softer m u d , l e a v i n g t h e m o r e resistant silt w i t h o n l y the basal floor of the b u r r o w as t h e " t u r k e y track." by this i n t e r p r e t a t i o n , O s g o o d r e j e c t e d t h e f a s c i n a t i n g earlier idea p u t forth b y R o u s s e a u H . F l o w e r (1955) that " t u r k e y t r a c k s " r e p r e s e n t e d " t o u c h d o w n " i m p r e s s i o n s left b y n a u t i l o i d c e p h a l o p o d s . tracks" (width 2.5-3.5

c

m

The large size of the "turkey

) i n d i c a t e s t h e a c t i v i t y o f a l a r g e o r g a n i s m , b u t its

e x a c t identity r e m a i n s c o n j e c t u r a l . F i n e striations p a r a l l e l t o t h e l e n g t h o f the d e p r e s s i o n s w e r e f o r m e d b y a p p e n d a g e s o f a n a r t h r o p o d o r e h a e t a e o f a p o l y c h a e t e w o r m ( e h a e t a e are bristles e x t e n d i n g f r o m t h e b o d y s e g m e n t s o f a w o r m ) . B e c a u s e t h e b u r r o w s are n o t b i l o b e d , t h e y w e r e m o s t likelv n o t p r o d u c e d b y a trilobite w i t h p a i r e d a p p e n d a g e s . " T u r k e y t r a c k s " m a y w e l l represent the onlv e v i d e n c e we h a v e of a rather l a r g e , s o f t - b o d i e d i n f a u n a l o r g a n i s m that was q u i t e c o m m o n o n t h e C i n c i n n a t i a n sea f l o o r . D o m i c h n i a are p e r m a n e n t d w e l l i n g t r a c e s f o r m e d b y b e n t h i c a n i m a l s feeding by predation, scavenging, or suspension feeding.

The

"U-tube"

Type-Cincinnatian Trace Fossils

205

Diplocraterion i s t h e m o s t c o m m o n d o m i c h n i a l trace f o s s i l o f the C i n c i n n a t i a n . O s g o o d (1970) r e c o g n i z e d t h r e e i e l m o s p c c i e s o f Diplocraterion. A s s e e n on v e r t i c a l joint s u r f a c e s , / ) . cf. luniformis ( B l a n c k e n h o r n ) has a p l a i n I l-shape w i t h a r o u n d e d b a s e . N a r r o w , e l o n g a t e d slots on the u p p e r s u r f a c e of a b e d r e p r e s e n t t h e b a s e of t h e 11. In t h e m o r e c o m m o n / ) . cincinnatiensis ( O s g o o d ) t h e U e x p a n d s w i t h d e p t h in different w a y s ( f i g u r e s 14.3A, 14.4 \i. f a i n t dow n w a r d - c u r v i n g striations (Spreiten) c o n n e c t the a r m s of t h e U . T h e s e s o - c a l l e d p r o t r u s i v e Spreiten m a y represent the d o w n w a r d propagation of the burrow as the organism grew. Alternatively, the organism ma}' h a v e b u r r o w e d d e e p e r i n o r d e r t o m a i n t a i n a c o n s t a n t d e p t h b e low a constantly e r o d i n g sediment-water interface.

T h e reason for the basal

e x p a n s i o n i s u n c l e a r . S o m e e x p a n s i o n s o c c u r a t a n i n t e r f a c e with c o a r s e r m a t e r i a l , yet o t h e r s e x p a n d w i t h i n t h e silt-sized layer ( f i g u r e 14.4A). T h i s led O s g o o d (1970) to suggest that t h e o r g a n i s m may h a v e s e n s e d a c h e m i c a l c h a n g e i n t h e s e d i m e n t b e f o r e e n c o u n t e r i n g a c h a n g e i n g r a i n size. W e s p e c u l a t e that t h e e x p a n s i o n o f t h e U m i g h t h a v e d e v e l o p e d after t h e w o r m - l i k e o r g a n i s m b u r r o w e d t o its preferred d e p t h . Lateral e x p a n s i o n o f t h e U e n a b l e d t h e w o r m t o g r o w i n l e n g t h w h i l e m a i n t a i n i n g its d e p t h . T h e third Diplocraterion i c h n o s p e c i e s , D. biclavata ( M i l l e r ) , has a pair o f short e x t e n s i o n s d e v e l o p e d a t t h e b a s e o f t h e U a s b l i n d p o u c h e s . T h i s f o r m also o c c u r s a s c o n c a v e e p i r c l i e f s i n w h a t a r e c o m m o n l y c a l l e d " d u m b b e l l s " ( f i g u r e s 1 4 . 4 B , C ) . O s g o o d s h o w e d that d u m b b e l l s r e p r e s e n t the basal p e n e t r a t i o n o f t h e D - t u b e w i t h p a i r e d e x t e n s i o n s into a c o a r s e r s u b s t r a t u m t h a t u s u a l l y r e m a i n s after e r o s i o n s t r i p p e d off t h e u p p e r parts o f t h e U . A l l t h r e e i c h n o s p e c i e s o f Diplocraterion c a n b e f o u n d i n t h e s a m e b e d , s u g g e s t i n g t h a t a s i n g l e t y p e o f o r g a n i s m c o u l d h a v e p r o d u c e d all three expressions. T h e t r a c c m a k i n g organism was probablv some type of w o r m that u s e d t h e U - t u b e as its d w e l l i n g s t r u c t u r e , w h i l e s u s p e n s i o n feeding near the sediment-water interface. M a n y b o r i n g s found i n C i n c i n n a t i a n stromatoporoids, corals, b r y o z o a n s , b r a c h i o p o d s , m o l l u s c s , a n d h a r d g r o u n d s represent d o m i c h n i a . Pits on the u n d e r s i d e of a R i e h m o n d i a n stromatoporoid c o n t a i n the t r a c c m a k i n g bivalve Corallidomus scobina

Pojeta and

P a l m e r as t h e oldest-known c a s e of hard

substrate b o r i n g by a p e l e c y p o d (see F i g u r e 9.8A; Pojeta and P a l m e r 1976). T h e s a m e e l o n g a t e pits, now referred to the i c h n o s p e c i e s Petroxestes pera, are also f o u n d in c a l c a r e o u s n o d u l e s a n d the bases of b r y o z o a n s ( W i l s o n and P a l m e r 1988). C i n c i n n a t i a n r u g o s e corals of the g e n u s Grewiugkia c o m m o n l y show b o r i n g s c a l l e d Trypanites (see f i g u r e 6.5K; f l i a s 1986). A l t h o u g h it is usually impossible to d e t e r m i n e w h e t h e r the b o r i n g s o c c u r r e d d u r i n g the life of the c o r a l , Klias f o u n d s o m e b o r i n g s e n c a s e d w i t h i n swellings of the coral septa. F l i a s inferred that a b o r i n g w o r m penetrated the septa of a living coral, resulting in the secretion of the septal s w e l l i n g . In other eases borings did not c o m e into c o n t a c t with the living coral polyps, hut were probablv located on corals in life position so as to e x p o s e the w o r m s to a m b i e n t c u r r e n t flow. A distinctive t y p e of b o r i n g c a l l e d Sanctum laurentiensis

f rickson and

B o u c h a r d o c c u r s a s isolated, r o u n d t u n n e l s o n t h e interior o f b r a n c h i n g C i n c i n n a t i a n b r y o z o a n s ( K r i c k s o n and B o u c h a r d 2003). T h e interior o f the excavation is e l o n g a t e or sack-shaped and 1 m i m e d . T h e trace-maker was likely

206

A Sea without Fish

Figure 1 4 . 2 . nia

A.

and sderite

sions

of

trilobite

Rusophycus James),

Isotelus,

carleyi (J.

F.

CMC IP 46411,

Maysvillian,

Corryville

Formation,

Clermont

Ohio,

x 0.6.

sions

of cephalic

margin,

pleurae,

pygidial margin, coxae

Co.,

Note impres-

genal spines, as

Cubich-

impres-

as well

(medial paired

lobes,

flanked by cres-

centic

impressions

made

by legs. Also, at top, note Paleophycus terminating mate

burrow at

approxi-

position

of trilobite

mouth,

with

posed

scratchmarks.

superim-

B.

Flexicalymene

meeki

(Foerste),

37574,

CMC IP

Maysvillian,

ryville Formation, mont Co., 1.4.

Ohio,

Right:

x

Reverse side

of specimen shown cubichnia

CorCler-

in

pudicum

Hall,

convex

hyporelief,

identifying

trilobite

tracemaker.

This

as

exceptional

speci-

men is one of the very few known

with

trace

tracemaker

and

preserved

Type-Cinannatian Trace Fossils

207

B,

Rusophycus

both

together.

Figure

14.3.

Diplocraterion

A.

Kope Formation,

Osgood;

Cincinnati, Ohio,

Corryville Formation, mondian,

Vertical joint surface showing two commonly associated trace fossils: at left,

cincinnatiensis

x

at right, 1.3.

Clermont Co., Ohio,

Whitewater Formation,

forme (Miller and Dyer),

B. x 0.9.

Wayne Co.,

CMC IP uncatalogued,

208

fodinichnia, Fodinichnia, C.

Indiana,

1.2.

type-A,

Chondrites, type-B,

Fodinichnia, x

Maysvillian,

A Sea without Fish

Chondrites,

D.

domichnia,

CMC IP 37607,

Edenian,

CMC IP 37623, Maysvillian,

Chondrites, type-C,

CMC IP 37678, Rich-

Cubichnia of sea star, Asteriacites stelli-

PCorryville Formation,

Cincinnati,

Ohio,

x

7.

Figure

14.4.

A.

uncatalogued, rion

Vertical joint surface showing domichnia,

Edenian,

biclavata

Kope Formation,

(Miller),

showing

Campbell Co.,

U-tube and spreiten

Diplocraterion

Kentucky,

x 0.8.

constructed in

from Osgood (1970). IP 37657, Maysvillian, 0.4.

D.

C.

the upper surface of the calcisiltite,

Domichnia Diplocraterion biclavata

Corryville Formation, Clermont Co., Ohio,

bioimmuration structure in bryozoan,

Catellocaula vallata Palmer and Wilson, x.2.3.

E.

cypods, Lockeia siliquaria U. P. James, CMC IP 37597, Edenian, Kenton Co., Kentucky, holotype,

originally interpreted as (1970) to be either a tube,

x 0.6.

B,

CMC IP 24079, the impression

Maysvillian,


of a porpitid jellyfish,

this impression

base a

Modified

"dumbbell" on upper surface,

(from Osgood [1970, plate 61,

nati collection, Edenian, Point Pleasant Formation, Bracken Co., Kentucky, floweri Caster,

with

When shale is eroded away,

as shown in lower diagram.

(Miller),

CMC IP,

Reconstruction of Diplocrate-

upper shale (dashed pattern)

of U and paired lateral extensions in underlying calcisiltite (stippled pattern). "dumbbell" impression remains on

cincinnatiensis Osgood, B.

figure 3]),

CMC x

University of Cincin-

Cubichnia of pelex 0.5.

Clermont Co.,

F.

Palaeoscia

Ohio. Although

was considered by Osgood

feeding trace or of inorganic origin as a result of rotatory sweeping of an agglutinated

C reprinted by permission of the Paleontological Research Institution.


209

a c r u s t a c e a n that took a d v a n t a g e of the b r y o z o a n host for protection as well as for an elevated f e e d i n g position. E x c a v a t i o n of the interior of the b r v o z o a n b r a n c h e s probably r e d u c e d the structural integrity of the colonv and rendered it m o r e susceptible to b r e a k a g e d u r i n g storms. Trypanites borings on b r y o z o ans u s u a l l y o c c u r in clusters and w e r e probably f o r m e d w h e n d e a d , broken c o l o n i e s w e r e e x p o s e d on the sea floor ( E r i c k s o n and B o u c h a r d 2003). A n o t h e r type of trace found in C i n c i n n a t i a n brvozoan colonies is not a c t u a l l y a b o r i n g b u t rather r e c o r d s t h e p r e s e n c e of a s o f t - b o d i e d o r g a n i s m that lived a s a n e n d o s y m b i o n t w i t h i n t h e b r v o z o a n s k e l e t o n , t e r m e d b i o c l a u s t r a t i o n b y P a l m e r a n d W i l s o n (lcjHS) ( f i g u r e 1 4 . 4 0 ; s e e F i g u r e 11.6E). A f t e r s e t t l e m e n t by a larva of t h e e n d o s y m b i o n t o n t o the l i v i n g colonv, b r v o z o a n z o o e c i a grew a r o u n d the o r g a n i s m In c o n f o r m a t i o n to its s h a p e , r e s u l t i n g in d i s t i n c t i v e pits a r r a n g e d in r o w s , n a m e d Catellocaula vallata by P a l m e r a n d W i l s o n (19S8). t i n l i k e b o r i n g s , the m a r g i n of t h e s e pits is l i n e d b y z o o e c i a l w a l l s . T h e m o r p h o l o g y o f the pits and their a r r a n g e m e n t in rows s u g g e s t e d a c o l o n i a l , s t o l o n i f e r o u s o r g a n i s m , m o s t likely a t u n i c a t e . T a p a n i l a (2005) has p r o p o s e d that a new b e h a v i o r a l c a t e g o r y , I m p e d i c h n i a , b e u s e d for s u c h c a v i t i e s that l o c a l l y i n h i b i t the n o r m a l skeletal g r o w t h o f t h e host. Catellocaula vallata r e p r e s e n t s o n e of the oldest k n o w n e x a m p l e s o f this e n d o s y m b i o t i c b e h a v i o r . C u b i c h n i a are t e m p o r a r y traces m a d e b y m o b i l e a n i m a l s . A l t h o u g h they are often regarded as " r e s t i n g " traces, there is also the possibly that s o m e c u b i c h n i a represent f e e d i n g or predation b u r r o w s . Trilobite "resting" traces, represented by three i c h n o s p e c i e s of Rusophycus, are a m o n g the m o s t c o m m o n c u b i e h n i a l traces in the C i n c i n n a t i a n . O s g o o d (1970) r e c o g n i z e d R. pudicum I lall as the trace of Flexicalymene on the basis of its size and a few e x c e p t i o n a l o c c u r r e n c e s of the t r a c c n i a k e r preserved with the trace directly b e n e a t h it ( f i g u r e 14.2B). O c c a s i o n a l l y clusters of R. pudicum are found that suggest the activity of several trilobites, a l t h o u g h a single individual c o u l d also p r o d u c e m u l t i p l e b u r r o w s in close proximity. R. carleyi O. f. James) is a large b u r r o w attributable to the largest C i n c i n n a t i a n trilobite Isotelus. In a few exc e p t i o n a l s p e c i m e n s , casts of the c e p h a l i c and pvgidial m a r g i n , genal spines, and p l e u r a e are present a l o n g with impressions formed by the w a l k i n g legs ( f i g u r e 14.2A; O s g o o d 1970; Brandt et al. 1995). hi e v e n rarer s p e c i m e n s , intersection by the trilobite trace of a w o r m burrow suggests that the burrow was f o r m e d for the p u r p o s e s of predation ( F i g u r e 14.2A; Brandt et al. 1995; Fortey a n d O w e n s 1999). S m a l l , ovoid Rusophycus (R. cryptolithi) are consistent with formation by the trilobite Cryptolithus ( O s g o o d 1970). O t h e r c u b i e h n i a l traces for w h i c h the t r a c c n i a k e r is identifiable are Lockeia siliquaria U. P. James, f o r m e d by shallow-burrow i n g p e l e c v p o d s ( f i g u r e 14.4F) and Asteriacites stelliforme ( M i l l e r a n d O v e r ) f o r m e d by sea stars ( F i g u r e 14.3D; O s g o o d 1970).

Ichnofacies and

S e i l a c h e r (1964) p r o p o s e d that t h e relative a b u n d a n c e of trace fossils b e l o n g -

Paleoenvironmental

i n g to the b e h a v i o r a l c a t e g o r i e s varied a c c o r d i n g to the s u b m a r i n e e n v i r o n m e n t , c h i e f l y in relation to d e p t h .

Interpretation

Trace fossil a s s e m b l a g e s ( i c h n o f a c i e s )

d o m i n a t e d b y d o m i c h n i a ] and c u b i e h n i a l traces c h a r a c t e r i z e shallow, nearshore m a r i n e e n v i r o n m e n t s b e c a u s e c o n d i t i o n s o f h i g h t u r b u l e n c e c a u s e

210

A Sea without Fish

vagile o r g a n i s m s and s u s p e n s i o n feeders to seek shelter in b u r r o w s . As d e p t h increases w i t h i n the shallow n e a i shore / o n e , c o n d i t i o n s of l o w e r water m o v e m e n t p e r m i t food p a r t i c l e s to settle, a n d thus deposit f e e d i n g activity increases, resulting in f o d i n i e h n i a l traces. In d e e p sea e n v i r o n m e n t s t h e r e is little n e e d for p e r m a n e n t shelter, and so d w e l l i n g a n d resting traces are n o t f o r m e d ; instead, o r g a n i s m s tend to g r a z e the s e d i m e n t s u r f a c e for f o o d , creating the m e a n d e r i n g p a s c i c h n i a l traces. K e p i c l m i a l traces are f o u n d in all s u b m a r i n e e n v i r o n m e n t s , b e c a u s e o r g a n i s m s are a l w a y s g o i n g s o m e w h e r e a n d l e a v i n g trails, n o matter w h a t the setting! S e i l a c h e r ' s o r i g i n a l c o n c e p t o f trace fossil facics distribution has b e e n w i d e l y tested, s u b s t a n t i a t e d , and expanded to include assemblages characterizing non-marine environments and p a r t i c u l a r substrata s u c h a s h a r d g r o u n d s a n d w o o d ( B r o m l e y 1990). C a n t h e i c h n o f a c i e s c o n c e p t b e a p p l i e d t o C i n c i n n a t i a n trace f o s s i l s , a n d what c a n this tell us a b o u t the Late O r d o v i c i a n m a r i n e e n v i r o n m e n t ? O s g o o d (1970) listed thirty i c h n o g e n e r a a n d forty-four i c h n o s p e c i e s from t h e C i n c i n n a t i a n . R e c e n t a d d i t i o n s a n d revisions b r i n g t h e total t o thirty-four i c h n o g e n e r a and fortv-seven i c h n o s p e c i e s ( H o l l a n d 2005; T a p a nila 200^). The f o l l o w i n g list s h o w s the distribution of t h e s e i c h n o s p e c i e s . Cubichnia Domichnia Repichnia

5 6 17

Kodinichnia

9

Pascichnia

1

[mpedichnia

2

Borings

2

incertae sedis

5

T h e h i g h diversity i n the c a t e g o r i e s d o m i c h n i a , c u b i c h n i a , a n d fod i n i c h n i a , c o m p a r e d t o the s i n g l e (and rare) o c c u r r e n c e o f p a s c i c h n i a , led S e i l a c h e r (1964) a n d O s g o o d (1970) to c o n c l u d e that the C i n c i n n a t i a n as a w h o l e c o i n c i d e s w ith the Cruziana i c h n o f a c i e s , r e f l e c t i n g a s h a l l o w , o p e n m a r i n e e n v i r o n m e n t . O s g o o d s u g g e s t e d that the C i n c i n n a t i a n m a r i n e e n v i r o n m e n t w a s m i d e e p e r M i a n about 35 i n . V e r y little work has b e e n d o n e t o refine p a l e o e n v i r o n m e n t a l a n a l y s i s o f the C i n c i n n a t i a n u s i n g trace f o s s i l s . O s g o o d n o t e d that a " s u b a s s o c i a t i o n " of three trace

fossils,

Diplocraterion,

Chondrites,

a n d Trichophycus is

found in s i n g l e b e d s n e a r the top of t h e K o p c F o r m a t i o n a n d r e c u r s in the C o r r y v i l l e a n d a g a i n in the Liberty F o r m a t i o n s , s u g g e s t i n g a r e c u r r e n c e of s i m i l a r c o n d i t i o n s . I l i g h r e s o l u t i o n s t r a t i g r a p h i c w o r k has d e m o n s t r a t e d that t h e s e Diplocraterion b e d s in t h e u p p e r K o p c are w i d e l v t r a c e a b l e o v e r the G r e a t e r C i n c i n n a t i r e g i o n ( J e n n e t t e a n d P r y o r 1993; Brett e t a l . 2001b), but there has b e e n no d e t a i l e d study of t h e trace fossil a s s o c i a t i o n .

