Zonation and correlation of Middle Boreal Bathonian to Lower Callovian (Jurassic) ammonites, Salmon Cache Canyon, Porcupine river, Northern Yukon

GEOLOGICAL SURVEY OF CANADA BULLETIN 358

ZONATION AND CORRELATION OF MIDDLE BOREAL BATHONIAN TO LOWER CALLOVIAN (JURASSIC) AMMONITES, SALMON CACHE CANYON, PORCUPINE RIVER, NORTHERN YUKON

T.P. Poulton

1987

©

Minister of Supply and Services Canada 1987

Available in Canada through authorized bookstore agents and other bookstores or by mail from Canadian Government Publishing Centre Supply and Services Canada Ottawa, Canada KIA OS9 and from Geological Survey of Canada offices: 601 Booth Street Ottawa, Canada K lA OE8

3303-33rd Street N.W., Calgary, Alberta T2L 2A7 A deposit copy of this publication is also available for reference in public libraries across Canada Cat. No. M42-358E Canada: $13.00 ISBN 0-660-12512-9 Other countries: $15.60 Price subject to change without notice

Critical readers T. Birkelund J.H. Callomon E.T. Tozer

Scientific editor N.C. Ollerenshaw

Editor J.M. MacGillivray

Technical editor and layout L. Machan-Gorham E.G. Snow

Word processing and production P. Greener M. Varalta

A. Seif H. King

Author's address Institute of Sedimentary and Petroleum Geology 3303 - 33rd Street N. W. Calgary, Alberta T2L 2A7

Artwork by CARTOGRAPHY UNIT Institute of Sedimentary and Petroleum Geology Original manuscript submitted: 1982-09-07

Approved for publication: 1985-12-02

Cover O;rycerites birkelundi from GSC locality 93570, see Plate 35.

PREFACE Ammonites have long been recognized to be among the finest tools for correlation of Mesozoic rocks and have served as the inspiration for many current Ideas on fossil species concepts, on the style and rate of evolution, and on paleobiogeographic provincialism. This study describes the ammonites from a single, richly fossiliferous, and well exposed locality in northern Yukon where a succession of seven faunas is present. A new zonation for northwestern Canada is proposed based on this succession. The ammonites are mainly Boreal, and correlations of each zone with the published successions across the Arctic are discussed. The presence of some fossils with Pacific affinities contributes to resolution of the long-standing problems of correlation of Bathonian zones intercontinentally, via northern Yukon and Western Canada. Eight new species and one new genus are described. Stratigraphic paleontological studies such as this lead to the development of widely accepted standards of correlation, essential tools in reconstructing the geological framework of Canadian sedimentary basins and evaluating their mineral and hydrocarbon resources.

OTTAWA,1986

ReA. Price Director General Geological Survey of Canada

PRB:ACE On reconnalt depuis longtemps l'utilite des ammonites dans la correlation des roches mesozolques; elles ont servi egalement de guide dans l'evolution de concepts traitant des especes fossiles, par leur style et leur avancement evolutlt, et ainsi que leur provincialisme palebiogeographique, Cette etude decrit des ammonites provenant d'une localite unique, tres fossififere du Yukon septentrional ou se situe une succession comprenant sept faunes. Cette succession a fourni la base de donnees qui nous permet de proposer une nouvelle zonation pour le Canada du nord-ouest. Les ammonites sont, pour la plupart, boreales, et des correlations de chaque zone avec des successions de l'Arctique deja rapportees y sont dlscutees. La presence de quelques fossiles ayant des affinites avec ceux du Pacifique contribue a la resolution de problernes de longue duree portant sur la correlation intercontinentale des zones bathoniennes, via le Yukon septentrional et le Canada occidental. On ydecrlt huit nouvelles especes et un nouveau genre.

a

Des etudes stratigraphiques et paleontologiques telles que celle-ci nous rnene I'elaboration des standards de correlation reconnus &lobalement. De tels standards sont essentiels a la comprehension de la structure geologique des bassins sedimentaires due Canada et a l'evaluation de leur potentiel econornlque en ressources minerales et en hydrocarbures.