"Traces" of Inorganic or Indeterminate Origin S e v e r a l s e d i m e n t a r y s t r u c t u r e s i n C i n c i n n a t i a n strata w e r e n a m e d a s " f u c o i d s " but are likely t o h a v e a n i n o r g a n i c o r i g i n o r r e m a i n p r o b l e m a t i c .


211

T h e s e are u s u a l l y p r e s e r v e d a s h y p o r e l i e f s . O n e s u c h s t r u c t u r e , "Blastophycus," p r o b a b l y r e p r e s e n t s c a s t i n g s of i m p r e s s i o n s left by e n r o l l e d trilobites a n d c u r r e n t s c o u r a r o u n d t h e m ( O s g o o d 1970). A n o t h e r , "Dystactophycus," i s a f a n - s h a p e d p a t t e r n o f f i n e c o n c e n t r i c ridges a n d g r o o v e s , a n d w a s o n c e t h o u g h t t o b e a n a l g a l f r o n d . O s g o o d c o n c l u d e d that i t f o r m e d b y rotation of a c r i n o i d s t e m as it w a s b u r i e d . At several C i n c i n n a t i a n l o c a l i t i e s , perfectly circular impressions of c o n c e n t r i c rings o c c u r on the upper surface o f a b e d ( F i g u r e 1 4 . 4 F ) . C a s t e r i n t e r p r e t e d t h e s e t o b e b o d y fossil m o l d s o f a p o r p i t i d jellyfish a n d d e s c r i b e d t h e m as Palaeoscia floweri (see C a s t e r 1942). H o w e v e r , O s g o o d e x a m i n e d a d d i t i o n a l s p e c i m e n s a n d c o n s i d e r e d t h a t t h e s e c o n c e n t r i c r i n g s c o u l d h a v e f o r m e d u n d e r t h e i n f l u e n c e o f currents b y r o t a t i o n a l s w e e p i n g o f s o m e k i n d o f o r g a n i c d w e l l i n g t u b e e m b e d d e d i n t h e s e d i m e n t . A l t e r n a t i v e l y , s o m e l i v i n g p o l y c h a e t e s create a f e e d i n g t r a c e t h a t r e s e m b l e s Palaeoscia, a n d t h u s O s g o o d

relegated

these most

p e c u l i a r C i n c i n n a t i a n " t r a c e s " to incertae sedis. S t a n l e y (1986) s u p p o r t e d O s g o o d ' s a s s e s s m e n t t h a t Palaeoscia is a t r a c e fossil, b u t c o n t r o v e r s y c o n t i n u e s o v e r i n t e r p r e t a t i o n of Palaeoscia a n d s i m i l a r c o n c e n t r i c ring-like s t r u c t u r e s i n t h e g e o l o g i c a l r e c o r d ( E w i n g a n d D a v i s 1967, 274-275). B e l l et al. (2001) listed C i n c i n n a t i a n Palaeoscia as a jellyfish, a n d asserted that O s g o o d w a s i n c o r r e c t in r e g a r d i n g it as a t r a c e fossil, b u t g a v e no basis for this e v a l u a t i o n .

212

A Sea without Fish

Figure 15.1. Divisions of type-Cincinnatian Geologists tionally

strata.

have

tradi-

defined

sedimen-

tary rocks on the basis of time,

usually inferred

from

fossil

and on type.

assemblages,

the basis of rock The

has

Cincinnatian

been

traditionally

divided into

three stages,

shown at the far left,

and

there is currently disagreement tive

over

the

durations

three stages. stage,

rela-

of these A

fourth

indicated by

and called the chian Stage, ent in

"G"

Gama-

is not pres-

the Cincinnati area.

The divisions based on rock type are shown at the right.

Most of those

in modern shown, different have

usage are

but dozens of named

been

divisions

proposed

over

the years and are not shown.

The names cur-

rently used by the and

Kentucky

surveys differ, dashed cate

Ohio

geological and

vertical lines

these

indi-

"stateline

stratigraphic

divisions."

The

Geological

Indiana

Survey

recognizes

Kope,

Whitewater,

Saluda

Formations,

assigns

all strata

the

Kope and

the and and between

Whitewa-

ter to the Bull Fork Formation

(not shown).

Type-Cincinnatian have also

been

strata divided

into six units that reflect cycles

of

sedimentation

produced by

the rise and

fall of sea level. depositional numbered bounded

These sequences,

C1-C6, by

reflect falls in sea level that drained the seas from the Cincinnati area, ing in

no deposition

ties is poorly known.

are

unconformi-

ties shown in gray that

214

A Sea without Fish

of sediments.

The actual duration

of these

result-

unconformi-

15

PALEOGEOGRAPHY AND PALEOENVIRONMENT Steven M. Holland

E a r t h scientists r e c o n s t r u c l c o n d i t i o n s d u r i n g t h e a n c i e n t past f r o m a w i d e variety o f c h i c s from m i n e r a l s , r o c k s , a n d f o s s i l s . A l t h o u g h n o p l a c e o n E a r t h today i s e x a c t l y like t h e C i n c i n n a t i area d u r i n g t h e L a t e O r d o v i c i a n , c o m p a r i s o n s w i t h m o d e r n e n v i r o n m e n t s offer v a l u a b l e i n s i g h t s into t h e interpretation o f t h e s e c l u e s . O f m o d e r n e n v i r o n m e n t s , t h e Persian G u l f is perhaps the most similar to the Late O r d o v i c i a n of the eastern United States in t e r m s of its c l i m a t e , t h e s i z e of the s e d i m e n t a r y b a s i n , the gcntlv d i p p i n g sea floor, t h e m i x o f c a r b o n a t e s e d i m e n t a n d clay, a n d t h e o c c u r r e n c e o f storms that rework a n d d e p o s i t s e d i m e n t .

" W h e n Cincinnati Was in the Southern H e m i s p h e r e "

Geography

( T i t l e of a p r e s e n t a t i o n by K e n n e t h E, C a s t e r for t h e C i n c i n n a t i Historical S o c i e t y , 1974) G l o b a l g e o g r a p h y d u r i n g the O r d o v ician has b e e n r e c o n s t r u c t e d primarily t h r o u g h s t u d i e s o f the m a g n e t i c p r o p e r t i e s o f O r d o v i c i a n r o c k s . \ \ h e n s e d i m e n t s a r e d e p o s i t e d , i r o n - b e a r i n g m i n e r a l s t e n d t o a l i g n w i t h the Earth's m a g n e t i c f i e l d . A s the s e d i m e n t s b e c o m e c e m e n t e d t o g e t h e r a n d u n d e r g o lithifieation t o b e c o m e r o c k s , t h e s e m i n i a t u r e m a g n e t s are l o c k e d in place. By careful m e a s u r e m e n t of the orientations of these iron-bearing m i n e r a l s , g e o p h y s i c i s t s r e c o n s t r u c t the l a t i t u d e a t w h i c h t h e s e d i m e n t s were originally deposited. Four large continents d o m i n a t e d the globe d u r i n g the O r d o v i c i a n (Plate 1). S t r e t c h i n g from the S o u t h Pole into t h e n o r t h e r n h e m i s p h e r e , Gondvv ana w a s t h e largest o f t h e s e c o n t i n e n t s a n d c o n s i s t e d o f m o d e r n dav S o u t h A m e r i c a , A f r i c a , A r a b i a , A n t a r c t i c a , A u s t r a l i a , India, s o u t h e a s t Asia, a n d parts o f C h i n a . L a u r e n t i a i n c l u d e d m o s t o f p r e s e n t - d a y N o r t h A m e r ica, e x c e p t for New E n g l a n d a n d M a r i t i m e ( ' a n a d a , parts o f t h e s o u t h e a s t ern U n i t e d States, a n d t h e west c o a s t o f t h e U n i t e d States a n d C a n a d a , all of which were added to Laurentia d u r i n g subsequent tectonic collisions. L a u r e n t i a straddled t h e e q u a t o r d u r i n g the O r d o v i c i a n a n d w a s rotated 45" c l o c k w i s e from its present-day o r i e n t a t i o n . As a result, C i n c i n n a t i w a s situated a t 20-25° s o u t h o f t h e e q u a t o r for t h e e n t i r e L a t e O r d o v i c i a n . T o t h e east o f L a u r e n t i a a l o n g the e q u a t o r sat t h e c o n t i n e n t o f S i b e r i a - K a z a k h s t a n , w h i c h consisted o f present-day p o r t i o n s o f c e n t r a l A s i a . T h e f o u r t h c o n t i n e n t , B a l t i c a , lav to the s o u t h at r o u g h l y 60° a n d w a s c o m p o s e d of n o r t h e r n Europe and Scandinavia.

215

T h r e e major o c e a n s separated these continents. T h e I a p e t u s O c e a n separated L a u r e n t i a and S i b e r i a - K a z a k h s t a n from B a l t i c a t o the s o u t h . T h e P a l e o t e t h y s O c e a n lay b e t w e e n G o n d w a n a a n d t h e c o n t i n e n t s o f B a l t i c a a n d S i b e r i a - K a z a k h s t a n t o t h e w e s t . T h e m a s s i v e P a n t h a l a s s i c O c e a n cove r e d a l m o s t all o f t h e N o r t h e r n H e m i s p h e r e a n d w o u l d have d w a r f e d today's Pacific O c e a n . G l o b a l sea level w a s h i g h d u r i n g the O r d o v i c i a n , and a l t h o u g h its p o s i t i o n is d i f f i c u l t to c o n s t r a i n , t h e c u r r e n t c o n s e n s u s is that it was 100 to 200 m e t e r s h i g h e r t h a n p r e s e n t - d a y sea level (see F i g u r e 1.3). S e v e r a l factors c o n t r i b u t e d to s u c h a h i g h p o s i t i o n of sea l e v e l . Rates of sea floor s p r e a d i n g w e r e h i g h f o l l o w i n g t h e b r e a k u p o f a n older, L a t e P r o t e r o z o i c s u p e r c o n t i n e n t c a l l e d R o d i n i a , c a u s i n g t h e a v e r a g e e l e v a t i o n o f the sea floor t o b e higher than normal.

This r a i s i n g o f t h e " b o t t o m o f the b u c k e t " forced

o c e a n waters to spill o n t o t h e c o n t i n e n t s . In a d d i t i o n , the lack of p o l a r ice c a p s in m o s t of t h e O r d o v i c i a n a l s o w o u l d h a v e raised sea level relative to t o d a y b e c a u s e w a t e r i n m o d e r n g l a c i a l ice c a p s s u c h a s A n t a r c t i c a a n d G r e e n l a n d is p r o d u c e d from snow generated by evaporation from the o c e a n . B e c a u s e o f this h i g h sea l e v e l , l o w - l y i n g areas o n the c o n t i n e n t s w e r e f l o o d e d w i t h o c e a n w a t e r s , m u c h like the f l o o d i n g o f the present-day c o n t i n e n t a l s h e l v e s , b u t t o a m u c h greater e x t e n t . D u r i n g m u c h o f the O r d o v i c i a n , most o f L a m e n t i a w a s s u b m e r g e d , w i t h the e x c e p t i o n o f parts o f t h e C a n a d i a n S h i e l d , a low m o u n t a i n r a n g e r u n n i n g from M i n n e s o t a toward C o l o r a d o , t h e O z a r k r e g i o n o f M i s s o u r i , a n d the u p l i f t i n g l a c o n i c M o u n t a i n s a l o n g t h e s o u t h e a s t e r n e d g e o f L a u r e n t i a (Plate 1). The eastern U n i t e d States was d i v i d e d into several g e o g r a p h i c regions d u r i n g t h e L a t e O r d o v i c i a n (Plate 12). E x t e n d i n g from central K e n t u c k y n o r t h w a r d into O h i o a n d I n d i a n a w a s a shallow

m a r i n e c a r b o n a t e area

k n o w n a s the L e x i n g t o n Platform. W a t e r d e p t h s o n the L e x i n g t o n Platform d e e p e n e d t o the n o r t h . T h e L e x i n g t o n Platform was b o u n d e d o n the west by a d e e p e r water t r o u g h k n o w n as the S e b r e e T r o u g h . Far to the east rose t h e T a c o n i c M o u n t a i n s , p r o d u c e d by the collision of Laurentia with a small plate or island are, s u c h as the m o d e r n - d a y islands of Japan and the A l e u tians. This c o l l i s i o n w a r p e d t h e s o u t h e a s t e r n m a r g i n of L a u r e n t i a to form a d e e p water trough c a l l e d the A p p a l a c h i a n Basin that separated the l a c o n i c M o u n t a i n s from the L e x i n g t o n Platform. Into this t r o u g h , s e d i m e n t s shed from the e r o d i n g T a c o n i c M o u n t a i n s built a Series of northwest ward-advanci n g deltas c a l l e d the Q u e e n s t o n D e l t a . " R e d - b e d " tidal f l a t s e d i m e n t s typical of the Q u e e n s t o n c a n be seen in the latest O r d o v i c i a n strata on the eastern side o f t h e C i n c i n n a t i A r c h i n A d a m s C o u n t y , O h i o .

Climate

The c l i m a t e o f t h e L a t e O r d o v i c i a n was w a r m , with m u c h m o r e e v e n t e m peratures from the p o l e to the e q u a t o r than seen today. H i g h c o n c e n t r a t i o n s of c a r b o n d i o x i d e in t h e a t m o s p h e r e (referred to as the partial pressure of carbon dioxide, or pCO2,) caused these w a r m conditions. C o m p u t e r models and l i m i t e d g e o c h e m i c a l data from O r d o v i c i a n soil deposits suggest that levels of a t m o s p h e r i c pCO2, w e r e nearly sixteen times greater than today, c o m pared to the 20 p e r c e n t i n c r e a s e in pCO2,witnessed in the past half-century.

216

A Sea without Fish

W a r m t e m p e r a t u r e s a t the p o l e s i n h i b i t e d t h e f o r m a t i o n o f i c e c a p s , s u c h a s today's c o n t i n e n t a l g l a c i e r s o n A n t a r c t i c a a n d G r e e n l a n d a n d the sea ice o v e r the A r c t i c O c e a n . I n t h e last m i l l i o n years o f the O r d o v i c i a n , a t m o s p h e r i c p C O , levels d r o p p e d precipitously, t r i g g e r i n g t h e rapid g r o w t h 2

of p o l a r g l a c i e r s a n d a g e o l o g i c a l l y brief 160 m e t e r g l o b a l sea level fall. T h i s fall in sea level d r a i n e d t h e seas f r o m t h e C i n c i n n a t i a r e a , p r o d u c i n g an e r o s i o n a l division b e t w e e n t h e O r d o v i c i a n a n d S i l u r i a n strata c a l l e d a n unconformity. In a d d i t i o n to this e n d - O r d o v i c i a n fall in sea l e v e l , e v i d e n c e for six c y c l e s o f g l o b a l sea level c h a n g e i s p r e s e r v e d i n the O r d o v i c i a n n e a r C i n c i n n a t i ( f i g u r e 15.1). T h e e v i d e n c e for t h e s e c y c l e s c o m e s f r o m p a c k a g e s o f rock k n o w n a s d e p o s i t i o n a l s e q u e n c e s , w h i c h are b o u n d e d b y u n c o n f o r m i t i e s , o r s u r f a c e s that record t h e e r o s i o n a n d w e a t h e r i n g o f s e d i m e n t s . E a c h d e p o s i t i o n a l s e q u e n c e b e g i n s w i t h a relatively t h i n interval o f r o c k that records l o c a l d e e p e n i n g o f t h e o c e a n s a n d e n d s w i t h a m u c h t h i c k e r interval o f rock that r e c o r d s p r o g r e s s i v e s h a l l o w i n g o f t h e o c e a n s . T h e s e s a m e s e q u e n c e s c a n b e r e c o g n i z e d across the U n i t e d States a n d i n E s t o n i a . The fact that t h e s e s e q u e n c e s are n o t just l o c a l f e a t u r e s is s t r o n g e v i d e n c e that they reflect g l o b a l sea level c h a n g e s rather t h a n l o c a l t e c t o n i c c h a n g e s . I n t h e C i n c i n n a t i a r e a , t h e s e si\ d e p o s i t i o n a l s e q u e n c e s a l s o c o n t a i n e v i d e n c e of shorter-term v a r i a t i o n s in sea l e v e l , but it is c u r r e n t l y u n c l e a r w h e t h e r t h e s e represent g l o b a l o r r e g i o n a l c h a n g e s i n sea l e v e l . f r o m s t u d i e s o f t o d a y s g e o g r a p h y a n d c l i m a t e , a s well a s d i r e c t e v i d e n c e from O r d o v i c i a n strata, g e o l o g i s t s h a v e r e c o n s t r u c t e d t h e O r d o v i c i a n c l i m a t e o f the C i n c i n n a t i area.

Today, r e g i o n s n e a r 30° n o r t h a n d

south of the e q u a t o r are c h a r a c t e r i z e d by d e s e r t s , w h i c h f o r m as air r i s i n g n e a r the e q u a t o r d e s c e n d s a n d f o r m s a series of h i g h p r e s s u r e c e l l s that inhibit rainfall. I n O r d o v i c i a n rocks o f the C i n c i n n a t i a r e a , d i r e c t e v i d e n c e of such a semi-arid climate can be seen in the finely l a m i n a t e d d o l o m i t i c tidal flat deposits of c e n t r a l K e n t u c k y . S i m i l a r d e p o s i t s o c c u r in s e m i - a r i d regions today, w h e r e h i g h tides d e p o s i t t h i n l a m i n a e o f s e d i m e n t , b u t h i g h salinity a n d t e m p e r a t u r e e x c l u d e a n i m a l s that m i g h t burrow a n d d i s r u p t the s e d i m e n t . D o l o m i t e itself c a n h a v e a variety of o r i g i n s , b u t the t e x t u r e and o c c u r r e n c e o f d o l o m i t e i n C i n c i n n a t i a n r o c k s m a t c h e s that f o u n d i n m o d e r n s e m i - a r i d s e t t i n g s w i t h h i g h rates o f e v a p o r a t i o n .

Trade w i n d s

c h a r a c t e r i s t i c o f s u b t r o p i c a l l a t i t u d e s w o u l d h a v e b l o w n w e s t w a r d across the C i n c i n n a t i area d u r i n g t h e O r d o v i c i a n . The C i n c i n n a t i area w a s s u b j e c t e d t o f r e q u e n t h u r r i c a n e s , w h i c h p r o d u c e d the d i s t i n c t i v e a l t e r n a t i o n s o f l i m e s t o n e a n d m u d s t o n e , often c a l l e d s h a l e , a l t h o u g h few true s h a l e s exist in t h e C i n c i n n a t i area ( F i g u r e 15.2; see f i g u r e 4.6). A l t h o u g h there is c o n s i d e r a b l e v a r i a t i o n in i n d i v i d u a l s t o r m deposits as a result of d i f f e r e n c e s in s e d i m e n t supply, w a t e r d e p t h , p r o x i m ity t o t h e h u r r i c a n e , a n d the s t r e n g t h o f t h e h u r r i c a n e , m o s t o f t h e s e d e posits c o n t a i n a t least s o m e o f t h e c h a r a c t e r i s t i c f e a t u r e s p r o d u c e d b y storms. S t o r m - g e n e r a t e d

deposits

are well k n o w n not o n l y from s e d i m e n t

cores on m o d e r n continental shelves, but also t h r o u g h o u t the geologic record. S t o r m b e d s t y p i c a l l y h a v e a n e r o s i o n a l b a s e , w h i c h reflects p r o g r e s sively i n t e n s i f y i n g c u r r e n t s a n d w a v e s as the storm a p p r o a c h e s .

This e r o -

Paleogeography and Paleoenvironment

217

Figure of

15.2.

benthic

by

Destruction communities

storm-generated

waves and currents.

Dur-

ing calm,

con-

pre-storm

ditions,

benthic

nities

commu-

of organisms

develop on Under

the sea

storm

high

winds

floor.

conditions, generate

large waves that stir up fine-grained iments

bottom

into

sed-

S T A G E III. C A L M C O N D I T I O N S , P O S T - S T O R M

suspension.

Stronger wave and current forces can benthic

suspended clog

displace

organisms,

and

sediment

feeding

can

and respira-

tory mechanisms

of or-

ganisms,

and even

smother

entire

benthic

communities.

Mobile

ganisms can

escape if

or-

burial is not too severe, but storms can be lethal for many thic

a storm, can until

immobile

organisms. cover

the

bottom communi-

develop

larval settlement migration. Hinterlong

S T A G E II. S T O R M C O N D I T I O N S

barren sediment

benthic

ties again

ben-

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from

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Modified (1981).

tesy of Wayne D.

after

CourMartin.

S T A G E I. C A L M C O N D I T I O N S , P R E - S T O R M sional b a s e is often o v e r l a i n by a s h e l l - r i c h l i m e s t o n e , in w h i c h the size of shell f r a g m e n t s d e c r e a s e s u p w a r d s , w h i c h m a y i n turn b e o v e r l a i n b y l a m i n a t e d siltstone a n d b u r r o w e d m u d s t o n e . S u c h a n u p w a r d d e c r e a s e i n shell a n d s e d i m e n t g r a i n size i s c a l l e d n o r m a l g r a d i n g b y s e d i m e n t o l o g i s t s a n d reflects d e p o s i t i o n d u r i n g t h e w a n i n g p h a s e o f a s t o r m w h e n s t o r m - g e n e r ated w a v e s and c u r r e n t s w e a k e n e d a n d d e p o s i t e d the s e d i m e n t t h e y carried. L a m i n a t e d siltstone m a y d i s p l a y h o r i z o n t a l p l a n a r l a m i n a t i o n s , h u m m o c k y c r o s s - l a m i n a t i o n , o r w a v e - r i p p l e l a m i n a t i o n , all o f w h i c h c a n b e produced by strong storm-generated waves and currents.

218

A Sea without Fish

C y c l i c a l c h a n g e s in the c h a r a c t e r of storm b e d s are well d e v e l o p e d in s o m e C i n c i n n a t i a n deposits, such as the K o p e f o r m a t i o n . At a broad s c a l e , these roughly meter-thick c y c l e s consist of a m u d s t o n e - r i c h unit a n d a l i m e stone-rich unit (see F i g u r e 4.6). T h e m u d s t o n e - r i c h unit consists of 3—5 cm beds o f n o r m a l l y graded m u d s t o n e , with u n c o m m o n thin l a m i n a t e d siltstone b e d s . L i m e s t o n e - r i c h units consist of shelly l i m e s t o n e b e d s , with a lesser a m o u n t o f thin m u d s t o n e and siltstone b e d s . T h e alternation b e t w e e n these t w o units w a s originally t h o u g h t to reflect c h a n g e s in sea level, b u t r e c e n t studies suggest that these c y c l e s m a y instead reflect c h a n g e s in the a v e r a g e f r e q u e n c y and intensity of h u r r i c a n e s over tens of t h o u s a n d s of years.

C o m p a r e d to man) modern carbonate settings, O r d o v i c i a n limestone of

Oceanography

the C i n c i n n a t i area i s u n u s u a l i n several r e g a r d s . M o s t m o d e r n a n d a n cient w a r m water c a r b o n a t e d e p o s i t s c o n t a i n a w i d e v a r i e t y o f g r a i n t y p e s , i n c l u d i n g skeletal g r a i n s (the shells o f o r g a n i s m s ) , o o i d s ( s m a l l , s p h e r o i d a l , c o n c e n t r i c a l l y l a m i n a t e d grains), p e l o i d s (ovoid g r a i n s p r o d u c e d p r i m a r i l y as fecal pellets), a n d intraclasts ( p i e c e s of s e m i - c e m e n t e d c a r b o n a t e sedim e n t that h a v e b e e n e r o d e d and r e d e p o s i t e d ) . I n the t y p e - C i n c i n n a t i a n , o o i d s are a b s e n t , p e l o i d s are u n c o m m o n , a n d intraclasts o c c u r s p a r i n g l y and o n l y in p a r t i c u l a r h o r i z o n s . In c o n t r a s t , skeletal g r a i n s of b r a c h i o p o d s , b r y o z o a n s , e c h i n o d e r m s , m o l l u s c s , and trilobites d o m i n a t e m o s t l i m e s t o n e i n the C i n c i n n a t i a n (see f i g u r e 4.2). M o s t m o d e r n w a r m w a t e r c a r b o n a t e deposits c o n t a i n a b u n d a n t l i m e m u d , c a l l e d m i c r i t e , p r o d u c e d p r i m a r i l y by the p h o t o s y n t h c t i c a c t i v i t i e s of a l g a e . In c o m p a r i s o n , most l i m e s t o n e in the C i n c i n n a t i area c o n t a i n s o n l y m i n o r a m o u n t s o f m i c r i t e . S e d i m e n t s i n m o d e r n w a r m water c a r b o n a t e e n v i r o n m e n t s are p r o n e t o u n d e r g o c e m e n tation w i t h i n a few c e n t i m e t e r s below the s e d i m e n t s u r f a c e , a n d if c u r r e n t s or w a v e s strip a w a y the o v e r l y i n g u n c e m e n t e d s e d i m e n t , this e x p o s e s a hard c o n c r e t e - l i k e s u r f a c e on the sea floor, k n o w n as a h a r d g r o u n d . I lardg r o u n d s c a n b e i m p o r t a n t substrata u p o n w h i c h e n c r u s t i n g o r g a n i s m s such as bryozoans and corals may attach. A l t h o u g h hardgrounds do o c c u r i n the t y p e - C i n c i n n a t i a n , t h e y are relatively u n c o m m o n c o m p a r e d t o w a r m water settings b o t h today a n d i n t h e past. T h e f e a t u r e s that t y p i f y l i m e s t o n e o f the C i n c i n n a t i a r e a — a b u n d a n t skeletal g r a i n s , a lack o f o o i d s and p e l o i d s , m i n i m a l m i c r i t e , a n d u n c o m m o n h a r d g r o u n d s — a r e t y p i c a l of c a r b o n a t e s d e p o s i t e d t o d a y in c o o l t e m p e r a t e to p o l a r waters. The presence of cool water carbonates at tropical latitudes at first s e e m s like a p a r a d o x , but s u c h c o n d i t i o n s o c c u r today w h e r e c o a s t a l u p w e l l i n g b r i n g s c o o l water up to the s u r f a c e f r o m d e p t h s of less t h a n 200 meters. T h e s e c o o l e r waters also c o n t a i n a b u n d a n t n u t r i e n t s , w h i c h g e n e r ate p h o s p h a t e deposits. I n d e e d , the t y p e - C i n c i n n a t i a n is rich in p h o s p h a t e , p a r t i c u l a r l y in strata of M a y s v i l l i a n a g e . P h o s p h a t e is also f o u n d in a b u n d a n c e i n U p p e r O r d o v i c i a n strata n e a r N a s h v i l l e , T e n n e s s e e , s u g g e s t i n g that the entire c a r b o n a t e p l a t f o r m f r o m C i n c i n n a t i to N a s h v i l l e w a s a site of u p w e l l i n g of cool, nutrient-rich water d u r i n g m u c h of the Late O r d o v i c i a n . U p p e r O r d o v i c i a n r o c k s o f t h e C i n c i n n a t i area c o n t a i n a g r e a t e r a m o u n t o f l i m e m u d , m o r e h a r d g r o u n d s , a n d less p h o s p h a t e , w h i c h c o l -


219

l e c t i v e l y s u g g e s t a d e c r e a s e in t h e i n t e n s i t y of u p w e l l i n g in t h e latest Ordovician. A d d i t i o n a l e v i d e n c e f r o m the rich fossil f a u n a s supports the interpretation of c o o l waters, f o l l o w e d by a return to w a r m water in the latest O r d o v i c i a n . D u r i n g t h e L a t e O r d o v i c i a n , t h e western U n i t e d States and C a n a d a straddled t h e e q u a t o r . T h e i r c a r b o n a t e s e d i m e n t s are typical o f m o d e r n w a r m w a t e r settings, so their f a u n a s are interpreted to reflect w a r m water c o n d i t i o n s . T h e s e areas c o n t a i n a b u n d a n t corals a n d stromatoporoids, with a diverse array of b r a c h i o p o d s a n d trilobites. In particular, c o l o n i a l r u g o s a n and

t a b u l a t e corals (for e x a m p l e , Tetradium), solitary corals (Grewingkia,

Streptelasma), Hiscobeccus,

several

brachiopods

Lepidocyclus,

(Glyptorthis,

Holtedahlina,

Plaesiomys,

Rhynchotrema,

and Leptaena, for e x a m p l e ) , trilo-

bites (Ceraurinus), a n d diverse c e p h a l o p o d s are characteristic of this w a r m water f a u n a . T h e s e o r g a n i s m s are a b s e n t from E d e n i a n a n d M a y s v i l l i a n strata in t h e C i n c i n n a t i a r e a , b u t a p p e a r in the R i c h m o n d i a n as the l i m e stones b e g i n to reflect a return to w a r m water, low-nutrient c o n d i t i o n s . T y p e - C i n c i n n a t i a n rocks differ from typical c a r b o n a t e platform deposits in a n o t h e r s i g n i f i c a n t a s p e c t : t h e a b u n d a n c e of t e r r i g e n o u s m u d , that is, clay p r o d u c e d b y t h e w e a t h e r i n g o f silica-rich m i n e r a l s s u c h a s feldspar. T h e earliest influx o f this m u d closely c o i n c i d e s w i t h t h e b e g i n n i n g o f nutrientr i c h , c o o l water deposits a t t h e b a s e o f t h e L e x i n g t o n L i m e s t o n e , w h i c h u n d e r l i e s t y p e - C i n c i n n a t i a n strata. T h e arrival o f c o o l water, nutrients, and siliciclastic m u d a p p e a r s to h a v e b e e n triggered by the uplift of the Laconic M o u n t a i n s to t h e east. F i n e - g r a i n e d t e r r i g e n o u s clay and silt w e r e supplied b y the Q u e e n s t o n D e l t a , a s s u c h s e d i m e n t s c o u l d easily have stayed susp e n d e d in t h e water across t h e A p p a l a c h i a n Basin until d e p o s i t i o n in the C i n c i n n a t i area. T h e s e m u d s w e r e best able t o a c c u m u l a t e i n relatively c a l m e r d e e p water e n v i r o n m e n t s that w e r e less d i s t u r b e d b y storms. T h e Persian G u l f is similar in many respects to eastern L a u r e n t i a d u r i n g the O r d o v i c i a n . B o t h w e r e d e v e l o p e d as foreland basins, that is, d e e p water t r o u g h s adjacent to uplifting m o u n t a i n s . B o t h possess a c a r b o n a t e platform that dips gradually into d e e p water. T h e s e d i m e n t a r y basins are similar in size a n d c l i m a t e , and b o t h sit at subtropical latitudes p r o n e to storms. L a r g e deltas supplied b y a b u n d a n t terrigenous s e d i m e n t a d v a n c e d into both basins. T h e Persian G u l f is notably different in that it lacks u p w e l l i n g of c o o l , nutrient-rich water, w h i c h u n d e r s c o r e s that no m o d e r n setting is exactly a n a l o g o u s to C i n c i n n a t i d u r i n g the O r d o v i c i a n . S o m e have s u g g e s t e d the m o d e r n B a h a m a platform was similar to the C i n c i n n a t i area d u r i n g the O r d o v i c i a n , but the B a h a m a platform is flat-topped rather t h a n gently d i p p i n g , is not a foreland basin adjacent to uplifting m o u n t a i n s that feed a b u n d a n t terrigenous sedim e n t to a d v a n c i n g deltas, a n d lacks u p w e l l i n g of c o o l , nutrient-rich waters.

Marine

F o u r m a j o r s e d i m e n t a r y e n v i r o n m e n t s w e r e p r e s e n t d u r i n g the L a t e O r d o -

Environments of

v i c i a n o f t h e C i n c i n n a t i A r c h ( F i g u r e 15.3). T o d a y , d i s t i n c t i v e features o f

t h e Cincinnati Arch

t h e r o c k s a n d fossils c h a r a c t e r i z e t h e s e e n v i r o n m e n t s . E a c h o f t h e s e e n v i ronments is interpreted based on distinctive rock types and sedimentary s t r u c t u r e s that are f o u n d in s i m i l a r s e t t i n g s today.

220

A Sea without Fish

T i d a l flat e n v i r o n m e n t s t o d a y are flat, n e a r l y f e a t u r e l e s s a r e a s t h a t form b e t w e e n the low tide l i n e a n d the h i g h tide l i n e .

T h e s e a r e a s are

c o v e r e d daily by tides, b u t are s u b j e c t e d to e x t r e m e v a r i a t i o n s in salinity

Figure 1 5 . 3 . The four principal

sedimentary

environments

of

the

type-Cincinnatian.

and t e m p e r a t u r e on a d a i l y basis. I n U p p e r O r d o v i c i a n r o c k s o f the C i n c i n n a t i A r c h , tidal flat e n v i r o n m e n t s are p r e s e r v e d a s l a m i n a t e d t o b u r r o w e d d o l o m i t e a n d d o l o m i t i c l i m e s t o n e c o n t a i n i n g s m a l l a m o u n t s o f c l a y ( F i g u r e 15.4A). T h e p r e s e n c e

cinnatian

seas

deepened from

northward

shallow

tucky

m a g n e s i u m - r i c h brines t h r o u g h fine-grained limestone and converted it to

environments

d o l o m i t e . A l t h o u g h s u c h c o n d i t i o n s form t o d a y i n relatively arid s e t t i n g s ,

and Indiana.

the lack of o t h e r e v a p o r i t e m i n e r a l s s u c h as h a l i t e or g y p s u m in t h e s e tidal

aries

flat facies a r g u e s m o r e for a s e m i - a r i d e n v i r o n m e n t . W a v e - f o r m e d ripple-

environments

d e p o s i t e d , and d e s i c c a t i o n c r a c k s ( " m u d c r a c k s " ) i n d i c a t e the d r y i n g a n d s h r i n k i n g o f the m u d w h e n i t w a s e x p o s e d d u r i n g p r o l o n g e d low tides. S o m e o f t h e s e strata c o n t a i n n u m e r o u s c l o s e l y s p a c e d p l a n a r l a m i n a e that

water envi-

ronments in

o f d o l o m i t e s u g g e s t s s t r o n g levels o f e v a p o r a t i o n , w h i c h w o u l d h a v e d r a w n

m a r k s attest to the shallow w a t e r e n v i r o n m e n t in w h i c h t h e s e r o c k s w e r e

Cingenerally

to

central Ken-

deeper in

water Ohio

The bound-

between

these

four

correspond

to sea level,

fairweather

wave base,

and storm

wave base.

Wave base

reflects

the depth at

which

waves can move

record t h e d e p o s i t i o n o f i n d i v i d u a l layers o f c a r b o n a t e m u d d u r i n g i n c o m -

sediment on

i n g tides a n d storms o n the h i g h e s t part o f t h e tidal flat, w h i c h r e m a i n e d

and this

the sea

depth

floor

increases

a b o v e a v e r a g e h i g h tide. I n p l a c e s , t h e s e l a m i n a e are p e n e t r a t e d b y s h o r t ,

with

vertical b u r r o w s , w h i c h s u g g e s t a r e a s s o m e w h a t l o w e r o n t h e tidal flat

riod of waves,

w h e r e b u r r o w i n g o r g a n i s m s w o u l d not h a v e b e e n k i l l e d b y d r y i n g o u t a n d

which

o v e r h e a t i n g d u r i n g low tides. Elsewhere in t h e C i n c i n n a t i r e g i o n , tidal flat

storms.

The locations of

these

environments

deposits lack p l a n a r l a m i n a t i o n a n d are t h o r o u g h l y b u r r o w e d b y soft-bodied o r g a n i s m s s u c h a s p o l y c h a e t e w o r m s a n d a r t h r o p o d s . S u c h extensiveb u r r o w i n g w o u l d r e q u i r e m o r e f r e q u e n t a n d p e r s i s t e n t s u b m e r g e n c e duri n g a tidal c y c l e , as on t h e l o w e s t p o r t i o n s of t h e tidal flat. M a n y of t h e s e

the height and peincrease

changed

over

both of during

thousands

to millions of years, environments

with

shifting

northward (as shown

in

b u r r o w s are filled with the d i s t i n c t i v e g r e e n iron m i n e r a l g l a u c o n i t e . Tidal

figure) during times of

flat deposits are m o s t c o m m o n i n c e n t r a l K e n t u c k y , b u t s o m e tidal f l a t s

slowly rising sea level and

a d v a n c e d as far n o r t h w a r d as s o u t h e r n I n d i a n a , as c a n be s e e n in e x p o s u r e s

retreating

o f the S a l u d a D o l o m i t e n e a r M a d i s o n , I n d i a n a .

during

M o s t tidal flat d e p o s i t s in the C i n c i n n a t i r e g i o n are u n f o s s i l i f e r o u s , b u t l o c a l l y t h e b u r r o w e d d e p o s i t s c o n t a i n a sparse f a u n a o f b r y o z o a n s , a n d m o r e rarely o s t r a c o d s , b r a c h i o p o d s , s t r o m a t o p o r o i d s , a n d r u g o s a n a n d tabulate c o r a l s .

This restricted g r o u p o f o r g a n i s m s p r e s u m a b l y w o u l d h a v e

rising sea level. Falls in sea level resulted in

and

Paleoenvironment

the

draining of the seas from the

b e e n c a p a b l e of t o l e r a t i n g fluctuations in salinity a n d t e m p e r a t u r e . Preser-

Paleogeography

southward

times of rapidly

221

Cincinnati area.