OTTAWA,1986

R.A. Price Le directeur general de la Commission geologlque du Canada

CONTENTS 1 2 2 3 3 3 3 7 7 9

l2 l2 l2 l2 L2 L2

13 13 13 14 26 27 28 28 28

28 29

30 30 30

31 32 32

32 32 33 33 33 33 33 34 34 35

36 36 37 37 38 39 -.0 -.0 "'1 "'2 '2 '3 '"' '5 "'6 46 "'6 "'6

.7

.7 U

.9 49 )0

'2

'3 '3 D '3

Abstract/Resume Introduction Faunal provincialism Previous work Present study and acknowledgments Geological setting Regional stratigraphic relationships Local stratigraphic relationships Biostratigraphic subdivisions Spathi Zone (Beds 2-14) Porcupinensis Zone (Beds 15-25) Amundseni Zone (Beds 26-45) Frami Zone (Beds 46-47} Unnamed Zone (Bed 48) Harlandi Zone (Bed 53) Ishmae Zone (Beds 55-60) Bamstoni Zone (Bed 62) Unnamed Zone (Bed 66) Bodylevslcyi Zone (Bed 68) Description of the section Fossil localities Correlation Lower Boreal Bathonian Middle Boreal Bathonian Spathi Zone Porcupinensis Zone Amundseni and Frami Zones Upper Boreal Bathonian Harlandi Zone Ishmae Zone Barnstoni Zone Lower Callovian Bodylevslcyi Zone Younger zones Taxonomic paleontology Species concept Dimorphism Suborder Ammonitina Superfamily Stephanocerataceae Family Cardioceratidae Subfamily Arctocephalitinae Genus Arctocephalites Arctocephalites spathi n, sp, Arctocephalites ellipticus(?) Arctocephalites sp. A aff. A. sphaericus Arctocephalites sp, B aff. A. sphaericus Arctocephalites porcupinensis n, sp, Arctocephalites callomoni Arctocephalites sp, A aff. A. nudus Arctocephalites sp, B aff. A. nudus Arctocephalites arcticus Arctocephalites praeishmae n, sp, Arctocephalites amundseni n, sp, Arctocephalites kigilakhensis Arctocephalites frami n, sp, Arctocephalites sp, A Arctocephalites sp, B Arctocephalites sp, C Arctocephalites sp, D Arctocephalites(?) sp, E Arctocephalites(?) freboldi Arctocephalites(?) sp, aff. A.(?) freboldi Arctocephalites(?) belli n, sp, Arctocephalites(?) sp, aff. A.(?) crassum Genus Arcticoceras Arcticoceras harlandi Arcticoceras ishmae Arcticoceras spp. indet. Genus Costacadoceras

"Costacadoceras" sp, indet, A "Costacadoceras" sp, indet, B SUbfamily Cadoceratinae

53

Genus Cadoceras

54 56 56 56

Cadoceras barnstoni Cadoceras sp, Cadoceras variabiZe Cadoceras bodyZevskyi Genus Paracadoceras Paracadoceras sp.

57 57

58 58 58 58 58

Genus et species indet. A Family Kosmoceratidae Subfamily Gowericeratinae Genus KeppZerites KeppZerites sp. aff. K. rosenkrantzi

59 59 59

60 60 60 60

KeppZerites sp. A KeppZerites sp. B KeppZerites(?) sp, C KeppZerites(?) sp. D

Family Sphaeroceratidae Subfamily Eurycephalitinae Genus Iniskinites Iniskinites yukonensis Iniskinites spp, Genus Loucheuxia n, gen. Loucheuxia bartZetti n, sp. Loucheuxia(?) spp.

61 61

62 62 63

64 64 64 64

64 65

65 65 65 65 65

Family Stephanoceratidae Subfamily Cadomitinae Genus Cadomites Cadomites sp, Genus Parareineckeia Parareineckeia sp, Genus et species indet, B Superfamily Haplocerataceae Family Oppeliidae Subfamily Oppeliinae Genus Oxycerites Oxycerites birkeZundi n, sp, Oxycerites sp, Genus Oecotraustes Oecotraustes(?) sp,

65 66

67 67

67 67 67

68 68 68 68

69 69 69 69 69 69

Subfamily Hecticoceratinae Genus Prohecticoceras Prohecticoceras(?) sp, Superfamily Perisphinctaceae Family Perisphinctidae Genus Choffatia Choffatia(?) sp, Suborder Phylloceratina Superfamily Phyllocerataceae Family Phylloceratidae Subfamily Phylloceratinae Genus PhyZZoceras PhyZZoceras sp. aff. P. lcudernatschi

70 70

PhyZZoceras biZZingsi PhyZZoceras sp. aff. P. kunthi Genus AdabofoZoceras AdabofoZoceras(?) sp,

71 71

71 71 71 71 71 72

Subfamily Calliphylloceratinae Genus CaZZiphyZZoceras CaZZiphyZZoceras sp,

Genus HoZcOphyZZoceras HoZcophyZZoceras sp. References

Illustrations 6 7 8

Figures 1. Configuration of marine sedimentary basins and major tectonic features for the Middle Jurassic of Western Canada, showing major paleobiogeographic character of Late Bathonian ammonites. 2. Sedimentary facies belts, location of the Salmon Cache Canyon section (X) and line of cross-section (AB) shown in Figure 3. 3. Southwest-northeast cross-section of Lower and Middle Jurassic rocks along stratigraphic strike. Line of section shown in Figure 2. Bold bar indicates the section described in this report.