Figure 1 5 . 4 . crop

A. Out-

photograph

laminated

of finely

dolomite

de-

posited in a tidal flat environment.

B.

photograph

of

weathering,

Outcrop rubbly

nodular

limestone

and

deposited in

mudstone

a

shallow

subtidal

environ-

ment.

C.

Outcrop pho-

tograph

of

limestone

and

interbedded mudstone

deposited in a

deep sub-

tidal environment, the

limestone

cording

re-

deposition

ing hurricanes. crop

with

beds D.

photograph

mudstone

with

of limestone stone,

durOut-

of thin

beds

and silt-

all deposited in an

offshore

environment.

v a t i o n of t h e s e fossils is t y p i c a l l y p o o r , as a result of d o l o m i t i z a t i o n , w h i c h tends to d e s t r o y fine d e t a i l s . S h a l l o w s u b t i d a l e n v i r o n m e n t s t o d a y a r e shallow

marine environ-

m e n t s below the l o w tide l i n e , b u t a b o v e fair w e a t h e r w a v e base, the d e p t h t o w h i c h w a x e s c a n stir the s e d i m e n t d u r i n g c a l m w e a t h e r . Fair w e a t h e r Behind every

the

history of

sedimentary

there lurks an tem,

rock

ecosys-

of

o c e a n i c w a v e s . I n m o d e r n c a r b o n a t e s e t t i n g s , s h a l l o w subtidal e n v i r o n m e n t s are a d j a c e n t to tidal flats a n d are c h a r a c t e r i z e d by intense b u r r o w i n g

but what one

first sees is an environment

w a v e b a s e is t y p i c a l l y o n l y a f e w m e t e r s on coasts p r o t e c t e d from large

by soft-bodied organisms such as w o r m s and arthropods. Shallow subtidal deposits are f o u n d in the

deposition.

type-Cincinnatian

l i k e w i s e c h a r a c t e r i z e d b y h i g h l y b u r r o w e d shallow

E d w a r d S. D e e v e y

a n d are

m a r i n e deposits that

g r a d e u p w a r d s into tidal flat deposits, i n d i c a t i n g that the t w o w e r e deposited

1965, 592

in laterally a d j a c e n t e n v i r o n m e n t s . In the t y p e - C i n c i n n a t i a n , shallow subtidal deposits consist of n o d u l a r to very thin w a v y - b e d d e d shelly l i m e s t o n e a n d fossiliferous m u d s t o n e ( F i g u r e 1 5 . 4 B ) . B e c a u s e o f the t h i n n e s s and w a v i ness of the l i m e s t o n e b e d s , t h e s e rocks w e a t h e r to a characteristic rubble of fist-sized l i m e s t o n e n o d u l e s .

222

A Sea without Fish

This distinctive b e d d i n g results from the per-

vasive b u r r o w i n g of the s e d i m e n t by soft-bodied o r g a n i s m s . A l t h o u g h storms c e r t a i n l y reworked the s e d i m e n t and d e p o s i t e d the c h a r a c t e r i s t i c well-sorted layers of shells overlain by layers of m u d that are preserved in s o m e p l a c e s , s u b s e q u e n t b u r r o w i n g m i x e d these l a y e r s , p r o d u c i n g p o d s o f shell-rich a n d shell-poor material. Preferential c e m e n t a t i o n o f these c h u r n e d s e d i m e n t s p r o d u c e d p o c k e t s of w e l l - c e m e n t e d shells material s u r r o u n d e d by n o n - c e m e n t e d z o n e s rich in clay. S h a l l o w subtidal l i m e s t o n e in t h e C i n c i n n a t i a r e a is l o c a l l y r i c h in p h o s p h a t e , p a r t i c u l a r l y i n t h e M a y s v i l l i a n . M u c h o f this p h o s p h a t e o c c u r s a s infillings o f b r y o z o a n z o o e c i a , the p o r o u s s k e l e t o n s o f e c h i n o d e r m s , a n d the larval shells of pelecypods, g a s t r o p o d s (such as Cyclora), a n d m o n o p l a cophorans.

The p r e s e n c e o f this p h o s p h a t e i n d i c a t e s large a m o u n t s o f d e -

c a y i n g o r g a n i c matter w i t h i n t h e s e d i m e n t . B y d i s s o l v i n g p i e c e s o f s h a l l o w subtidal l i m e s t o n e i n v i n e g a r o r d i l u t e h y d r o c h l o r i c a c i d , o n e c a n see t h e rich f a u n a p r e s e r v e d b y this p h o s p h a t i z a t i o n . S h a l l o w s u b t i d a l r o c k s are broadly d i s t r i b u t e d o v e r t h e C i n c i n n a t i A r c h a n d o c c u r f r o m t h e s o u t h e r n e d g e o f the O r d o v i c i a n o u t c r o p belt i n s o u t h e r n K e n t u c k y t o the n o r t h e r n l i m i t o f O r d o v i c i a n rocks i n c e n t r a l O h i o a n d I n d i a n a . T h e B e l l e v u e , M t . A u b u r n , O r e g o n i a , a n d W h i t e w a t e r F o r m a t i o n s all a c c u m u l a t e d within shallow subtidal e n v i r o n m e n t s . Shallow s u b t i d a l rocks a r e e x c e e d i n g l y fossiliferous i n m o s t p l a c e s , r e f l e c t i n g the a b u n d a n c e o f life i n this shallow m a r i n e habitat. M o s t c o m m o n l y , shallow s u b t i d a l r o c k s are p a c k e d with large brachiopods, s u c h as Platystrophia, Hebertella, a n d Rafinesquina. M a n y of t h e s e have t h i c k or c o a r s e l y r i b b e d s h e l l s , p r e s u m a b l y for p r o t e c t i o n a g a i n s t w a v e s a n d c u r rents. Platystrophia,

in p a r t i c u l a r , has a g r e a t l y t h i c k e n e d p e d i c l e v a l v e

n e a r the h i n g e , w h i c h w o u l d h a v e i n c r e a s e d t h e stability o f t h e shell o n t h e sea floor. D i s a r t i c u l a t i o n , b r e a k a g e , a n d a b r a s i o n o f t h e s e shells a r e w i d e spread a n d attest t o the d a m a g i n g effects o f w a v e s a n d c u r r e n t s . L a r g e b r y o z o a n s a r e often a b u n d a n t a n d i n c l u d e b r a n c h i n g , e n c r u s t i n g , sheetlike, a n d m a s s i v e f o r m s . As is t r u e for the brachiopods, t h e s e r o b u s t b r y o z o a n skeletons reflect the intensity o f w a v e s a n d c u r r e n t s i n this shallow water e n v i r o n m e n t . M o l l u s c s are p r e s e n t in shallow s u b t i d a l r o c k s , p a r t i c u larly t h e

byssally

carnivorous

attached pelecypods

cephalopod

Treptoceras,

Ambonychia

a n d Caritodens, t h e

a n d the g a s t r o p o d s Lophospira a n d

Cyclonema. Cyclonema is c o m m o n l y a s s o c i a t e d

with

c r i n o i d s , on w h i c h it

m a y have b e e n a parasite. Lophospira has b e e n i n t e r p r e t e d as a s c a v e n g e r . C r i n o i d s and trilobites o c c u r , but m o s t s p e c i m e n s a r e d i s a r t i c u l a t e d rather t h a n w h o l e , p r e s u m a b l y o w i n g not o n l y t o w a v e s a n d c u r r e n t s , b u t also burrowing organisms. Deep

s u b t i d a l e n v i r o n m e n t s t o d a y are t h o s e that lie b e l o w fair

w e a t h e r w a v e base, but a b o v e the w a v e b a s e o f all b u t t h e most p o w e r f u l storms or h u r r i c a n e s , w h i c h w o u l d have e x t e n d e d to d e p t h s of a several tens of meters. In t h e s e s e t t i n g s , t h e s e d i m e n t a r y d e p o s i t s are c h a r a c t e r i z e d b y the a l t e r n a t i o n o f s a n d y a n d shelly b e d s d e p o s i t e d d u r i n g s t o r m s and muddy b e d s that reflect quiet water d e p o s i t i o n d u r i n g w e a k s t o r m s or duri n g p e r i o d s b e t w e e n s t o r m s . D e e p s u b t i d a l e n v i r o n m e n t s are a d j a c e n t t o a n d slightly d e e p e r t h a n s h a l l o w s u b t i d a l e n v i r o n m e n t s .


223

A s o n m o d e r n s h e l v e s , storm d e p o s i t s are the m o s t c o n s p i c u o u s feature of the d e e p subtidal e n v i r o n m e n t in the t y p e - C i n c i n n a t i a n , with roughly e q u a l p r o p o r t i o n s o f t h i n t o m e d i u m - b e d d e d shelly l i m e s t o n e , l a m i n a t e d siltstones, a n d m u d s t o n e ( F i g u r e

15.4C).

B u r r o w i n g is m u c h less i n t e n s e

here than in d e e p subtidal environments, resulting in thicker and more laterally c o n t i n u o u s l i m e s t o n e b e d s . B e d s o f siltstone are c o m m o n l y rippled or display internal planar or h u m m o c k y lamination generated by s t r o n g storm c u r r e n t s a n d w a v e s . A t t i m e s , s t o r m s o c c u r r e d w i t h sufficient f r e q u e n c y that t h e y c o m m o n l y e r o d e d t h r o u g h t h e m u d s t o n e layer c a p p i n g t h e d e p o s i t f r o m t h e p r e v i o u s s t o r m , s u c h that the shelly layer f r o m o n e s t o r m w a s d e p o s i t e d d i r e c t l y o n t h e s h e l l y b e d o f t h e p r e v i o u s storm. T h i s p h e n o m e n o n , k n o w n a s a m a l g a m a t i o n , p r o d u c e s thick layers o f l i m e s t o n e w i t h s u b t l e i n t e r n a l e r o s i o n s u r f a c e s t h a t s e p a r a t e i n d i v i d u a l storm b e d s , t h e r e b y p r o d u c i n g w h a t are k n o w n a s m u l t i - e v e n t b e d s . I n s o m e c a s e s , a o n e - f o o t t h i c k b e d o f l i m e s t o n e m a y r e c o r d h a l f a d o z e n storm e v e n t s . D e e p s u b t i d a l r o c k s are a s b r o a d l y d i s t r i b u t e d o v e r t h e C i n c i n n a t i A r c h as shallow subtidal rocks.

The F a i r v i e w , C o r r y v i l l e , S u n s e t , a n d L i b -

erty F o r m a t i o n s a c c u m u l a t e d i n d e e p s u b t i d a l e n v i r o n m e n t s . D e e p subtidal rocks of the t y p e - C i n c i n n a t i a n contain an abundant and diverse fauna. Preservation is c o m m o n l y better than in shallow subtidal r o c k s , w i t h less o v e r a l l d i s a r t i c u l a t i o n , b r e a k a g e , a n d a b r a s i o n , sugg e s t i n g less e x p o s u r e t o t h e d a m a g i n g effects o f w a v e s a n d c u r r e n t s . M a n y brachiopod genera Leptaena,

m a y be p r e s e n t ,

Hiscobeccus,

Platystrophia,

i n c l u d i n g Rafinesquina, Plectorthis,

Glyptorthis,

Strophomena, and

Plaesio-

mys. A l l h a v e shells t h a t are t h i n n e r a n d finer-ribbed t h a n t h o s e in t h e s h a l l o w s u b t i d a l . B r y o z o a n s c a n b e a b u n d a n t a n d also t e n d t o b e t h i n n e r a n d less m a s s i v e t h a n i n t h e s h a l l o w s u b t i d a l . M o l l u s c s are c o m m o n , w i t h s i m i l a r f o r m s as in t h e s h a l l o w s u b t i d a l , as w e l l as t h e byssally a t t a c h e d pelecypod

Modiolopsis.

Crinoids

(Glyptocrinus,

Pycnocrinus,

and

Iocrinus)

a n d e d r i o a s t e r o i d s (Carneyella, Isorophus, a n d Streptaster) are l o c a l l y a b u n d a n t , a n d b e d s a n d p o c k e t s c o n t a i n i n g f u l l y a r t i c u l a t e d s p e c i m e n s are n o t u n u s u a l . T r i l o b i t e s (Isotelus a n d Flexicalymene) are c o m m o n b o t h as indiv i d u a l sclerites a n d a s a r t i c u l a t e d s p e c i m e n s .

The frequency of articulated

c r i n o i d s a n d trilobites s u g g e s t s early b u r i a l a n d less f r e q u e n t d i s t u r b a n c e by waves, currents, and b u r r o w i n g organisms. In the uppermost C i n c i n n a t i a n , solitary c o r a l s (Grewingkia a n d Streptelasina), a n d

the encrusting

t a b u l a t e c o r a l , Protaraea, are c o n s p i c u o u s a d d i t i o n s to t h e d e e p s u b t i d a l f a u n a . T r a c e fossils are c o m m o n Trichophycus

i n t h e siltstone b e d s . Chondrites a n d

were the burrows of deposit feeding worms or arthropods.

T h e U - s h a p e d b u r r o w s o f Diplocraterion w e r e t h e h o m e s o f a p o l y c h a e t e w o r m , b u t w h e t h e r it w a s a s u s p e n s i o n f e e d e r , a s t a t i o n a r y d e p o s i t f e e d e r , o r a n a m b u s h c a r n i v o r e i s u n c e r t a i n , a s m o d e r n e x a m p l e s o f all s u c h U t u b e b u i l d e r s are k n o w n . Paleophycus r e c o r d s t h e h o r i z o n t a l b u r r o w i n g o f another scavenging or deposit feeding w o r m . T h e t h i c k , t a b u l a r l i m e s t o n e b e d s o f t h e d e e p s u b t i d a l are well suited a s b u i l d i n g s t o n e s . M a n y old q u a r r i e s w e r e e s t a b l i s h e d i n d e e p subtidal r o c k s a n d m a n y o f t h o s e s t o n e s c a n n o w b e f o u n d i n old b u i l d i n g f o u n d a t i o n s a n d r o c k w a l l s . T w o i n t e r v a l s o f d e e p s u b t i d a l rocks f r e q u e n t e d b y

224

A Sea without Fish

q u a r r y m e n w e r e the River Q u a r r y B e d s ( n o w c a l l e d t h e Point Pleasant F o r m a t i o n ) and the Hill Q u a r r y B e d s (now c a l l e d the F a i r v i e w F o r m a t i o n ) . A l t h o u g h the River Q u a r r y B e d s n e a r C i n c i n n a t i a r e n o w largely u n d e r the O h i o River, w h o s e level w a s raised d u r i n g t h e c o n s t r u c t i o n o f d a m s , they c a n still b e s e e n n e a r Point P l e a s a n t , O h i o , a l o n g t h e crest o f the C i n c i n n a t i A r c h . M a n y o f t h e H i l l Q u a r r i e s c a n still b e s e e n i n t h e bluffs south o f the U n i v e r s i t y o f C i n c i n n a t i a n d f l a n k i n g t h e M i l l C r e e k V a l l e y . O f f s h o r e e n v i r o n m e n t s o n m o d e r n c o a s t s lie below t h e w a v e base o f m o s t s t o r m s , but a r e s o m e t i m e s a f f e c t e d b y the most severe s t o r m s a n d extend to d e p t h s of several t e n s of m e t e r s . In t h e s e m o d e r n s e t t i n g s , d e p o s i tion i s d o m i n a t e d b y m u d s , w h i c h c a n a c c u m u l a t e w h e n c u r r e n t s a n d waves are w e a k . Rare, e x c e p t i o n a l l y s t r o n g s t o r m s a r e c a p a b l e o f m o v i n g shells and s e d i m e n t s e v e n a t t h e s e d e p t h s a n d p r o d u c e t h i n storm b e d s , a l t h o u g h these m a k e u p a m i n o r i t y o f the d e p o s i t s . O f f s h o r e e n v i r o n m e n t s are adjacent t o a n d s o m e w h a t d e e p e r t h a n d e e p s u b t i d a l s e t t i n g s . In the t y p e - C i n c i n n a t i a n , o f f s h o r e r o c k s c o n t a i n a greater p r o p o r t i o n o f m u d s t o n e ( c o m m o n l y n e a r two-thirds), but i n o t h e r regards are q u i t e s i m i l a r to the deep s u b t i d a l ( F i g u r e 15.4D).

The less f r e q u e n t o c c u r r e n c e

of storm b e d s in offshore d e p o s i t s i n d i c a t e s less f r e q u e n t d i s t u r b a n c e by s t o r m - g e n e r a t e d w a v e s a n d c u r r e n t s . As a result, a m a l g a m a t i o n is m u c h less c o m m o n in t h e o f f s h o r e , and m o s t l i m e s t o n e b e d s are s i n g l e - e v e n t beds and record the passage of a single h u r r i c a n e . Many of the thick mudstone layers f o u n d in t h e offshore are also the result of storm d e p o s i t i o n , as i n d i c a t e d by the p r e s e n c e of m u l t i p l e 2-3 cm f i n i n g - u p w a r d m u d s t o n e b e d s , e a c h with a slightly silty interval at its b a s e . E a c h of t h e s e t h i n layers r e c o r d s the m i n o r d i s t u r b a n c e of the sea floor by a h u r r i c a n e , w i t h s e t t l i n g o f silt and t h e n c l a y f o l l o w i n g the s t o r m . F r e q u e n t l y , s u c h m u d layers w o u l d b l a n k e t the b o t t o m , s m o t h e r t h e f a u n a l i v i n g o n the sea floor, a n d p r e s e r v e a r t i c u l a t e d c r i n o i d s a n d trilobites. O f f s h o r e r o c k s o c c u r a s tar s o u t h a s n o r t h - c e n t r a l K e n t u c k y but e x t e n d b e y o n d the n o r t h e r n l i m i t o f O r d o v i cian exposures in central O h i o and Indiana.

The K o p e a n d W a y n e s v i l l e

F o r m a t i o n s largely reflect offshore s e t t i n g s . O f f s h o r e strata c o n t a i n a n a b u n d a n t a n d diverse f a u n a , c h a r a c t e r i z e d b y s m a l l , t h i n , a n d d e l i c a t e fossils, s u g g e s t i n g g e n e r a l l y q u i e t w a t e r c o n d i tions, e x c e p t d u r i n g rare, severe s t o r m s . C o m m o n b r a c h i o p o d s i n c l u d e t h e highly

Dalmanella a n d Sowerbyella, Pseudolingula a n d Leptobolus, w h i c h

gregarious

ticulates

and are

the

burrowing

sometimes

found

inarpre-

served inside their vertical b u r r o w s . A l t h o u g h sheet-like b r y o z o a n s d o o c c u r , t h i n b r a n c h i n g f o r m s a n d flat d i s c - s h a p e d f o r m s are m o r e c o m m o n . M o l l u s c s are d i v e r s e a n d a b u n d a n t in a few w i d e l y t r a c e a b l e h o r i z o n s , which are conspicuously poor in brachiopods and bryozoans. C o m m o n pelecypods Ambonychia Deceptrix and Rhytimya, t h e

m o l l u s c s i n c l u d e the byssally a t t a c h e d

olopsis,

the b u r r o w i n g p e l e c y p o d s

a n d Modiscavenging

Lophospira a n d Liospira, the m o n o p l a c o p h o r a n Sinuites, a n d Treptoceras a n d Cameroceras. T r i l o b i t e s are n u m e r o u s and f r e q u e n t l y fully a r t i c u l a t e d . T h e b u r r o w e r s Flexicalymene, Gravicalymene, Cryptolithus, a n d Isotelus are the m o s t c o m m o n , b u t the spiny s w i m gastropods the

cephalopods

m i n g Acidaspis c a n b e a b u n d a n t in s o m e c r i n o i d - r i c h layers. S u g g e s t i v e of


225

d e e p w a t e r s e t t i n g s is t h e p r e s e n c e of t h e blind trilobites Cryptolithus and Triarthrus in offshore strata. C r i n o i d s are also n u m e r o u s and are f r e q u e n t l y articulated.

The

most c o m m o n

genera

are

Cincinnaticrinus a n d

Fxteno-

crinus, w h o s e ossicles m a y c o m p r i s e e n t i r e b e d s o f l i m e s t o n e . G i v e n t h e t e n s o f k i l o m e t e r s o v e r w h i c h s u c h b e d s c a n b e t r a c e d , the n u m b e r o f crinoid individuals must have b e e n astronomical. As in the d e e p subtidal, t r a c e fossils are n u m e r o u s in b e d s of siltstone. Chondrites, Trichophycus a n d Paleophycus are all

Diplocraterion,

c o m m o n . T h e trilobite b u r r o w Ruso-

phycus is a l s o c o m m o n , a n d e x a m p l e s of Rusophycus m a d e by Isotelus and Cryptolithus h a v e b e e n r e p o r t e d , but o n e s p r o d u c e d b y the c a l y m e n i d s Gravicalymene

226

A Sea without Fish

a n d F l e x i c a l y m e n e are m u c h m o r e c o m m o n .

228

A Sea without Fish

16

LIFE IN THE CINCINNATIAN SEA

The Ecological Theater and the Evolutionary Play is a b o o k of f a s c i n a t i n g es-

The

says a b o u t the c o m p l e x interactions b e t w e e n the e n v i r o n m e n t and the o r g a n -

and the Evolutionary Play

isms i n h a b i t i n g it. It was written by the e c o l o g i s t G. E. H u t c h i n s o n in 1965.

G. E. H u t c h i n s o n 1965

Ecological

Theater

Hutchinson's title, an extrapolation of the S h a k e s p e a r e a n m e t a p h o r , provides a useful a n a l o g y by w h i c h to v i e w the C i n c i n n a t i a n as a Series of acts in t h e e v o l u t i o n a r y play. In c h a p t e r s 5-14 of o u r b o o k we i n t r o d u c e d t h e cast of characters, the players on the stage, of the L a t e O r d o v i c i a n sea that c o v e r e d the C i n c i n n a t i A r c h region. H a v i n g read these chapters, the reader s h o u l d be able to r e c o g n i z e the c h a r a c t e r s and know s o m e t h i n g of their r o l e s — i n particular their m o d e s of life and f e e d i n g habits. In scientific t e r m s , this is the r e a l m of a u t e c o l o g y , the r e l a t i o n s h i p of organisms of a single species with the e n v i r o n m e n t , assessing the influence o f c h e m i c a l , p h y s i c a l , a s w e l l a s b i o l o g i c a l factors. G i v e n that w e are d e a l ing w i t h o r g a n i s m s l o n g s i n c e e x t i n c t , p e r h a p s w e s h o u l d add the prefix for "ancient" and enter the a n c i e n t realm of paleoautecology. For m a r i n e o r g a n i s m s , m a j o r i n o r g a n i c factors i n c l u d e t e m p e r a t u r e ,

Figure 16.1. toceras

duseri

Whitfield), (Meek) body

Trepcrinoid

baeri

preserved

Arnold

within Richard

Davis

Waynesville

collection, Formation,

Adams Co.,

Ohio,

col-

lected by Thomas Johnson. Taeniaster

B.

m e n t c o n t e n t o f t h e water). C h a n g e s i n hydrostatic pressure a s s o c i a t e d w i t h

(Billings),

water d e p t h do not exert a m a j o r i n f l u e n c e e x c e p t in o r g a n i s m s l i k e fish

preserved

h e n c e , d e p t h itself o f t e n is c o r r e l a t e d w i t h c h a n g e s in t h e d i s t r i b u t i o n of

with

chamber.

m e n t ( b o t h c u r r e n t s and w a v e - i n d u c e d t u r b u l e n c e ) , a n d t u r b i d i t y (sedi-

o f t h e o t h e r factors listed c a n vary s i g n i f i c a n t l y w i t h w a t e r d e p t h , a n d ,

Internal

(Hall and

Xenocrinus

salinity, o x y g e n c o n t e n t o f the water, n a t u r e o f t h e sea b o t t o m , w a t e r m o v e -

with air b l a d d e r s or a i r - b r e a t h i n g , d i v i n g m a r i n e vertebrates. However, all

A.

mold of nautiloid,

mold

T.

Ophiuroid, spinosus

MUGM 28187, on

internal

of nautiloid,

Waynesville

Formation,

Butler Co.,

Ohio, scale in

mm.

C.

Trilobites, Aci-

s p e c i e s . B i o l o g i c a l factors i n c l u d e t h e m o d e o f f e e d i n g , food availability,

daspis

sp.,

preserved on

and a host of potential i n t e r a c t i o n s w i t h o r g a n i s m s of o t h e r s p e c i e s s u c h as

internal mold

predator-prey i n t e r a c t i o n s , c o m m e n s a l i s m , a n d p a r a s i t i s m .

tiloid,

In c h a p t e r 15, S t e v e n M. H o l l a n d d e s c r i b e d t h e s t a g e s e t t i n g s for t h e C i n c i n n a t i a n play, the p a l e o g e o g r a p h y a n d e n v i r o n m e n t s o f t h e L a t e O r d o v i c i a n sea in w h i c h the o r g a n i s m s lived. In order to u n d e r s t a n d t h e e n tire play, we n o w m u s t c o n s i d e r t h e ( C i n c i n n a t i a n players as an a s s e m b l e d cast o n that stage. How did the cast c h a n g e w i t h e a c h a c t , a n d how did t h e players interact with o n e a n o t h e r a s t h e plot u n f o l d e d ? R e a s s e m b l y o f the cast o f c h a r a c t e r s and the interplay b e t w e e n t h e m

CMC IP 2257, tian, bites, meeki

(Foerste),

served on

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internal mold

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ceras sp.,

OSU 50329,

Cincinnatian, Cincinnati,

their e n v i r o n m e n t , a p a l e o e c o l o g i s t m u s t first g r a p p l e w i t h a very difficult

D.

Flexicalymene

brings us to the s u b d i s c i p l i n e of s y n e c o l o g y (or, in this c a s e , p a l e o s y n e c o l -

order to d e t e r m i n e how extinct s p e c i e s w e r e i n f l u e n c e d by o t h e r s p e c i e s and

sp.,

Cincinna-

vicinity of Cincinnati,

Ohio, x 0.9.

ogy), t h e relationships o f the a n i m a l s o f the m a n y C i n c i n n a t i a n s p e c i e s that lived together w i t h their c h e m i c a l , p h y s i c a l , and b i o l o g i c a l e n v i r o n m e n t . I n

of nau-

?Treptoceras

vicinity of

Ohio,

x 2.6.

C, D from Davis et al. (2001,

figures 2, 5), and

reprinted of

question: what species a c t u a l l y lived t o g e t h e r at a g i v e n t i m e in t h e past?

229

by

Blackwell

permission Publishing.

W h a t cast w a s o n stage for a g i v e n act? A n e c o l o g i s t c a n observe a n d s a m p l e l i v i n g o r g a n i s m s i n the f i e l d , b u t t h e p a l e o e c o l o g i s t m u s t d e a l w i t h assemb l a g e s of d e a d r e m a i n s preserved in s e d i m e n t a r y rock. Factors a f f e c t i n g fossil p r e s e r v a t i o n d i s c u s s e d in c h a p t e r 1 are of t h e u t m o s t i m p o r t a n c e here. A r e t h e s e a s s e m b l a g e s representative of a c t u a l life a s s e m b l a g e s or are t h e y d e a t h a s s e m b l a g e s r e p r e s e n t i n g m i x t u r e s of o r g a n i s m s that lived at different t i m e s o r p l a c e s a n d a c c u m u l a t e d g r a d u a l l y o v e r t i m e (time-averaged assemblages) o r s u d d e n l y i n s o m e q u i c k event? H o w m u c h i n f o r m a t i o n i s m i s s i n g from the fossil record b e c a u s e of preservational bias? Fossil a s s e m b l a g e s are biased in favor of o r g a n i s m s w i t h preservable r e m a i n s w i t h hard parts like shells, skeletons, and e x o s k e l e t o n s , a n d t h e y are biased a g a i n s t o r g a n i s m s l a c k i n g h a r d parts. C r i t e r i a s u c h as t h o s e p r e s e n t e d in T a b l e 1 in chapter 1 c a n be a p p l i e d t o a n s w e r t h e s e q u e s t i o n s . T h r o u g h o u t this b o o k , e x a m p l e s o f C i n c i n n a t i a n fossils p r e s e r v e d in life position or in d i r e c t association with o r g a n isms o f o t h e r s p e c i e s p r o v i d e e v i d e n c e b y w h i c h t o d i s t i n g u i s h life assemb l a g e s f r o m d e a t h a s s e m b l a g e s . K e e p i n g t h e s e issues i n m i n d , w e c a n p r o c e e d t o e x a m i n e h o w fossil a s s e m b l a g e s vary t h r o u g h t h e C i n c i n n a t i a n a n d w h a t this reveals a b o u t C i n c i n n a t i a n p a l e o s y n e c o l o g y .

E v e r s i n c e s o m e o f t h e e a r l i e s t s t u d i e s o f C i n c i n n a t i a n fossils a n d strata, p a l e o n t o l o g i s t s h a v e r e c o g n i z e d that a s s e m b l a g e s o f o r g a n i s m s o f e x t i n c t species c h a n g e markedly through the section and show a close relationship t o t h e c h a r a c t e r o f t h e r o c k (see c h a p t e r 5). T h e q u o t a t i o n f r o m N i c k l e s (1902) in c h a p t e r 4 d e m o n s t r a t e s that he r e c o g n i z e d the p a l e o e n v i r o n m e n tal s i g n i f i c a n c e o f t h e l i t h o l o g i e s a n d their a s s o c i a t e d fossil f a u n a s . P a l e o n tologists c o m p i l e d lists o f fossils c h a r a c t e r i s t i c o f e a c h f o r m a t i o n . Fossils o f o r g a n i s m s o f s o m e s p e c i e s o c c u r i n m a n y f o r m a t i o n s and thus h a v e l o n g s t r a t i g r a p h i c r a n g e s ; fossils of o t h e r s p e c i e s are restricted to s i n g l e f o r m a t i o n s o r t h i n n e r i n t e r v a l s w i t h i n a f o r m a t i o n . E l i z a b e t h D a l v e (1948) c o m p i l e d f a u n a l lists for e a c h C i n c i n n a t i a n r o c k - u n i t b a s e d o n m a n y p r e v i o u s s t u d i e s , b u t h e r p a p e r i s n o t w i d e l y a v a i l a b l e . T h e w e l l - k n o w n biostratig r a p h i c z o n a t i o n o f t h e C i n c i n n a t i a n that i s still w i d e l y u s e d ( C a s t e r e t al. 1955; D a v i s 1985, 1992) e x p r e s s e s t h e s e f a u n a l c h a n g e s . U s i n g this k i n d o f i n f o r m a t i o n o n fossil d i s t r i b u t i o n o n e c o u l d p r e d i c t w h a t s p e c i e s m i g h t b e f o u n d in a g i v e n f o r m a t i o n , b u t t h e a s s e m b l a g e s of s p e c i e s in a f o r m a t i o n a n d their relative a b u n d a n c e w e r e less w e l l k n o w n . B e g i n n i n g i n t h e late 1960s, t h e b u r g e o n i n g s u b d i s c i p l i n e o f p a l e o e c o l o g y f o c u s e d t h e a t t e n t i o n o f p a l e o n t o l o g i s t s o n a s s e m b l a g e s o f fossils o c c u r r i n g together and their relationship to the e n c l o s i n g sedimentary m a t r i x . T o w h a t e x t e n t d i d fossil a s s e m b l a g e s r e p r e s e n t e c o l o g i c a l c o m munities c o m p a r a b l e to present-day m a r i n e b e n t h i c c o m m u n i t i e s ? M a r i n e ecologists r e c o g n i z e d c o m m u n i t i e s as recurrent assemblages of species inhabiting particular environments characterized

by particular water

d e p t h , b o t t o m t y p e , t e m p e r a t u r e , salinity, o r o t h e r c h e m i c a l o r p h y s i c a l a t t r i b u t e s . T h e y d e l i m i t e d a s s e m b l a g e s o n t h e basis o f statistical analysis o f s a m p l e s r e c o v e r e d f r o m t h e sea floor. C o m m u n i t i e s w e r e n a m e d for d o m i nant or characteristic species.

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A Sea without Fish

T h e e x i s t i n g f a u n a l lists o f C i n c i n n a t i a n fossils w e r e i n a d e q u a t e for this t y p e o f a n a l y s i s , s o p a l e o e c o l o g i s t s c o l l e c t e d n e w s a m p l e s i n w h i c h t h e a b u n d a n c e a s well a s s i m p l e o c c u r r e n c e o f fossil s p e c i e s w a s r e c o r d e d f r o m censuses of bed surfaces or bulk samples of rock. O n e of the p i o n e e r i n g s t u d i e s of this t y p e w a s that of Peter Bretsky (1970), w h o r e c o g n i z e d a series o f fossil c o m m u n i t i e s o f C i n c i n n a t i a n a g e

in

the A p p a l a c h i a n

Basin.

Bretsky's c o m m u n i t i e s w e r e c h a r a c t e r i z e d b y b r a c h i o p o d s , m o l l u s c s , a n d a n i m a l s o f o t h e r taxa a n d w e r e d i s t r i b u t e d a c c o r d i n g t o d e p t h i n p a r a l l e l b a n d s c l o s e t o t h e s h o r e l i n e o f t h e s a m e e p i c o n t i n e n t a l sea t h a t e x t e n d e d w e s t w a r d t o the C i n c i n n a t i A r c h r e g i o n . O t h e r s t u d i e s f o c u s e d o n c o m munity p a l e o e c o l o g y of the C i n c i n n a t i A r c h region, such as the work of F o x (1962, 1968), L o r e n z (1973), O l d r o y d (1978), a n d H a r r i s a n d M a r t i n (1979) (see c h a p t e r 8). S u b s e q u e n t l y , u s e o f t h e t e r m fossil c o m m u n i t y b e c a m e less f r e q u e n t , b e c a u s e i n c r e a s e d u n d e r s t a n d i n g o f t a p h o n o m i c p r o c e s s e s s h o w e d that m o s t o f t h e t i m e - a v e r a g e d a s s e m b l a g e s o f fossils are n o t directly comparable to present-day c o m m u n i t i e s . In recent q u a n t i t a t i v e studies of C i n c i n n a t i a n fossil a s s e m b l a g e s , fossil s p e c i m e n s o f i n d i v i d u a l s f r o m e x t i n c t taxa (either s p e c i e s o r g e n e r a ) are treated as v a r i a b l e s t a k e n from s a m p l e s restricted to a s i n g l e b e d s u r f a c e or d i s a g g r e g a t e d from a t h i n b e d of l i m e s t o n e or s h a l e . In e a c h s a m p l e , the a b u n d a n c e o f fossil s p e c i m e n s o f e a c h t a x o n i s c o u n t e d a n d t a b u l a t e d . In t h e study of fossil a s s e m b l a g e s in t h e C1 ( K o p e F o r m a t i o n ) d e p o s i tional s e q u e n c e , H o l l a n d , M i l l e r , M e y e r , a n d D a t t i l o (2001) c o l l e c t e d s a m ples from every fossiliferous b e d t h r o u g h a s e v e n t y m e t e r s t r a t i g r a p h i c s e c t i o n — 1 9 4 9 s a m p l e s in all. In e a c h s a m p l e , the relative a b u n d a n c e of fossils was r e c o r d e d in the field as rare (1-2 s p e c i m e n s per 1000 cm

2

of b e d d i n g

surface), c o m m o n (3-10 s p e c i m e n s p e r 1000 c m ) , or a b u n d a n t (>10 s p e c i 2

m e n s per 1000 c m ) . Fossils w e r e identified to g e n u s , a n d i n c l u d e d b r a c h i o 2

pods, c r i n o i d s , trilobites, p e l e c y p o d s , c e p h a l o p o d s , a n d g a s t r o p o d s . S o m e distinctive b r y o z o a n s w e r e identified to g e n u s , w h e r e a s others w e r e classified on the basis of c o l o n y m o r p h o l o g y as t h i n bifoliate (5 m m ) , t h i n r a m o s e or b r a n c h i n g (5 m m ) , or e n crusting. Fifty-seven taxa w e r e t a b u l a t e d f r o m t h e 1949 s a m p l e s . A f t e r rem o v a l of all taxa o c c u r r i n g in just a single s a m p l e , as well as the r e m o v a l of all s a m p l e s c o n t a i n i n g s p e c i m e n s of just a s i n g l e t a x o n , the final dataset formed a matrix of forty-six taxa or c o l o n y forms a n d 1337 s a m p l e s . Large datasets of this type c a n be a n a l y z e d u s i n g several kinds of c o m puter-driven, m u l t i v a r i a t e statistical t e c h n i q u e s . I n t h e w o r k o f H o l l a n d , Miller, M e y e r , and D a t t i l o (2001), a t e c h n i q u e c a l l e d d e t r e n d e d c o r r e s p o n d e n c e analysis ( D C A ) w a s u s e d , a l t h o u g h o t h e r t e c h n i q u e s , for e x a m p l e , cluster analysis, factor analysis, a n d p o l a r o r d i n a t i o n , p r o d u c e s i m i l a r results. D C A c a l c u l a t e s a n u m e r i c a l s c o r e for e a c h t a x o n a n d e a c h s a m p l e a n d plots t h e m a l o n g g r a p h i c a l axes that reflect similarity of taxa as g r o u p e d in s a m p l e s or similarity of s a m p l e s based on their taxa. Ecologists h a v e f o u n d that t e c h niques like D C A are very useful t o e x a m i n e h o w taxa are arrayed a l o n g these axes, w h i c h c o m m o n l y c o r r e s p o n d t o s o m e e n v i r o n m e n t a l p a r a m e t e r o r gradient. I n the analysis o f the K o p e F o r m a t i o n , n u m e r i c a l v a l u e s o f taxa a l o n g o n e DCA axis displayed a shift from l o w e r v a l u e s in the l o w e r parts of

Life in the Cincinnatian Sea

231

t h e s e c t i o n , toward h i g h e r v a l u e s m o v i n g u p - s e c t i o n . As noted in chapters 4 and 15, analyses of l i t h o l o g i c features s u c h as the shale-to-limestone ratio and b e d d i n g t h i c k n e s s d e m o n s t r a t e s that water d e p t h d e c r e a s e d from the base to t h e top o f the f o r m a t i o n .