D-11 24 24 25 35 35 36 ~4 ~5

'-6 ~8

50

52 55 55 57 59 60

61

61 63 63 66 67 67 68 68 70 71

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4-5

6 9

Graphic illustration of the Salmon Cache Canyon section showing ammonite zones and species distribution. 5. Aerial view of the entire Middle Bathonian to Lower Callovian section at Salmon Cache Canyon. Enlargements of areas indicated are shown in figures 6 and 7. 6. Lower part of section (spathi through ishmae Zones), at north end of exposure. 7. Upper part of section (ishmae through bodylevskyi Zones), at south end of exposure. 8. Septal suture pattern of Arctocephalites spathi n, sp.j figured specimen GSC 68652, from GSC locality 92523; whorl height 2.5 cm. 9. Septal suture pattern of Arctocephalites spathi n, sp.; figured specimen GSC 68267, from GSC locality 92484; whorl height 2.7 cm. 10. Septal suture pattern of Arctocephalites ellipticus Spath(?); figured specimen GSC 68271, from GSC locality 92520; whorl height 2.5 cm. 11. Septal suture pattern of Arctocephalites {rami n, sp.; paratype GSC 68326, from GSC locality 92473; whorl height 3 cm. 12. Badly corroded septal suture pattern of Arctocephalites sp, A; figured specimen GSC 68337, from GSC locality 92520; whorl height 2.5 cm. 13. Septal suture pattern of Arctocephalites sp, B(?); figured specimen GSC 68335, from GSC locality C-95372; whorl height 2.3 cm. 14. Septal suture pattern of Arctocephalites (?) belli n, sp.; holotype GSC 68341, from GSC locality 92564; whorl height 4.2 cm. 15. Septal suture pattern of Arcticoceras harlandi Rawson; figured specimen GSC 68347, from GSC locality 92473; whorl height 3.2 cm. 16. Septal suture pattern of Arcticoceras ishmae (Keyserling); crushed figured specimen GSC 68355, from GSC locality 92564; whorl height 5.2 cm. 17. Septal suture pattern of Cadoceras bamstoni (Meek); figured specimen GSC 68385, from GSC locality 92543; whorl height 2.7 cm. 18. Septal suture pattern of Cadoceras bamstoni (Meek); figured specimen GSC 68387, from GSC locality 92553; whorl height 3.2 cm. 19. Septal suture pattern of Paracadoceras sp.; figured specimen GSC 68408, from GSC locality 92561; whorl height 2.9 cm. 20. Septal suture pattern of Kepplerites sp, aff. K. rosenkrantzi Spath; figured specimen GSC 68419, from GSC locality 92551; whorl height 3.2 cm. 21. Septal suture pattern of Kepplerites(?) sp, C, showing last and penultimate septae; figured specimen GSC 68430 from GSC locality C-95372; whorl height 4.3 cm. 22. Septal suture pattern of Iniskinites sp.j figured specimen GSC 68415, from GSC locality C-95370; whorl height 1.7 cm. Due to extreme approximation, all the sutures cannot be traced satisfactorily; the shaded portion is thought to reflect the actual suture pattern reasonably well. 23. Septal suture pattern of Iniskinites sp.; figured specimen GSC 68411, from GSC locality 92561; whorl height 2 cm. 24. Septal suture pattern of Loucheuria bartletti n. sp.; paratype GSC 68375, from GSC locality 92552; whorl height 4.3 cm. 25. Septal suture pattern of Loucheuria bartletti n, sp.] paratype GSC 68381, from GSC locality C-95375; whorl height 2.7 cm. 26. Septal suture pattern of Oxycerites birkellmdi n, sp.j figured specimen GSC 68434, from GSC locality 92554; whorl height 8.5 cm. 27. Septal suture pattern of Oxycerites sp.j figured specimen GSC 68435, from GSC locality C-95382; whorl height 3.7 cm. 28. Septal suture pattern of Oecotraustes sp.; figured specimen GSC 68431, from GSC locality 92473; whorl height 11 cm. 29. Septal suture pattern of Prohecticoceras(?) sp.; figured specimen GSC 68.433, from GSC locality 92570; whorl height 0.8 cm. 30. Septal suture pattern of Cho{{atia(?) sp.; figured specimen GSC 68439, from GSC locality 92561; whorl height 3 cm. 31. Septal suture pattern of Phylloceras billingsi (Meek); figured specimen GSC 68653, from GSC locality 92553; whorl height 2 cm. 32. Septal suture pattern of Calliphylloceras sp.; figured specimen GSC 68460, from GSC locality 92473; whorl height 4 cm. 4.

Plates Tables 1. Correlation Chart, Middle Bathonian to Lower Callovian ammonite zones in Boreal Realm, and the Northwest European zonation. Double vertical line separating Northwest Europe from other columns indicates intervals of still uncertain correlation. 2. Table of formations, northern Yukon Territory. 3. Chart showing the current placement of Middle Jurassic ammonite zones and their correlations in Western and Arctic North America, East Greenland, and Northwest Europe.

ZONAnON AND CORRELAnON OF MIDDLE BOREAL BATHONIAN TO LOWER CALLOVIAN (JURASSIC) AMMONITES, SALMON CACHE CANYON, PORCUPINE RIVER, NORTHERN YUKON

Abstruct

The Middle Bathonian through Lower Callovian ammonites from the Salmon Cache Canyon section on Porcupine River are dominantly Boreal, represented by an upward succession of Aretoeephalites, Aretieoeeras and Cadoeeras species. They are very similar to equivalent faunas in northern Alaska, East Greenland and northern Siberia, but differ at the species level, so that a new zonation for northern mainland Canada is proposed. In upward succession, the zones are: spathi, poreupinensis, amundseni, (rami, harlandi, ishmae (from East Greenland; restricted), barnstoni, and bodylevskyi. Correlations with the Boreal zonations elsewhere are suggested. Additionally, a small proportion of Pacific and cosmopolitan ammonites in the collections permit further refinement of the correlation of the Boreal with the Pacific and ultimately with the Northwest European standard zonation. The Boreal BathonianCallovian boundary is placed in the interval between the barnstoni and bodylevskyi Zones. One new genus is proposed - Loueheuxia, of subfamily Eurycephalitinae. New species erected are Aretoeephalites spathi, A. poreupinensis, A. praeishmae, A. amundseni, A. (rami, A.(?) belli, Loueheuxia bartletti, and Oxyeerites birkelundi. Keywords:

Bathonian,

Callovian,

ammonites,

Yukon,

Areticoceros,

Arctocephalite8,

Cadoceras,

Kepplerites, LOI.fChuxia, Oxycerites.