The D C A s h o w e d that t h e c o m p o s i t i o n o f fossil

a s s e m b l a g e s also reflects this trend a n d may e v e n provide a m o r e sensitive m e a s u r e o f d e p t h c h a n g e s t h a n the c h a r a c t e r o f the rock reveals. In fossil a s s e m b l a g e s from the l o w e r K o p e ( d e e p e r water), the m o s t a b u n d a n t fossils nus,

are

the slender crinoids

the small, thin-shelled

Cryptolithus a n d

Acidaspis

larger b r a c h i o p o d

Ectenocrinus and

b r a c h i o p o d Sowerhyella, a n d

Cincinnaticri-

t h e trilobites

(see F i g u r e s 11.5,11.6). Higher in the K o p e , the

Dalmanella,

branching

bryozoans,

and

t h e trilobites

Flexicalymene a n d Isotelus b e c o m e t h e m o s t a b u n d a n t taxa. The brachiopods Zygospira a n Dalmanella a s s e m b l a g e at h i g h e r levels. At the lop of the K o p e , the larger concavo-convex abundant

brachiopods

brachiopods,

Rafinesquina a n d Strophomena are t h e m o s t

a n d t h e larger c r i n o i d Glyptocrinus r e p l a c e s t h e

s m a l l e r c r i n o i d s . I n a n earlier s t u d y o f t h e K o p e t o F a i r v i e w t o B e l l e v u e Formations,

D i e k m e y e r (1998) f o u n d s i m i l a r t r a n s i t i o n s f r o m taxa o f

s m a l l e r , m o r e d e l i c a t e a n i m a l s i n t h e K o p e t o larger, m o r e t h i c k - s h e l l e d a n d r o b u s t a n i m a l s (Platystrophia, m o r e m a s s i v e bryozoans) in the overlyi n g F a i r v i e w . S h e i n t e r p r e t e d this to be a result of a c o n t i n u a t i o n of the s h a l l o w i n g initiated d u r i n g t h e d e p o s i t i o n o f t h e K o p e s e q u e n c e .

R e c e n t research by H o l l a n d a n d P a t z k o w s k y (2007) provided similar faunal analyses for e a c h o f the C i n c i n n a t i a n d e p o s i t i o n a l s e q u e n c e s , C 1 - C 6 . I n F i g u r e 16.3 we present a t i m e e n v i r o n m e n t d i a g r a m for the entire C i n c i n n a tian based on the work by Holland and Patzkowsky. In this d i a g r a m we show the major taxa of depth-related a s s e m b l a g e s in e a c h s e q u e n c e . T h e transition from taxa of smaller, m o r e delicate a n i m a l s in d e e p e r parts of a s e q u e n c e to taxa of larger, m o r e robust o r g a n i s m s in the s h a l l o w e r parts that was found in the C1 s e q u e n c e by Holland, Miller, Meyer, and Dattilo (2001) was c o n f i r m e d a n d f o u n d to be repeated in the s u c c e e d i n g C2 and C3 s e q u e n c e s . In other w o r d s , in e a c h of these s e q u e n c e s the fossil a s s e m b l a g e s reflect a depth gradient from d e e p e r to s h a l l o w e r water.

they

also identified a s e c o n d e n v i r o n -

m e n t a l g r a d i e n t c o r r e s p o n d i n g to the n a t u r e of the substratum. A n i m a l s of taxa a l o n g o n e e n d of this g r a d i e n t c h a r a c t e r i z e soft substrata and tend to be smaller and thinner-shelled, w h e r e a s a n i m a l s of taxa arrayed toward the other e n d of the g r a d i e n t c h a r a c t e r i z e firm substrata, tend to be larger and m o r e robust, and c o m m o n l y are attached or e n c r u s t i n g in g r o w t h habit.

The R i c h m o n d i a n Invasion W i t h i n t h e u p p e r d i v i s i o n o f t h e C i n c i n n a t i a n , the R i c h m o n d i a n S t a g e , the stable p a t t e r n s of d i s t r i b u t i o n of fossil a s s e m b l a g e s f o u n d in the lower C i n c i n n a t i a n a r e d i s r u p t e d a n d r e o r g a n i z e d b y t h e influx o f o r g a n i s m s o f many new taxa, i n c l u d i n g s p e c i e s , g e n e r a , a n d classes. This influx is t e r m e d the R i c h m o n d i a n Invasion.

T h e s e i n v a d e r s did not r e p l a c e p r e - e x i s t i n g

taxa b u t instead i n c r e a s e d C i n c i n n a t i a n diversity to its h i g h e s t level. There i s a n initial p h a s e o f t h e R i c h m o n d i a n Invasion w i t h i n t h e C 4 s e q u e n c e ,

232

A Sea without Fish

hut the influx c u l m i n a t e s w i t h i n t h e C 5 s e q u e n c e w h e r e fossils o f o v e r f i f t y

The invasion was not

new g e n e r a o f c o r a l s ,

limited to particular fa-

brachiopods,

b r y o z o a n s , m o l l u s c s , trilobites, and

e c h i n o d e r m s a p p e a r ( H o l l a n d 1997; H o l l a n d a n d P a t z k o w s k y 2007; f i g u r e 16.3; see c h a p t e r s S and 9). many of the new taxa w e r e n o t p r e s e n t d u r i n g the Edenian and Maysvillian Stages of the C i n c i n n a t i a n , a l t h o u g h s o m e n e w c o m e r s represent s p e c i a t i o n w i t h i n l o n g - r a n g i n g C i n c i n n a t i a n taxa s u c h as the

brachiopods

Platystrophia a n d Strophomena

(Holland

1997).

N e w taxa a p p e a r e d i n all d e p o s i t i o n a l e n v i r o n m e n t s across the s p e c t r u m of the C i n c i n n a t i a n depth gradient, and the a n i m a l s o c c u p y the entire r a n g e o f f e e d i n g t y p e s a n d life habits ( H o l l a n d 1997). In the C4 s e q u e n c e , s o m e e l e m e n t s of the older, depth-related assemb l a g e s , s u c h as Hebertella a n d

Platystrophia,

are p r e s e n t in

cies, or

trophic groups, life-habit

rather

the

groups; Riehmondian

Invasion was a major ecological affecting the

revolution all aspects

Cincinnatian

of

seas.

Steven M. Holland 1997, 320

the shallow

subtidal z o n e , a n d Rafinesquina and Zygospira in t h e d e e p e r s u b t i d a l z o n e ( f i g u r e 16.3). In t h e C5 s e q u e n c e , a Dalmanella b r a c h i o p o d a s s e m b l a g e is a g a i n p r e s e n t in the offshore e n v i r o n m e n t s , h u t s p e c i m e n s of Zygospira also are present.

S p e c i m e n s of Rafinesquina,

b r y o z o a n s o c c u p y the d e e p e r s u b t i d a l

Platystrophia, a n d b r a n c h i n g

z o n e , b u t t h e Hebertella-Platystro-

phia a s s e m b l a g e i s g o n e f r o m t h e s h a l l o w s u b t i d a l z o n e , w h e r e a n a s s e m b l a g e of c o l o n i a l c o r a l s a p p e a r s for the first t i m e .

The d e p t h g r a d i e n t is

re-established in t h e C5 s e q u e n c e , but it is m u c h m o r e c r o w d e d w i t h taxa and has a different c h a r a c t e r t h a n in o l d e r s e q u e n c e s ( H o l l a n d a n d P a t z k o w s k y 2007). T h e C 6 s e q u e n c e i s r e p r e s e n t e d o n l y b y s h a l l o w w a t e r a s s e m b l a g e s i n c l u d i n g c o r a l s a n d robust b r a c h i o p o d s a n d b r y o z o a n s . T h e r e has b e e n considerable debate a b o u t the causes of the R i e h m o n d i a n Invasion. B e c a u s e m a i n o f the invasive taxa o c c u r i n the M i d d l e a n d U p p e r O r d o v i c i a n of the western United States a n d C a n a d a as far north as the present-day A r c t i c , it is most likely that the invasion originated from the west and northwest, tropical, w a r m water latitudes d u r i n g the L a t e O r d o v i c i a n (see chapter 15). T h e invasion was a large-scale i m m i g r a t i o n e v e n t rather t h a n an evolutionary hurst w i t h i n the C i n c i n n a t i A r c h region itself ( H o l l a n d 1997). R e t u r n i n g to the theater analogy, we find that many players (species) i n the R i e h m o n d i a n f i n a l a c t o f the C i n c i n n a t i a n a p p e a r e d i n earlier acts r e c o r d e d b y p r e - C i n c i n n a t i a n f o r m a t i o n s o f the A p p a l a c h i a n r e g i o n . T h e s e include

brachiopods

like Leptaena,

Glyptorthis, a n d

Plaesiomys ( H o l l a n d

1997), as w e l l as s t r o m a t o p o r o i d s a n d c o r a l s l i k e Tetradium. L i k e w i s e t h e s c e n e d u r i n g p r e - C i n c i n n a t i a n t i m e featured w i d e s p r e a d l i m e s t o n e d e p o s i tion in K e n t u c k y s u g g e s t i n g a w a r m e r w a t e r e n v i r o n m e n t c o n d u c i v e to carbonate deposition. A s the E d e n i a n act o f the C i n c i n n a t i a n play o p e n e d , t h e s c e n e c h a n g e d with the influx of m u d s derived from t e c t o n i c activity offstage in t h e T a c o n i c region of the A p p a l a c h i a n o r o g e n i c belt, a n d c o o l e r waters s w e p t in as c i r c u lation patterns c h a n g e d ( H o l l a n d 1997). Many players m a d e their exits, to return o n l y w h e n the s c e n e a g a i n altered i n R i e h m o n d i a n t i m e

F u r t h e r u n d e r s t a n d i n g of the

Cincinnatian

e v o l u t i o n a r y play also d e p e n d s

The Cincinnatian

o n the interplay b e t w e e n c h a r a c t e r s . H o w t h e m e m b e r s o f t h e cast inter-

Ecosystems: A Sea

acted with o n e a n o t h e r w a s o f f u n d a m e n t a l i m p o r t a n c e i n d e t e r m i n i n g t h e

w i t h o u t Fish!


233

plot a n d o u t c o m e o f t h e play. I n t e r a c t i o n s b e t w e e n o r g a n i s m s are o f m a j o r i m p o r t a n c e i n e c o l o g y a n d lead t o t h e c o n c e p t o f a n e c o s y s t e m . For a n e c o l o g i s t , a n e c o s y s t e m e n c o m p a s s e s all t h e c h e m i c a l , physical, a n d b i o l o g i c a l a s p e c t s o f t h e e n v i r o n m e n t , i n c l u d i n g the s o u r c e s o f e n e r g y a n d n u t r i e n t s e n t e r i n g t h e e n v i r o n m e n t a n d the w a y living o r g a n i s m s u s e this e n e r g y to survive a n d r e p r o d u c e . The S u n is the p r i m a r y e n e r g y s o u r c e for t h e vast majority o f e c o s y s t e m s o n E a r t h , t h e o n l y k n o w n e x c e p t i o n s b e i n g the r e c e n t l y d i s c o v e r e d d e e p sea vents, w h e r e h y d r o t h e r m a l fluids rich in n u t r i e n t s sustain m i c r o b i a l life that is, in t u r n , the basis for u n i q u e e c o systems. In shallow seas like that of the C i n c i n n a t i a n , we c a n a s s u m e that p l a n k t o n i c a s w e l l a s b e n t h i c a l g a e h a r n e s s e d solar e n e r g y a s t h e p r i m a r y p r o d u c e r s . I n d i v i d u a l s o f all o f the a n i m a l g r o u p s c o n s t i t u t e d c o n s u m e r s , f e e d i n g either directly on t h e p r i m a r y p r o d u c e r s or on other c o n s u m e r s . In order t o u n d e r s t a n d t h e n a t u r e o f C i n c i n n a t i a n e c o s y s t e m s , w e must understand how t h e c o n s u m e r s w e r e interrelated in w h a t ecologists call a f o o d c h a i n or, m o r e realistically, a f o o d w e b . H o w did O r d o v i c i a n m a r i n e ecosyst e m s c o m p a r e t o t h o s e o f t h e present-day s h a l l o w sea? D i d the n a t u r e o f the interrelationships a m o n g o r g a n i s m s a n d the form of the food w e b play a role i n d e t e r m i n i n g t h e diversity a n d a b u n d a n c e o f o r g a n i s m s i n the C i n c i n n a tian sea? In o u r a n a l o g y , did t h e interplay a m o n g c h a r a c t e r s a c t u a l l y determ i n e the cast o n stage d u r i n g a n y p a r t i c u l a r act? For a n e c o l o g i s t , i n t e r p r e t a t i o n o f a food w e b r e q u i r e s d e t a i l e d k n o w l e d g e o f t h e f e e d i n g habits a n d diets o f o r g a n i s m s o f s p e c i e s l i v i n g t o g e t h e r a t a g i v e n t i m e . A n e c o l o g i s t c a n d i r e c t l y o b s e r v e predator-prey interactions a n d c a n s a m p l e g u t c o n t e n t s o f a n i m a l s a n d their d r o p p i n g s . A n e c o l o g i s t c a n g a u g e t h e flow o f e n e r g y t h r o u g h a n e c o s y s t e m b y m e a s u r i n g t h e c a loric c o n t e n t of organisms at different levels in the food c h a i n . However, a p a l e o e c o l o g i s t w o r k i n g w i t h fossils p r e s e r v e d i n r o c k c a n n o t o b s e r v e o r s a m p l e t h e l i v i n g e c o s y s t e m d i r e c t l y a n d thus faces s o m e severe l i m i t a t i o n s in r e c o n s t r u c t i n g a " f o s s i l " e c o s y s t e m . It often is hard to d e t e r m i n e w i t h certainty w h e t h e r all fossils p r e s e r v e d in a s i n g l e b e d w e r e alive at the s a m e t i m e , b e c a u s e m a n y fossil a s s e m b l a g e s are t i m e - a v e r a g e d a m a l g a m a t i o n s of organisms of many generations. Moreover, organic remains can be m o v e d into a n a r e a o r o u t o f a n a r e a , for e x a m p l e , b y c u r r e n t s . D e s p i t e t h e s e l i m i t a t i o n s , it is rather s u r p r i s i n g to find h o w m u c h i n f o r m a t i o n the fossil r e c o r d o f t h e C i n c i n n a t i a n sea d o e s p r o v i d e , i n f o r m a t i o n that c a n b e used to answer many questions about the nature of the ecosystems. T h e m o s t d i r e c t e v i d e n c e for i n t e r a c t i o n s b e t w e e n o r g a n i s m s o f C i n cinnatian species c o m e s from a compilation of close associations a m o n g d i f f e r e n t t y p e s o f o r g a n i s m s . A s s o c i a t i o n s are essential b e c a u s e the\ c a n p r o v i d e e v i d e n c e for predator-prey r e l a t i o n s h i p s as w e l l as e v i d e n c e that t w o d i f f e r e n t s p e c i e s lived a t t h e s a m e t i m e a n d possibly a f f e c t e d o n e a n other in various ways. Besides predator-prey relationships, other c o m m o n i n t e r s p e c i f i c i n t e r a c t i o n s i n c l u d e host-parasite a s s o c i a t i o n s , c o m p e t i t i v e i n t e r a c t i o n s , m u t u a l i s m s , or c o m m e n s a l i s m s . In competitive interactions, i n d i v i d u a l s o f b o t h a s s o c i a t e d s p e c i e s are i n s o m e w a y i n h i b i t e d o r h a r m e d by t h e a s s o c i a t i o n ; in a m u t u a l i s t i c i n t e r a c t i o n , b o t h i n d i v i d u a l s derive s o m e benefit from the association; in a c o m m e n s a l i s t i c interaction, one

234

A Sea without Fish

s p e c i e s derives s o m e b e n e f i t , w h e r e a s t h e " h o s t " i s u n a f f e c t e d b y t h e prese n c e of the

symbiont.

In s o m e cases a l i v i n g a n i m a l o f o n e s p e c i e s m i g h t

b e associated w i t h n o n - l i v i n g r e m a i n s o f a n o t h e r s p e c i e s , a s i n t h e c a s e o f h e r m i t crabs o c c u p y i n g shells o f d e a d snails ( D a v i s , M a p e s , a n d K l o f a k 1999; D a v i s , F r a a y e , a n d H o l l a n d 2001). W e c o m p i l e d a v a i l a b l e i n f o r m a t i o n o n a s s o c i a t i o n s o f fossils o f C i n c i n n a t i a n s p e c i e s into t w o s u m m a r y tables. Table 2 s h o w s p o t e n t i a l predatorprey a s s o c i a t i o n s d e r i v e d from d i r e c t fossil e v i d e n c e , a n d Table 3 s h o w s all other associations reported a m o n g individuals of C i n c i n n a t i a n species or other groups.

Predator-Prey Interactions The list of potential predator-prey associations in t h e C i n c i n n a t i a n is quite short (Table 2), and the n a t u r e of the e v i d e n c e is variable.

T h r o u g h o u t the

fossil record there are rare but n o t a b l e eases of fossilized s t o m a c h c o n t e n t s that are the strongest e v i d e n c e for the diet of an e x t i n c t a n i m a l .

The only

possible instance of this in the C i n c i n n a t i a n is the o c c u r r e n c e of o s t r a c o d e s preserved w i t h i n the coralla of the r u g o s e corals asma (Elias 1984).

Grewingkia

and

Streptel-

The o s t r a c o d e s are m o s t l y articulated a n d located n e a r or

w i t h i n the alar and c a r d i n a l fossulae o f t h e coral's c a l i c e . T h e fossulae are e x p a n d e d regions b e t w e e n the septa that probably f u n c t i o n e d in water c i r c u lation w i t h i n the p o l y p a n d thus w e r e related to i n g e s t i o n of food and/or ejection of waste. A l t h o u g h it is possible that the coral ingested t h e o s t r a c o d e s as prey, Elias favored an alternative h y p o t h e s i s that the o s t r a c o d e s entered the c a l i c e w h e n the p o l y p b e c a m e d e t a c h e d from t h e side o f t h e c a l i c e and e v e n t u a l l y b e c a m e trapped b e n e a t h n e w l y secreted t a b u l a e . In this s c e n a r i o , the ostracodes m i g h t have lived s y m b i o t i c a l l y w i t h i n the coral c a l i c e . The most direct e v i d e n c e of a predator-prey relationship is the remarkable s p e c i m e n of a sea star Promopalaeaster preserved with its a r m s w r a p p e d a r o u n d a s p e c i m e n of p e l e c y p o d tentatively assigned to g e n u s Cumeamya (see F i g u r e 12.15E; Blake and C u e n s b u r g 1994). This s p e c i m e n is probably o n e of the most extraordinary fossils ever to be found in the C i n c i n n a t i a n . It provides strong e v i d e n c e that s o m e C i n c i n n a t i a n sea stars had a c q u i r e d the ability to o p e n p e l e c y p o d s seen in living asteriid sea stars, e v e n t h o u g h the present-day forms are not direct d e s c e n d a n t s of

Promopalaeaster

(Blake a n d C u e n s b u r g 1994).

T h e predatory b e h a v i o r o f s o m e i n d i v i d u a l s o f C i n c i n n a t i a n trilobite s p e c i e s was d i s c u s s e d in c h a p t e r 11.