Des ammonites d'lige Bathonien moyen au Callovien Inferieur, provenan de la coupe de Salmon Cache Canyon et situee sur la rlviere Porcupine, sont pour la plupart boreales, Elles sont representees par une succession ascendante des especes d'Aretoeephalites, d'Aretieoeeras, et de Cadoeeras. Elles ressemlent beaucoup aux faunes equivalentes localisees en Alaska septentrional, au Groenland oriental et en Siberie septentrionale; cependant, elles se distinguent au niveau espece, ce qui a rnene a l'etablissement d'une nouvelle zonation proposee pour le Canada continental nordique. En succession ascendante, les zones sont less suivantes: spathi, poreupinensis, amundseni, (rami, harlandi, ishmae (du Groenland oriental; restreinte); bamstoni, et bodylevskyi. Des correlations accompagnees de zonations boreales provenant d'ailleurs sont suggerees, De plus, une proportion mineure d'ammonites cosmopolites et due domaine pacifique presente dans Ies collections permet la correlation plus precise entre le domaine boreale et le domaine pacifique, et, en fin de compte, la correlation peut se faire aussi avec la zonation standard de l'Europe du nord-ouest, La frontiere boreale du Bathonien au Callovien se situe dans l'intervalle entre les zones de barnstoni et de bodylevskyi. On propose I'etabllssement d'un nouveau genre, Loucheuria, de la sous-famille Erycephalitinae. Done, les nouvelles especes etablles sont: Aretoeephalites spathi, A. poreupinensis, A.· praieshmae, A. amundseni, A. (rami, A.(?) belli, Loueheuria bartletti, et Oxycerties birkelundi. Mots eMs:

Bathonian,

Callovian.

ammonites.

Keppler1tea. Lou.cfaaio. Oxycerites.

Yukon.

Arctic0cera3.

ArctoeephaIitea.

Cadoceros.

INTRODUCTION

The Boreal Bathonian section at Salmon Cache Canyon on Porcupine River is of interest for two reasons. Firstly, it exposes a succession of closely spaced concretionary layers that are richly fossiliferous, possibly the most biostratigraphically complete single section of its age anywhere in the Boreal Realm, and certainly the most complete section outside of eastern Greenland. The section, therefore, potentially provides a standard succession for the Boreal Bathonian of Arctic North America, and contributes in a major way to the development of an intercontinental Boreal Bathonian standard. Secondly, together with the predominant Boreal ammonite species, there also occur others with southern affinities. Some of these, together with a consideration of the ammonite succession elsewhere, permit some further elaboration of the correlation of the Boreal zonation with that of the circum-Pacific succession and with the Northwest European standard zonation. Unfortunately, these last ammonites belong mainly to genera that are long ranging and are too rare and poorly preserved to identify specifically, so that unequivocal correlations are not yet possible. Unlike most Boreal successions elsewhere, these faunal elements indicate access to Pacific seas to the south (Poulton, in press). Outside of the typical area of Northwest Europe, recognition of the Bathonian-Callovian boundary remains elusive because of the absence of the critical guide fossils due to faunal provincialism. Although this interval is not well exposed in the Salmon Cache Canyon section, the ammonites present contribute to the resolution of this problem indirectly via correlation with East Greenland. Only the Salmon Cache Canyon section and its faunas are described here. There are numerous other occurrences of equivalent faunas (see Poulton, 1978; Poulton et al., 1982), but they are mostly from localities that do not provide a succession of fossiliferous horizons or additional faunal data. They will be dealt with in a later publication. Because of their importance, the ammonite species found in this section are profusely illustrated, in order to document their variation within individual beds where possible, and their range of variation from one bed to another. Description of the ammonite faunas has required the description of many specimens collected as loose material below the section. For some of the less common, non-Boreal species, which are particularly significant forms for correlation southward, loose material is all that is available. Many of the loose specimens can be assigned confidently to the bed from which they came because of their association in a single concretion with a variety of other characteristic fossils, or because the character of the matrix of the concretion allows it to be compared with a particular lithologically distinctive bed in the section.

Fauna! provincialism

Ammonoids, because of their rapid evolution displayed in a complex morphology, their abundance in marine rocks worldwide, and the wide geographic distribution of individual species, remain the principal guide fossils for correlation of Mesozoic marine rocks. Faunal provincialism, however, sets limits to what can be achieved in worldwide correlation. In

2

practice, therefore, the succession of faunas must be recognized in each faunal province independently, and final interprovincial synthesis is achieved by correlation in regions of overlap. To this day, precise correlation of many of the zones of the Arctic Middle Jurassic with those of Northwest Europe and the western part of the Americas has not been achieved (e.g, Callomon, 1958), and a complete zonation for the Middle Jurassic of the circum-Pacific area is still lacking. Furthermore, the faunas present in the Jurassic of many areas, including some in Northern and Western Canada, are still undescribed, and the succession in some critical areas remains poorly documented. The fact that marine Jurassic faunas exhibit provincialism was discussed extensively first by Neumayr (1883), with regard to the Upper Jurassic of Europe. He also expressed the basic principal that underlies provincialism, and gave some interpretations of its causes. That distinct faunal provinces in the Jurassic existed as far back as Bajocian time was recognized by Arkell (1956), who simplified distribution patterns into three faunal realms Tethyan, Pacific and Boreal, Imlay (1965) discussed the evidence for, and application of, the fauna1 realms to North America in particular. The literature on Mesozoic marine faunal provincialism is large and is not reviewed here (see Jeletzky, 1971 for such a discussion), and hypotheses regarding its causes are many. Some amount of latitudinal climatic differentiation, together with restricted patterns of circulation in marine basins, in large part due to the interference by continental masses, seem to be widely accepted and sufficient causes for the distribution patterns as we see them. With increasing knowledge of ammonite distributions arising from continued taxonomic work around the globe, it is apparent that neither their biogeographic patterns nor the biostratigraphy are as well understood or as clearcut as has been thought, even in Europe (e.g, Ziegler, 1980). For example, the abundance of phylloceratids and the presence of Cadomites in the mainly Boreal faunas described in this report is surprising, and indicates the premature character of generalizations regarding Jurassic ammonite distributions in the western Americas. Faunal provincialism has made correlation of the European type Bathonian successions with those outside Europe difficult. Only recently have Bathonian rocks and fossils been widely recognized outside of Northwest Europe. The greatest advances were first made in the Arctic Atlantic areas, principally East Greenland. Among the first of the Arctic species to be described was Ammonites ishmae Keyserling (now Arcticoceras), found in an isolated position in northern European Russia Its similarity to European (Keyserling, 1846). MacrocephaIites led early workers to conclude that it was of Callovian age (the Callovian was, at that time, included in the Upper Jurassic), Other species that were ascribed to the Middle Jurassic could not be matched exactly with those of Europe, and a number of new names were introduced. Some were compared with A. ishmae of northern Russia. Given European generic identifications, collections over wide areas of the Arctic were dated as Callovian, Finally, it was recognized by Spath (1928, 1932) that the Arctic ammonites represented new genera - Arcticoceras, Arctocephalites, and Cranocephalites - that are entirely unknown in the classical areas of Europe. Spath (1932) dated these Arctic genera as Late Bathonian and Early Callovian, mainly on the strength of their general similarities and supposed phylogenetic relationship to the Indo-European Macrocephalitidae, at that time believed to range into the Bathonian more extensively than is currently thought.

Arkell (1956) recognized a widespread Batnonian -egressreo and subsequent Callovian tra nsgr ession over much )f Europe and t he ctrcwn- Te t hys region. Misled by the "l'lainly Callovi an datings of fa lSlas fr om the Arc t ic and 1,'estern Nor th Ame ric a, he concluded e rroneousl y that the 3a t honian reg ressive e pisode was worl dwide . This conclusion -einf crced t he CaHo vian and Late Bathonian da ting of fa .....as on North Ame rica an d USSR which bcee no relation to those of Eur ope , but which did resemble t hose of East Greenland. Callomon (1959. 1975; CaJlomon and Birkelund, 1980) erected the c ur re nt Boreal zo na tion fo r East Gre en la nd (see Tables I, 3). He proposed a Bathonlan age fo r CadocenJ.! ca!y:r a nd other fa unas as old as t he oldest Cra nocephoUtes seect ee, C. borealls. In o rder t o emphasi ze t he differences MId the difficulty of correlating between the typical and t he boreal successi c ns, he proposed t he te r m 'Bore al Bathonian' for the latter.

The fi rst Ju ras sic fossils that probably came from t he Imon Ca c he loca li t y were discovered in t he possession of dso n's Bay Com pany c hie f factor, Mr. Geo rge Barnston, by Y. Hind, leader of the Assi niboi ne and Saskatchewan ploring Expedition of t he Nort hwest Te rr itory. under t ru c tion fr om th e provincia l secretary of Cana da. The ogle sa mple co ntai ned two species of a mmoni te, both of ic h were described as new by F. B. Meek (859), who ,sta ke nly thought them to be C re t aceous, a lthough he ognized thei r J urassic affinities. 1ne sample was esum ed to have been carried to t he trading post in c kenzie River vall ey by t rappers.

The next Juras sic fos sils fr om t his locality were lected al ong Por cupine River by R.G. Mc

ISHMAE

Arcllcoceras Ishmae (1)

ArcIIcoceras ishmae

ArcIicocIns cf. or all. A. ishmae. Arclicoclns michaelis, _sp.inelet.