Rusophycus

t r a c e fossils that intersect

b u r r o w s s u g g e s t that i n d i v i d u a l s o f t h e trilobite

Isotelus

preyed on some

b u r r o w i n g , p r o b a b l y s o f t - b o d i e d o r g a n i s m s . B a b c o c k (2003) i n f e r r e d that both eurypterids and

cephalopods

w e r e p o t e n t i a l p r e d a t o r s o n trilobites

d u r i n g the O r d o v i c i a n , a l t h o u g h t h e r e i s n o d i r e c t e v i d e n c e a v a i l a b l e . Specimens

of C i n c i n n a t i a n

brachiopods such

as

Rafinesquina

and

several o t h e r g e n e r a p r o v i d e e v i d e n c e for p r e d a t i o n i n t h e f o r m o f c h a r a c teristic b r e a k a g e a n d shell repair ( A l e x a n d e r 1986). A l e x a n d e r c o n s i d e r e d possible predators a m o n g sea stars, e u r y p t e r i d s , g a s t r o p o d s , a n d n a u t i l o i d c e p h a l o p o d s . H e c o n c l u d e d that t h e b e a k s o f n a u t i l o i d s w e r e m o s t likely t o h a v e inflicted the t y p e o f d a m a g e f o u n d i n t h e b r a c h i o p o d s .


235

C i n c i n n a t i a n crinoids also show e v i d e n c e o f d a m a g e and regeneration of the c a l y x , a r m s , a n d c o l u m n that is very likely the result of predation (Ausich a n d B a u m i l l e r 1993; D o n o v a n and S c h m i d t 2001; B a u m i l l e r and Gahm 2004). However there is no e v i d e n c e as to the specific predator responsible. W e s p e c u l a t e that n a u t i l o i d s m i g h t b e the m o s t likely culprits, i n v i e w o f their a b u n d a n c e a n d potential b e h a v i o r .

O t h e r Interspecific Interactions Table 3 s h o w s that v i r t u a l l y all the m a j o r i n v e r t e b r a t e g r o u p s f o u n d in the C i n c i n n a t i a n h a v e r e c o r d e d a s s o c i a t i o n s o f i n d i v i d u a l s o f taxa b e l o n g i n g t o a w i d e v a r i e t y o f g r o u p s . T h e t y p e o r n a t u r e o f the a s s o c i a t i o n s r a n g e s f r o m t h e u s e of e i t h e r a l i v i n g h o s t or d e a d r e m a i n s as a s u b s t r a t u m for e n c r u s t a t i o n , b o r i n g , o r h a b i t a t i o n ( F i g u r e 16.1), t o possible c o m m e n s a l i s m or p a r a s i t i s m . To t h e e x t e n t that a host w a s , by d e f i n i t i o n , l i v i n g at the t i m e o f t h e a s s o c i a t i o n , i t a p p e a r s that i n t e r a c t i o n s b e t w e e n i n d i v i d u a l s o f C i n cinnatian species were very c o m m o n . Detailed discussion of the nature of t h e a s s o c i a t i o n s listed c a n b e f o u n d i n t h e c h a p t e r s c o n c e r n i n g t h e t a x o n o m i c g r o u p o f e a c h host. We p r e s e n t Table 3 w i t h a s i g n i f i c a n t c a v e a t . In c a s e s in w h i c h a fossil s p e c i m e n includes an organism of o n e species attached to an individual of a n o t h e r s p e c i e s , it is n o t a l w a y s c l e a r w h e t h e r b o t h a n i m a l s w e r e alive at t h e t i m e of a t t a c h m e n t . It is p o s s i b l e that the a t t a c h e d o r g a n i s m fastened o n t o t h e o t h e r after t h e hitter's d e a t h a n d , for e x a m p l e , was u s i n g the e m p t y shell as a hard s u b s t r a t u m . An a d d e d c o m p l i c a t i o n is that v a r i o u s biologists a n d p a l e o n t o l o g i s t s h a v e n o t b e e n c o n s i s t e n t a s t o w h i c h t e r m s are u s e d for w h i c h associations.

Take t h e t e r m " e p i z o a , " for e x a m p l e . For a n association

p r o p e r l y t o b e t e r m e d " e p i z o i s m , " b o t h p a r t i e s m u s t h a v e b e e n alive a t t h e t i m e o f t h e a s s o c i a t i o n — b o t h host a n d g u e s t . H o w e v e r , the term " e p i z o a " n o t u n c o m m o n l y has b e e n u s e d i n c a s e s i n w h i c h the " h o s t " clearly was d e a d at t h e t i m e of a t t a c h m e n t a n d in c a s e s in w h i c h it is u n c l e a r w h e t h e r t h e " h o s t " w a s alive o r d e a d a t t h e t i m e o f t h e a s s o c i a t i o n . ( D a v i s , M a p e s , a n d K l o f a k 1999; D a v i s , F r a a y e , a n d H o l l a n d 2001.) M o s t of t h e c a s e s cited in Table 3 h a v e b e e n g a t h e r e d from p u b l i s h e d reports. The a u t h o r s of those reports h a v e not a l w a y s b e e n able to d e t e r m i n e or state w h e t h e r b o t h " h o s t " a n d " g u e s t " w e r e alive at the t i m e of a given association. In cases w h e r e the t y p e of association is r e c o r d e d in Table 3 as e p i z o i c , e n d o z o i c , o r o n e i n v o l v i n g b o r i n g , the putative host o r g a n i s m m a y or may n o t h a v e b e e n l i v i n g at t h e t i m e of the a s s o c i a t i o n ; the entry in the table d e p e n d s on the i n f o r m a t i o n a n d interpretations presented in the original p u b l i c a t i o n s . O n the o t h e r h a n d , i n c a s e s entered a s c o m m e n s a l o r parasitic, there is e v i d e n c e that t h e host w a s , in fact, l i v i n g at the t i m e of the ass o c i a t i o n . B i o i m m u r a t i o n is also i n d i c a t i v e of interaction b e t w e e n a living host a n d o r g a n i s m s o f a n associated s p e c i e s , b e c a u s e the associate m o d i f i e d the g r o w t h of the host in s o m e w a y as to leave e v i d e n c e that the associate was present. T h e r e are n o k n o w n d o c u m e n t e d c a s e s i n the C i n c i n n a t i a n o f either c o m p e t i t i v e or m u t u a l i s t i c interactions, L i d d e l l and Brett (19S2) reported

236

A Sea without Fish

e v i d e n c e for c o m p e t i t i o n b e t w e e n associated s p e c i e s o f e n c r u s t i n g b r y o z o ans from the M i d d l e S i l u r i a n o f I n d i a n a . C o l o n i e s o f different s p e c i e s o f b r y o z o a n s e n c r u s t i n g c r i n o i d c a l y c e s s o m e t i m e s f o r m e d raised m a r g i n s w h e r e t h e y g r e w into c o n t a c t w h e n e n crusting crinoid calyces.

The raised m a r g i n s i n d i c a t e s o m e k i n d o f "stand-

off" i n w h i c h c o l o n i e s o f e a c h s p e c i e s w e r e u n a b l e t o overgrow t h e o t h e r a n d both w e r e thus inhibited. B r y o z o a n s e n c r u s t i n g b r a c h i o p o d s i n the C i n c i n natian m i g h t also b e e x p e c t e d t o p r o v i d e this k i n d o f e v i d e n c e a l t h o u g h n o i n s t a n c e s h a v e yet b e e n reported. E v i d e n c e for m u t u a l b e n e f i t to t w o associated species is e v e n m o r e difficult to establish from fossil material.

Cincinnatian Guilds As a m e a n s of characterizing the complexity of an ecosystem, ecologists d e v e l o p e d the c o n c e p t of a g u i l d . As a p p l i e d to n a t u r a l e c o s y s t e m s , a g u i l d is d e f i n e d as "a g r o u p of s p e c i e s that exploit the s a m e class of e n v i r o n m e n t a l resources in a similar way T h i s term g r o u p s t o g e t h e r s p e c i e s , w i t h o u t regard t o t a x o n o m i c p o s i t i o n , that o v e r l a p s i g n i f i c a n t l y i n t h e i r n i c h e r e q u i r e m e n t s " ( R o o t 1967, 335). T h e p a l e o e c o l o g i s t R i c h a r d B a m b a c h a p p l i e d t h e g u i l d c o n c e p t to fossil c o m m u n i t i e s a n d e c o s y s t e m s in order to e x p l a i n h o w the e c o l o g i c a l s t r u c t u r e a n d c o m p l e x i t y o f e c o s y s t e m s has c h a n g e d o v e r e v o l u t i o n a r y t i m e ( B a m b a c h 1 9 8 3 , 1 9 9 3 ; B u s h a n d B a m b a c h 2004). B a m b a c h (19S3) first c o m p a r e d the major a d a p t i v e strategies of o r g a n isms c o m p r i s i n g the three m a r i n e " E v o l u t i o n a r y f a u n a s " : C a m b r i a n , P a l e o zoic, and M e s o z o i c - C e n o z o i c (Sepkoski 1981). B a m b a c h classified adaptive strategies a c c o r d i n g t o the m o d e o f s p a c e u t i l i z a t i o n a n d f e e d i n g habit. S u b s e q u e n t l y D r o s e r and S h e e h a n (1997) c a l l e d these broad c a t e g o r i e s " m e g a g u i l d s " and assigned b e n t h i c taxa to m e g a g u i l d s for t h e entire O r d o v i c i a n . they found that the patterns established for e p i f a u n a a n d i n f a u n a d u r i n g the O r d o v i c i a n r e m a i n e d stable for the rest o f the P a l e o z o i c Era. W e c o n s t r u c t e d m e g a g u i l d d i a g r a m s for major g r o u p s f o u n d i n the C i n c i n n a t i a n , m o d i f i e d s o m e w h a t from those o f D r o s e r a n d S h e e h a n a n d i n c l u d i n g p e l a g i c g r o u p s (Table 4a). M o s t of the g r o u p s are at t h e class level, b u t s o m e are orders. It should be r e c o g n i z e d that this c o m p i l a t i o n is c u m u l a t i v e for the entire C i n c i n n a t i a n ; thus the total n u m b e r o f g u i l d s e x c e e d s t h e total that w o u l d b e e x p e c t e d in a single c o n t e m p o r a n e o u s a s s e m b l a g e . C o m p a r i s o n o f m e g a g u i l d s t r u c t u r e o f t h e C i n c i n n a t i a n w i t h that o f t h e M e s o z o i c - C e n o z o i c reveals major contrasts ( T a b l e 4b). A m o n g the e p i f a u n a , the M e s o z o i c - C e n o z o i c i n c l u d e s m a n y s u s p e n s i o n f e e d i n g taxa a s d o e s the C i n c i n n a t i a n , but present-day g r o u p s have r e p l a c e d m a n y o f those that w e r e present d u r i n g the C i n c i n n a t i a n . P e l e c y p o d s b e c a m e d o m i n a n t , w h e r e a s brachiopods a s s u m e d a m i n o r role.

The b r y o z o a n s d o m i n a n t in the P a l e o -

zoic, the t r e p o s t o m e s , b e c a m e e x t i n c t a n d t h e c h e i l o s t o m e s b e c a m e d o m i nant. Stalked echinoderms (crinoids, blastoids, a n d cystoids) suffered major e x t i n c t i o n s at t h e e n d of the P a l e o z o i c , a n d stalked c r i n o i d s s u r v i v e d o n l y in d e e p water. The n u m b e r o f taxa o f m o b i l e e p i f a u n a l a n i m a l s , s u c h a s gastrop o d s , c r u s t a c e a n s , a n d sea u r c h i n s i n c r e a s e d m a r k e d l y . Exploitation of living space and food resources within the s e d i m e n t by


237

Figure

16.2.

Reconstruc-

tion of life on the Cincinnatian sea floor. by Anneliese Elizabeth A.

Drawing

Caster and Dalve.

From

von Engeln and Caster, Geology, 347,

1952,

of

the

by

O r d o v i c i a n g u i l d s t r u c t u r e a n d that o f the p o s t - P a l e o z o i c .

The diversifica-

tion o f b u r r o w i n g p e l e c y p o d s , g a s t r o p o d s , p o l y c h a e t e s , c r u s t a c e a n s , a n d e c h i n o i d s p o p u l a t e d b l o c k s o f t h e i n f a u n a l m e g a g u i l d s t r u c t u r e that w e r e relatively e m p t y d u r i n g t h e P a l e o z o i c ( T a b l e 4a).

figure

P e r h a p s t h e m o s t s t r i k i n g c o n t r a s t s b e t w e e n t h e O r d o v i c i a n and post-

and

P a l e o z o i c w e r e i n t h e p e l a g i c r e a l m , t h e o p e n w a t e r a b o v e t h e sea floor.

McGraw-Hill,

reprinted

i n f a u n a l o r g a n i s m s s t a n d s o u t a s o n e o f the m a j o r c o n t r a s t s b e t w e e n the

permission

McGraw-Hill

D u r i n g C i n c i n n a t i a n t i m e few g r o u p s o c c u p i e d the w a t e r c o l u m n , and a n i m a l s o f t h o s e g r o u p s differed g r e a t l v from t h o s e o f the p o s t - P a l e o z o i c

Companies.

( T a b l e 4b). It is a s t o u n d i n g to r e a l i z e that d u r i n g the C i n c i n n a t i a n there really w a s , i n t h e r e g i o n o f C i n c i n n a t i , a sea w i t h o u t f i s h , w h e r e n a u t i l o i d c e p h a l o p o d s a n d s o m e trilobites a n d e u r y p t e r i d s w e r e t h e o n l y large, actively s w i m m i n g o r g a n i s m s (Plates

13, 14;

figure

16.2).

O n l y later in t h e

P a l e o z o i c did fish b e g a n to proliferate, but m o d e r n b o n y fish did not diversify a s h e r b i v o r e s a n d c a r n i v o r e s u n t i l t h e late M e s o z o i c a n d C e n o z o i c . D u r i n g the C i n c i n n a t i a n a n d i n d e e d for m o s t o f t h e P a l e o z o i c , t h e shallow m a r i n e e c o s y s t e m was vastly different from a n y t h i n g r e s e m b l i n g a presentdav s e l l i n g . H o w c a n w e e x p l a i n t h e s e s t r i k i n g d i f f e r e n c e s ?

Was the Cincinnatian Sea a "Beggar's B a n q u e t " ? Bambach

(1993)

a r g u e d that m a j o r c h a n g e s in t h e s t r u c t u r e of m a r i n e

e c o s y s t e m s , as seen in the fossil r e c o r d , are a r e f l e c t i o n of an i n c r e a s e in 238

A Sea without Fish

T H E p r i m a r y p r o d u c t i v i t y o f the world's o c e a n s d u r i n g t h e P h a n e r o z o i c E o n . A s m e n t i o n e d earlier, w e a s s u m e that p r i m a r y p r o d u c t i o n i n t h e C i n c i n n a t i a n sea was b a s e d o n m i c r o p h y t o p l a n k t o n a s w e l l a s s o m e b e n thic m a c r o a l g a e . It is a p a r a d o x that d e s p i t e t h e h i g h a b u n d a n c e of b e n t h i c suspension feeding invertebrates in the C i n c i n n a t i a n fauna the only preserved m i c r o p h y t o p l a n k t o n i c o r g a n i s m s are t h e a c r i t a r c h s . W e r e a c r i t a r c h s t h e o n l y s u s p e n d e d food s o u r c e for a b o t t o m f a u n a d o m i n a t e d by a b u n d a n t and diverse s u s p e n s i o n feeders? W e c a n s p e c u l a t e that p e r h a p s o t h e r m i c r o p l a n k t o n i c a l g a e e x i s t e d — o n e s that l a c k e d p r e s e r v a b l e o r g a n i c c e l l w a l l s o r m i n e r a l i z e d tests. O r , p e r h a p s c l a y p a r t i c l e s s u s p e n d e d i n t h e water c o l u m n served as substrata for b a c t e r i a that f o r m e d a " m a r i n e s n o w " that n o u r i s h e d b e n t h i c s u s p e n s i o n feeders. B u t , s p e c u l a t i o n a s i d e , t h e fossil record o f m a r i n e p l a n k t o n d e f i n i t e l y i n d i c a t e s that t h e diversity o f taxa o f planktonic organisms in the C i n c i n n a t i region d u r i n g the C i n c i n n a t i a n was a b o u t fifty s p e c i e s ( C o l b a t h 1979), r e a c h e d a P a l e o z o i c m a x i m u m of t h r e e - t o four h u n d r e d s p e c i e s o f a e r i t a r c h s , t h e n suffered a d e c l i n e d u r i n g the late P a l e o z o i c a n d early M e s o z o i c . It t h e n b e g a n to i n c r e a s e d u r i n g t h e Jurassic a n d C r e t a c e o u s , w i t h t h e a p p e a r a n c e o f p r e s e n t - d a y g r o u p s s u c h as dinoflagellates, calcareous n a n n o p l a n k t o n , and diatoms (Tappan and L o e b l i c h 1973). If t h e diversity of p l a n k t o n i c o r g a n i s m s is c o r r e l a t e d in s o m e w a y w i t h a b u n d a n c e a n d p r o d u c t i v i t y , t h e n t h e fossil r e c o r d o f m a rine p l a n k t o n

indicates a m a r k e d increase in productivity d u r i n g the

P h a n e r o z o i c ( B a m h a e h 1993).

The C i n c i n n a t i a n s e a , d e s p i t e its s e e m i n g

organic a b u n d a n c e , may, in fact, have b e e n poor in food resources c o m pared to present-day s e t t i n g s . A l t h o u g h the earliest spores of land plants date from the O r d o v i c i a n , terrestrial regions of the Earth r e m a i n e d essentially d e v o i d of w i d e s p r e a d plant cover until the late D e v o n i a n ( B a m h a e h 1993). B a m h a e h s u g g e s t e d that the rise of land plants had a p r o f o u n d effect on m a r i n e e c o s y s t e m s , b e c a u s e rivers b e g a n to carry vast a m o u n t s of o r g a n i c matter a n d nutrients into the sea. T h i s o r g a n i c matter provided a major new food r e s o u r c e for b e n t h i c m a r i n e o r g a n i s m s and c o n t r i b u t e d to the great diversification of i n f a u n a l guilds in the post-Paleozoic. ( T h e s e had b e e n poorly d e v e l o p e d in the C i n cinnatian.) Increased o r g a n i c input from the land also increased the supply of nutrients to coastal m a r i n e e n v i r o n m e n t s , in turn e n h a n c i n g overall m a rine productivity. B a m h a e h a r g u e d that i n c r e a s i n g levels of m a r i n e productivity enabled an increase in m a r i n e biomass, diversity, and f u n c t i o n a l versatility that is reflected in the fossil record of p o s t - P a l e o z o i c m a r i n e e c o s y s t e m s . The vastly different, s e e m i n g l y a l i e n w o r l d o f t h e C i n c i n n a t i a n sea c a n thus h e u n d e r s t o o d a s t h e p r o d u c t o f a p e r i o d i n E a r t h history w h e n the c a p a c i t y of t h e sea to s u p p o r t lite was a m e r e f r a c t i o n of w h a t it b e c a m e through subsequent Phanerozoic time.

The m o d e s o f life, b o d y s i z e , a n d

overall a b u n d a n c e o f m a r i n e life i n t h e C i n c i n n a t i a n o f t h e C i n c i n n a t i r e g i o n w e r e all l i m i t e d b y t h e a m o u n t a n d q u a l i t y o f food r e s o u r c e s available.