AncIIcoceras ef.ishRNM (?) AncIIcoceras Ishmae,

A. cf. axcent1icum ArcIIcocerashai1lJndi, HARLANDI

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Porcupinensis Zone (Beds 15-25)

Frami Zone (Beds 46-47)

Several similar species are approximately equally abundant in this zone. Arctocephalites porcupinensis n, sp, is the most conspicuous in some beds in the the lower part, but was not seen in the lowest beds. The lowest appearance of the entire suite of species in Bed 15 is taken to mark the base of the zone. These include A. callomoni Frebold, A. spp, A and B aft. A. nudus Spath, A. sp. A aff. A. sphaericus Spath, A. arcticus (Whitfield) - appearing only in the uppermost part of the zone - and Arctocephalites(?) sp. aft. A.(?) crassum (Madsen), Thus, most specimens are still small and moderately compressed, although there is an increasing proportion of inflated forms. The lowest appearance of Phylloceras sp. aff. P. kunthi Neumayr, of Genus Calliphylloceras, and possibly also of Genus Iniskinites (represented by a single small undeterminable fragment that is now lost) is in this zone.

This fauna is dominated by Arctocephalites [rami n, sp., the lowest occurrence of which in Bed lt6 defines the base of the zone. Additionally, Arctocephalites(?) belli n, sp., Phylloceras sp, aft. P. kudernatschi (von Hauer), and Calliphylloceras sp. occur, and the lowest occurrence of Arcticoceras, that is, A. sp. indet, is in this interval.

The lower part of this interval is that characterized by

Unnamed Zone (Bed 48)

This fauna is represented by only one fossiliferous bed, containing a unique assemblage of Arctocephalites(?) sp, E, and genus et species indet. A.

"Arctocephalites sp", in preliminary reports (Poulton and

Callomon, 1976; Poulton, 1978).

Harlandi Zone (Bed 53) Amundseni Zone (Beds 26-45)

The lowest bed is characterized by the appearance of the largest species, Arctocephalites amundseni n, sp., in a fauna that is otherwise similar to that below, with mostly smaller species. Other elements of the lower part of this zone are A. arcticus (Whitfield), A. porcupinensis n. sp., A. sp. A aft. A. nudus Spath, A. praeishmae n, sp., A. sp, D, Arctocephalites(?) sp. aft. A.(?) crassum (Madsen), A.(?) freboldi (Spath), and Phylloceras sp, aft. P. kunthi Neumayr.

This fauna, known from only one fossiliferous bed, contains Arcticoceras harlandi Rawson, Cadomites sp., Arctocephalites(?) sp, aft. A.(?) freboldi (Spath), and other Arctocephalites sp, indet., represented by small, smooth body chambers having apertural constrictions and cross-sections similar to those of A. harlandi shown in Plate 19 (figs. 7, 8). This interval is that characterized by "Arctocephalites sp. cf. greenlandicus" in preliminary reports (Poulton and Callomon, 1976; Poulton, 1978).

Higher beds are characterized by a mixture of species Arctocephalites porcupinensis(?), A. spp, aff. A. arcticus and A. callomoni, A. praeishmae, A. sp. B, and, possibly, A. sp, A. Arctocephalites kigilakhensis Voronetz becomes

increasingly abundant upward so that an upper Kigilakhensis Subzone, in which A. kigilakhensis and A. praeishmae are most conspicuous and A. amundseni is rare or absent, can be distinguished. Phylloceras sp, aff. P. kudernatschi (von Hauer) first appears in the upper part of this interval. Arctocephalites sp.

B aft. A. sphaericus Spath, one specimen of which was found in loose material with Phylloceras sp, aft. P. kudernatschi (GSC locality 925lt6) is thought to also be present in the amundseni Zone. The interval comprising the amundseni and frami Zones is that characterized by "Arctocephalites greenlandicus" in preliminary reports (Poulton and Callomon, 1976; Poulton, 1978).

12

lshmae Zone (Beds 55-60)

by

The zone is represented, in three fossiliferous horizons, (Keyserling), A. ishmae(?), and

Arcticoceras ishmae Kepplerites(?) sp. D.

These beds have contributed many distinctive, hard, dark red, dense concretions to the talus below the section, some of which are richly fossiliferous and document the following forms in this zone (each GSC locality number, except C-95372, represents a single concretion, so that there is no doubt of the association).

GSC loco 92552:

Loucheuria bartletti n, sp, Iniskinites sp, Phylloceras billingsi (Meek)

GSC loco 92554:

Arcticoceras ishmae (Keyserling) O:rycerites birkellmdi n, sp. Loucheuria bartletti n, sp. lniskinites sp.

GSC loco 92564:

Additionally, a rich fauna is documented in distinctive, yellow-weathering concretions that occur abundantly in the talus below the section. Each number records the association in a single concretion: GSC loco 92553:

Arcticoceras ishmae (KeyserlingX?) Arctocephalites(?) belU n, sp, Choffatia(?) sp, Phylloceras billingsi (Meek)

Cadoceras barnstoni (Meek) Cadoceras variabile Spath Arcticoceras(?) sp, lniskinites(?) sp, Phylloceras billingsi (Meek)

GSC loco 92473x:

Loucheuria bartletti n, sp. Phylloceras sp, aff. P. kudematschi (von Hauer)

GSC loco C-95354:

Arcticoceras ishmae (Keyserling) O:rycerites birkelundi n, sp.

GSC loco 92568:

Cadoceras barnstoni (Meek) Cadoceras sp, Phylloceras bilUngsi (Meek)

GSC loco C-95372:

(the following species occur together in a single concretion; the concretion also contains other material):

GSC lac. C-95370:

Cadoceras barnstoni (Meek) lniskinites sp. Phylloceras billingsi (Meek) Phylloceras sp, aff. P. kudematschi (von

Arcticoceras ishmae (Keyserhng) Orycerites birkelundi n, sp, Choffatia(?) sp.

GSC loco C-95374:

GSC loco C-95382:

Arcticoceras(?) sp. O:rycerites sp. Loucheuria bartletti n, sp. Arcticoceras sp. indet, O:rycerites sp,

Hauer) GSC loco C-95381: Loucheuria(?) sp, Phylloceras billingsi (Meek)

GSC loco C-95383: Loucheu.ria(?) sp, Phylloceras sp. Calliphylloceras sp, Kepplerites sp, A, found loose in the talus, probably also comes from this bed.

The presence of Orycerites in this zone represents its lowest, and apparently only, occurrence in the section, and that of P. billingsi represents the first appearance of that species. Other forms that were found loose but that probably come from this zone include Parareineckeia sp., Adabofoloceras(?) sp., gen. et sp, indet, B, and possibly also Arctocephalites sp. A(?) (University of Alberta loco 45413). Furthermore, J.H. Callomon (pers, comm., 1975), while in the field, tentatively identified Siemiradzkia sp. and Oecotraustes sp. in loose material that he thought came from this zone but these identifications could not be confirmed by detailed studies of the collections by the writer.

Umamed ZcIne (Bed 66)

No ammonites are positively identified in the material presently available for detailed study (GSC loco 92470). J.H. Callomon tentatively identified Paracadoceras at this level while in the field. This genus is sparsely represented in the talus below the section but is not associated with other ammonites.

Bamstoni Zone (Bed 62)

JJcJd)UvsIc)i ZcIne (Bed 61)

fauna, characterized above all by Cadoceras (Meek) and Phylloceras billingsi (Meek), also contains in place Cadoceras sp., lniskinites sp., and the lowest Kepplerites, K. sp, aff. K. rosenkrantzi Spath and This

barnstoni K. sp. B.

This fauna contains only Cadoceras bodylevskyi Frebold. This is the interval characterized by C. septentrionale Frebold in preliminary reports (Poulton and Callomon, 1976; Poulton, 1978).

13

DESCRIPTION OF THE SEC TION Section PU- 3-75, 81. Salmon C ache Canyon, POF'CUlXne Rive r, no rthern Yukon. Bluffs a re found on the west bank, just south of the ma jor bend where th e river c ha nges c ourse fro m f'IOl"th to wes t; Iat, 67-25 to 26'S , long. I 37-46'30"W. The section was described and measured, and t he fossils collected by T.P. Poulton and J .H. Ca llomon in 197.5; a nd by T. P. Poul ton, J .H. Callomon, T. Birke lund, R.L. Derre rman, and D.H. Mc Neil in 1981. The co llections and generalized descript ion of l.A. Jeletzky (in Frebo ld, 1961, p. 2) have been Iece r pcea te d. The section , with preliminary fos sil ident ifica tions, has prev ious ly been ilIusua tedby Poulton and Cal lo mo n 0976, p. 348, c o l. 5) and Poul to n (1978, PI. 11, fig . 2; the coo rdinates given t here are inco rrect), and it ap~ars in Figures 4 to 7 of t his report.

Much of t he s lope is obscured by talus, a nd t he sect ion was piece d t oge t her from a study of various outcro ps. Mar ker-beds ar e, howeve r, prom inen t, pers istent and ch ar ac teris tic, leaving the succ ession in no do ubt . The lo wer beds (1-20), a re best exposed at t he nor thernmost end of the bluff . Beds 22 to 40 form a pr o minent and well expose d, re gularly ba nde d se ries so me 100 to 200 m farthe r sout h, bounded by t he most southerly of three gullies beyond which t he s lopes are he avily obscu red by talus, The northernmost of t he three gUllies gives a cle ar section up to and inc ludi ng th e prominen t marke r iron st one, Bed 5&, at t he top of t he c liff , jus t under t he t re es. This is th e highest bed e xposed any whe re along t he nor thern ha lf of t he c liff . The re maining part o f t he section, Beds 59 to 68, is exposed intermit tently in a pecmlnerrt g Ully some 200 m f rom t he so uthern e nd of the cliff. This gully widens and becomes t ree cov e red just under th e highest point of t he cliff . Different par ts of the section we re exposed in 1975 and 1981, which permit ted t he filling of gaps, c orrec tion of errors, and add ition of greate r detail in th e second year. The different exposure in 1981 was due in part to heavy slumping fol lo.....ing a forest f ire th a t occurred between 1975 and 1981. The section belongs to t he Richardson Mountains Forma t ion (Poulton e t ar., 1982) of the Bug C reek Grou p, in an unt ypically fossili fe rous an d ferruginous ractes, The upper saodstcees (Units 68a-er:,""a1