The " b e g g a r ' s b a n q u e t " m a y h a v e d e f i n e d t h e r u n n i n g plot o f t h e

C i n c i n n a t i a n play. T h e u l t i m a t e o u t c o m e o f this plot i s h i d d e n f r o m v i e w i n t h e C i n c i n nati region b e c a u s e the e v i d e n c e o f t h e c l o s i n g a c t s o f t h e O r d o v i c i a n r e -


239

Figure 1 6 . 3 . Time-environment diagram

for the

Cincinnatian Series.

The

vertical axis shows

the

timescale and six major shallowing-upward quences

of the

seCincinna-

tian (see chapters 4 and 15).

G = Gamachian Stage

(not preserved in nati region).

Cincin-

The horizon-

tal axis shows the major environments

of the

Cin-

cinnatian (see chapter Offshore

15).

environments

are located

towards

the

present north in Ohio and westward in Indiana, shoal and lagoon ments are

and

environ-

located

toward

the present south in

Ken-

tucky (see Plate 12). FWB =

fairweather wave base,

SWB = storm wave base. Letter-codes

indicate

ma-

jor fossils characteristic of assemblages each

found

sequence

ronment,

in

and

envi-

defined as

fos-

sils occurring in >20% of samples ting.

from each set-

Letter-codes as fol-

lows: corals: Gr = Gewingkia,

Sp =

Streptelasma, radium,

Te =

Pr -

Tet-

Protaraea;

bryozoans: bf = bifoliate forms,

en = encrusting

forms, nr = thin ramose forms, ra = ramose forms; brachiopods: Da = Dalmanella, tella.

He

Hi =

=

Heber-

Hiscobeccus,

Ht = Holtedahlina,

Lp =

c o r d w a s o b l i t e r a t e d b y s u b s e q u e n t e r o s i o n . T h e m i s s i n g script, a s read e l s e w h e r e , tells u s that s w e e p i n g e n v i r o n m e n t a l c h a n g e s b r o u g h t a b o u t

Leptaena,

PI = Plat-

m a s s e x t i n c t i o n s o f m a n y O r d o v i c i a n players w o r l d w i d e .

ystrophia,

Pp = Plat-

these extinctions are debated. T h e y apparently were c o m p l e x and seem to

ystrophia

ponderosa,

= Plectorthis,

Ra

=

Rafinesquina,

Re

=

rorsirostra, chotrema, byella,

Pt Ret-

Rn = RhynSo

=

Sower-

St =

The causes of

h a v e i n v o l v e d a g l o b a l ice a g e , a l o n g w i t h c h a n g e s i n sea level a n d o c e a n c h e m i s t r y ( H a l l a m a n d W i g n a l l 1997). T h e shallow seas that a g a i n c o v e r e d t h e r e g i o n o f t h e C i n c i n n a t i A r c h d u r i n g t h e e n s u i n g S i l u r i a n act w e r e p o p u l a t e d w i t h m a n y f a m i l i a r players a n d roles, yet t h e cast o f c h a r a c t e r s r e p r e s e n t s a c l e a r l y d i f f e r e n t t r o o p of players on a new stage setting. W h e n w e s e a r c h t h e seas o f t h e p r e s e n t day for a n y t h i n g r e s e m b l i n g

Strophomena,

Zy

=

Zy-

240

the C i n c i n n a t i a n e c o s y s t e m s , a revival o f t h e C i n c i n n a t i a n play, w e are

A Sea without Fish

hard pressed t o f i n d m a i n g o o d a n a l o g u e s . O f c o u r s e , e x t i n c t i o n has s w e p t

gospira; trilobites; ca =

a w a y v i r t u a l l y all t h e taxa o f t h e o r g a n i s m s that i n h a b i t e d t h e C i n c i n n a t i a n

calymenid,

sea, i n c l u d i n g e n t i r e m a j o r g r o u p s s u c h a s g r a p t o l i t e s , c o n u l a r i i d s , trilo-

thus, Is = Isotelus; ostra-

bites, e u r y p t e r i d s , a n d e d r i o a s t e r o i d s . H o w e v e r , t o d a y w e c a n f i n d rather restricted r e g i o n s w h e r e t h e sea f l o o r i s c o v e r e d w i t h b r y o z o a n s , s u c h a s t h e s h e l f off S o u t h A u s t r a l i a ( B r a d s t o c k a n d C o r d o n 1983; H a g e m a n e t al.

Ct =

Cryptoli-

c o d e s = os; g a s t r o p o d s = ga; p e l e c y p o d s ; Am = Ambonychia,

by

= inde-

terminate pelecypod,

2000). N e w Z e a l a n d , isolated i n t h e s o u t h w e s t e r n P a c i f i c , h a r b o r s t h e

= Carotidens,

greatest diversity o f l i v i n g b r a c h i o p o d s ; e l s e w h e r e t h e s e a n i m a l s are b u t

omorphid pelecypod;

m i n o r c o m p o n e n t s of shallow water c o m m u n i t i e s . C l o s e r to the area of the

noids.

C i n c i n n a t i a n , t h e S a n Juan Islands in t h e P a c i f i c N o r t h w e s t s u p p o r t a di-

nus,

verse a n d a b u n d a n t fauna that i n c l u d e s m a n y P a l e o z o i c e l e m e n t s s u c h a s

Gl = Glyptocrinus,

e c h i n o d e r m s , b r y o z o a n s , b r a c h i o p o d s , solitary c o r a l s , a n d s p o n g e s . H o w ever, t h e s e relicts are a m e r e f r a c t i o n of a m o r e d i v e r s e f a u n a rich in m o l l u s c s , c r u s t a c e a n s , a n d f i s h — a l l g r o u p s that proliferated i n t h e p o s t - P a l e o -

cri-

Ci = CincinnaticriEc

=

Xenocrinus; gra.

Ca

mo = modi-

Ectenocrinus, Xe =

graptolites

those

invading

during

the

region

Richmondian

z o i c . P r e s e n t - d a y t r o p i c a l reefs far s u r p a s s t h o s e o f t h e O r d o v i c i a n i n

invasion.

diversity a n d a b u n d a n c e , a n d yet t h e r e are c e r t a i n reef-related habitats t h a t

rived from

Holland and

mirror, t o s o m e e x t e n t , t h e P a l e o z o i c . I n A u s t r a l i a ' s G r e a t B a r r i e r Reef,

Patzkowsky

(2007);

d e e p e r , soft s e d i m e n t b o t t o m s l o c a t e d b e l o w t h e c o r a l - d o m i n a t e d shallow

this publication

reefs h a v e a P a l e o z o i c a s p e c t , rich in a l g a e , s p o n g e s , solitary c o r a l s , b r y o z o a n s , a n d c r i n o i d s ( M e s s i n g e t al. 2006). I n d i v i d u a l s o f t h e c h a m b e r e d

=

Italicized fossils are

bution

Information

desee

for distri-

of additional

fossils.

Nautilus, the o n l y l i v i n g d e s c e n d a n t s o f the n a u t i l o i d c e p h a l o p o d s o f t h e P a l e o z o i c , also s u r v i v e at d e p t h s of 100 m b e l o w t h e tops of t h e reefs of t h e Pacific. L i k e w i s e , the o n l y l i v i n g s t a l k e d c r i n o i d s are restricted t o d e p t h s greater t h a n 100 i n ( M e y e r 1997). C o l l e c t i v e l y , t h e s e e x a m p l e s o f p r e s e n t day survivors f r o m t h e past a n d P a l e o z o i c - l i k e c o m m u n i t i e s s h a r e t h e c h a r acteristics o f e x i s t e n c e i n s o m e isolated o r restricted s e t t i n g s w h e r e d o m i n a n c e b y the m o r e typical shallow m a r i n e f a u n a is, t o s o m e d e g r e e , r e l a x e d . I t i s o n l y u n d e r s u c h a n o m a l o u s c o n d i t i o n s that o r g a n i s m s o f m a n y a n c i e n t g r o u p s c a n f l o u r i s h a n d p r o v i d e u s w i t h a f l e e t i n g g l i m p s e o f the a n c i e n t O r d o v i c i a n sea that o n c e c o v e r e d t h e C i n c i n n a t i r e g i o n . Predator

Prey

References

ostracodes?

Elias 1 9 8 4

Nautiloids

brachiopods

Alexander 1 9 8 6

trilobites

Babcock 2003

crinoids

Prey among Taxa

Rugose corals

Unspecified

Table 2. Predators and

Ausich and Baumiller 1993; D o n o van and Schmidt 2001; Baumiller and Gahn 2004

Trilobites

worms

Babcock 2003; Brandt et al. 1995

Eurypterids

trilobites

Babcock 2003

Asteroids

pelecypods

Blake and Guensburg 1 9 9 4


241

Cincinnatian

Table among

3.

Associations

Individuals

cinnatian

ARRANGED BY "HOST"

of Cin-

Taxa

Host

Associate

Type of Association

References /

bioimmuration; epizoism

Wilson, Palmer,

pelecypods

boring

Pojeta and Palmer (1976); Wilson and Palmer (1988)

bryozoan

encrustation (post-

Wilson, Palmer,

mortem);

and Taylor (1994)

[Annotations]

PROTISTA foraminifers

bryozoan

and Taylor (1994)

PORIFERA stromatoporoids

CNIDARIA hydrozoan

dwelling inside empty shell corals

algae, fungi

boring

Elias and Lee (1993)

corals

epizoism

Elias (1983)

bryozoans

encrustation:

Bassler(1953)

epizoism bryozoans

encrustation:

Elias (1983)

epizoism worms

boring

Elias (1983)

(at least s o m e

[Trypanites in

during life of host)

Grewingkia]

worms

boring

Elias (1986)

algae

boring

Kobluk and Risk (1977)

corals

epizoism

Elias (1983)

post-mortem

Shrake(1989)

BRACHIOPODA brachiopods

brachiopods

attachment

bryozoans

encrustation; epizoism

Nicholson (1875)

bryozoans


Wilson, Palmer, and Taylor (1994)

"boring";

Anstey and Wil-

presumably post-

son (1996)

bryozoans

mortem bryozoans

"boring"

Pohowsky (1974, 1978)

bryozoans

post-mortem attachment

242

A Sea without Fish

Shrake(1989)

ARRANGED BY "HOST" Host

Associate

Type of Association

References /

bryozoans

encrustation; ? epizoism

Anstey and Wilson (1996) [Corynotrypa on interior of brachiopod shell]

bryozoans

encrustation; ?

Anstey and Wilson (1996) [Cuffeyella on interior of brachiopod shell]

[Annotations]

post-mortem

bryozoans

encrustation

Ulrich (1879)

bryozoans

encrustation

Ulrich (1883)

brachiopods

epizoism

Alexander and

Cornulites

? commensalism

Morris and Rollins (1971)

post-mortem

Shrake (1989)

Scharpf (1990)

crinoids

attachment edrioasteroids

epizoism

Richards (1972)

epizoism or

Meyer (1990)

commensalism gastropods

Sphenothallus

borings

Fenton and Fenton (1931)

borings

Bucher (1938)

epizoism

Neal and Hannibal (2000)

stromatopor-

epizoism

Richards (1972);

oids

Alexander and Scharpf (1990)

ECTOPROCTA bryozoans

corals

epizoism

Elias (1983)

brachiopods

epizoism

Richards (1972)

brachiopods

aegism; epizoism

Shrake (1989)

bryozoans

encrustation; epizoism

Nicholson (1875)

bryozoans

encrustation

Ulrich (1879a)

bryozoans

encrustation

Ulrich (1883)

bryozoans

aegism; epizoism

Shrake (1989)

bryozoans

bioimmuration;

Wilson, Palmer,

epizoism

and Taylor (1994)

bioclaustration; parasitism;

son (1988)

Catellocaula

Palmer and Wil-

epizoism


243

A R R A N G E D BY "HOST Host

Associate

Type of Association

Cornulites

References / [Annotations]

epizoism; ?

Morris and Rollins

commensalism

(1971)

encrustation and

Baird, Brett, and

intergrowth

Frey(1989)

pelecypods

boring

Wilson and

Sanctum

boring

Erickson and

Sphenothallus

epizoism

cornulitids

Palmer (1988) Bouchard (2003) Bodenbender et al. (1989) trilobites "worms"

aegism —

borings

Trypanites

Shrake(1989) Palmer and Wilson (1988)

CORNUUTIDS cornulitids

bryozoans

encrustation and intergrowth

cornulitids

bryozoans


Baird, Brett, and Frey (1989) Wilson, Palmer, and Taylor (1994)

MOLLUSCA Mollusca —

brachiopods

epizoism

gastropods Mollusca —

Cornulites


Morris and Felton (1993)

Cornulites

encrustation;

S. A. Miller

? commensalism

(1874c)

commensalism

Morris and Rollins (1971);

gastropods

Morris and Felton (1993) Mollusca —

Cornulites


? epizoism: ?

Richards (1974)

commensalism trilobites

? endozoism ?

Brandt (1993)

bryozoans

encrustation

Ulrich (1883)

Cornulites

epizoism or

Morris and Rollins (1971)

gastropods Mollusca — monoplacophorans Mollusca — nautiloids

brachiopods — (inartic.)

encrustation

Mollusca —

bryozoans

encrustation;

nautiloids

244

commensalism

A Sea without Fish

Davis and M a p e s (1996)

epizoism

Nicholson (1875)


Mollusca

Associate

bryozoans

"nautiloids" — actinoceroids endoceroids

bryozoans

Type of Association

References/ [Annotations]

epizoism; ?

Frey (1988, 1989);

commensalism

Baird et al. (1989)

encrustation

Davis and M a p e s (1996)

presumably epizoism;

nautiloids

? commensalism bryozoans

encrustation

bryozoans

encrustation

Ulrich (1879a) U. P. James (1884b)

bryozoans

encrustation

Ulrich (1883); Bassler (1953)

bryozoans

encrustation (post-


mortem); dwelling inside empty shell Cornulites

? epizoism ? commensalism

Richards (1974)

hydrozoan

encrustation (postmortem); dwelling inside empty shell


stromatoporoid

encrustation

J. F. James (1886)

stromatoporoid

encrustation

Baird, Brett, and

trilobites

? incolenism

Davis et al. (2001)

epizoism or

Morris and Rollins (1971);

Frey (1989)

Mollusca —

Cornulites

pelecypods

commensalism

Morris and Felton (2003) ARTHROPODA trilobites

bryozoans

epizoism

Brandt (1996)

trilobites

Cornulites

epizoism

Morris and Rollins (1971); Brandt (1996)

Echinodermata — crinoids

brachiopods

aegism; epizoism

Shrake (1989)

Echinodermata —

brachiopods —

commensal

Sandy (1996)

bryozoans

encrustation

Ulrich (1883)

bryozoans

encrustation: epizoism

Bassler (1953)

ECHINODERMATA

crinoids Echinodermata —

Zygospira

crinoids Echinodermata — crinoids


245


Echinodermata

—

Associate

Type of Association

References/ [Annotations]

byroniids

parasitism

Warn (1974); Welch (1976);

crinoids

Malinky et al. (2004) Echinodermata

—

Cornulites

commensalism

crinoids

Morris and Rollins (1971); Morris and Felton (1993, 2003); Richards (1974)

Echinodermata —

gastropods

commensalism

gastropods

? parasitism ?

crinoids Echinodermata crinoids "WORMS" (see also: cornulitids)

246

A Sea without Fish

—

Bowsher (1955); Morris and Felton (1993) Baumiller and Gahn (2002)

SUSPENSION

HERBIVORE

chitinozoans (?) conodonts graptolites trilobites (pt)

SUSPENSION trilobites (pt)

EPIFAUNA

MOBILE

ATTACHED LOW

ATTACHED ERECT

RECLINING

stromatoporoids (pt) tab., rugose corals (pt) bryozoans craniate brachs rhynch. brachs bivalves cornulitids edrioasteroids cyclocystoids sponges conulariids stromatoporoids (pt) tabulate corals (pt) bryozoans rhombiferans crinoids

rugose corals (pt) strophomenate brachs tentaculitids hyolithids stylophorans

DEPOSIT

PRIMARY PRODUCERS

CARNIVORE cephalopods eurypterids

acritarchs

HERBIVORE

monoplacophorans monoplacophorans gastropods gastropods ostracods trilobites ostracods ophiuroids, asteroids (pt)

CARNIVORE trilobites (pt) asteroids

SUSPENSION

DEPOSIT

CARNIVORE

rostroconchs SHALLOW PASSIVE

SHALLOW ACTIVE

Ungulate brachs bivalves Diplocraterion

bivalves polychaetes

polychaetes

DEEP PASSIVE

DEEP ACTIVE

Table 4 A . tian

Marine

Modified and


247

Type-CincinnaGuilds

after

Sheehan

Droser (1997).

PELAGIC

SUSPENSION gastropods malacostracans mammals

SUSPENSION

ATTACHED LOW

ATTACHED ERECT

RECLINING

bony fish mammals

DEPOSIT

cephalopods dinoflagellates chondrichthyans coccolithophores bony fish diatoms reptiles mammals

chitons gastropods ostracods malacostracans echinoids

sponges corals bryozoans brachiopods polychaetes bivalves barnacles sponges corals bryozoans crinoids corals (pt) bivalves

SHALLOW PASSIVE

A Sea Without Fish-- Life in the Ordovician Sea of the Cincinnai Region

A Sea without Fish: Life in the Ordovician Sea of the Cincinnati Region (Life of the Past)

Ancient Fishing and Fish Processing in the Black Sea Region (Black Sea Studies)

Fish Invasions of the Mediterranean Sea

People And The Sea (Life in the Sea)

The Security of the Caspian Sea Region (A Sipri Publication)

Sea without Shore

The Saltwater Wetland (Life in the Sea)

The Continental Shelf (Life in the Sea)

The Open Ocean (Life in the Sea)

The Coral Reef (Life in the Sea)

Governing a Common Sea: Environmental Policies in the Baltic Sea Region

Home a the Sea

Scorpion in the Sea

The Sea

The Sea

The Sea

River in the Sea

Dragon in the Sea

The Sea

The Sea

The Sea

The Sea

Heart of the Sea

The Sea of Trolls

Scend of the Sea

Heart of the Sea

The Sea Of Death

The Sea of Trolls

Cathedral of the Sea

The Sea of Monsters

A Sea Without Fish-- Life in the Ordovician Sea of the Cincinnai Region

A Sea without Fish: Life in the Ordovician Sea of the Cincinnati Region (Life of the Past)

Ancient Fishing and Fish Processing in the Black Sea Region (Black Sea Studies)

Fish Invasions of the Mediterranean Sea

People And The Sea (Life in the Sea)

The Security of the Caspian Sea Region (A Sipri Publication)

Sea without Shore

The Saltwater Wetland (Life in the Sea)

The Continental Shelf (Life in the Sea)

The Open Ocean (Life in the Sea)

The Coral Reef (Life in the Sea)

Governing a Common Sea: Environmental Policies in the Baltic Sea Region

Home a the Sea

Scorpion in the Sea

The Sea

The Sea

The Sea

River in the Sea

Dragon in the Sea

The Sea

The Sea

The Sea

The Sea

Heart of the Sea

The Sea of Trolls

Scend of the Sea

Heart of the Sea

The Sea Of Death

The Sea of Trolls

Cathedral of the Sea

The Sea of Monsters

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