Those Salm on Cache C anyon specime ns wit h a hi gher ...-bcr t heigh t appear to agre e in most respects with t he ho lot)' pe of C. mriabile Spath (1932, PI. XIX , fig . I ). The adult cross- sect ion of tha t hclct ype is not clear from Spath's figu re l a an d was no t f igur e d specifically so t ha t t he SlJbquadr a t e adult fr agm en ts taken t o re prese nt the same species in nor th ern Yuko n c an not be co nfi r me d in the bcl c rype, As a lread y st a t ed by Spath (I'H 2, p. 76), the lar ger sped men he figur ed (P I. XVIIL fi g. la) has a nar rower , s teeper - .... a ned um bil icus, approachi ng t hat of A rcticoce ros, and may not represent t he same species, so t ha t t he a dult cross-section o f t be spe ci men he f igured cannot be taken to t e p-esent t hat o f C. mriabile. The whor l he igh t becomes lower and t f-e um bilicus slightl y mor e open in ieter gro wth stages of the Porcupine River specimens assig ned to C.ool'Tl.'ltoni . In con t r ast, one (PI. 27, fig. I ) re t a ins a high whorl height to a lar ge dia meter, and shows ve nt ral weakenin g of the r ib bing . as in t he hclctype of C. m ria bile, t o which species it is a ssigned.

Sim ilarly, t he no r thern Yukon speci me ns with a high er .....·horl he ig ht ar~ no t eaaily d istingUis hed fr om t he fig ured t ypes o f C. subcatO!lt oma vcecoet z 11 962, PI. XXIV, f ig. I; PI. XX\'. fig . O. Besides t he close mor phological sim ilarity of t hese t tv e e species. t he ir s)nonymy is further sugge s t ed by t he ir CO- OCCUlTen ce in Eas t Gr eenland. Another nort hern Siberian species . C. Subca l}T vcronet z , is also ver y similar, if

"

not identical. These two Siberian species appear to differ from C. barnstoni only in having coarse ribs persist to a larger growth stage. C. sUbcalyx also is thought to eo-occur with C. variabile and C. cf./afL barnstoni in East Greenland although it occurs in association with other Cadoceras species in Siberia that are of younger aspect. Adult specimens of C. barnstoni and one juvenile at least (PI. 28, figs. 7, 8) have a flattened venter, indicating that C. ventroplanum Voronetz is probably also a form of this species. Its precise stratigraphic position and associations in northern Siberia are not documented, but it is another of the forms identified in the variabile beds of East Greenland. No significant difference is seen between C. barnstoni and C. laptievi Bodylevsky, but the assumed rather than proven stratigraphic age of C. laptievi renders its synonymy also unproven. If Bodylevsky (1960) were correct in stating that C. laptievi is among the oldest Cadoceras, then it is probably a junior synonym of C. barnstoni, to both of which species the subgeneric name Catacadoceras Bodylevsky (1960) applies.

Cadoceras bodylevskyi Frebold

Plate 26, figure 12; Plate 27, figures 2-6; Plate 28, figures 1-9 bodylevskyi Frebold, 1964, p. 10, 11, PI. XVII, fig. la-c, PI. XIX, figs. 1, 2. Cadoceras septentrionale Frebold. Poulton and Callomon, 1976, Fig. 61.3; Poulton, 1978, Fig. 2.

Cadoceras

Material and occurrence.

Many specimens, including two nearly complete ones (figured specimens GSC 68402, 68405) from GSC locality 92544 (Bed 68c) and possibly others from GSC locality 92467, presumably derived from Bed 68C; 15 specimens (including figured specimens GSC 68401, 68403, 68404, and 68406) from GSC locality C-95367 (Bed 68c); many poorly preserved specimens from GSC locality C-95384 (Bed 68a). Bodylevskyi Zone. Other specimens occur loose below the section, although their fragile character makes them rare and fragmentary. The collection from GSC locality C-95367 contains a few, large, relatively globose specimens that are most similar to the specimens from GSC locality 92544, which are more typical species. These are described first below. Others are smooth and apparently adult at a much smaller diameter, and more compressed. Still other specimens are intermediate in size, at what probably is their adult stage, judging by the extent of their last (smooth) growth stage. One large specimen has relatively compressed inner whorls. All these specimens from a single bed are therefore taken to represent a single, widely variable species.

Description.

Cadoceras sp.

Plate 26, figures 9-11 One fragment (figured specimen GSC 68399), found loose below the section (GSC loco 92520) in a rock type indicating its source in Bed 62, has poorly preserved inner whorls that appear to be similar to those of C. barnstoni, and an outer whorl that is strongly acuminate. It is much wider than high, with steep umbilical walls, a rounded but relatively abrupt umbilical edge, and weak, irregular ribs that are very slightly projected forward on the internal mould.

The shell of the large specimens is ribbed to a diameter of about 77 mm, the ribs fading out gradually over the space of a whorl length. This occurs near the beginning of the body chamber of the adult shell. The primary ribs, on the upper part of the umbilical wall, are straight, and essentially radial. Each primary rib bifurcates at a node at the umbilical margin, and there is some intercalation of secondaries. The first half of the body chamber is smooth except for the umbilical nodes, which continue to the aperture.

Cadoceras variabile Spath

Plate 27, figure 1 Cadoceras variabile Spath, 1932, p, 75, PI. XIX, fig. la-d. ?Cadoceras crassum Madsen. Frebold, 1961, p. 17, PI. XIV, fig. 2, Pl. XVII, fig. 1. ?Cadoceras sp. indet. Frebold, 1961, p. 21, PI. XIX, fig. la, b. Cadoceras variabile Spath, Voronetz, 1962, PI. 20, fig. 3.

Two partial specimens (figured specimen GSC 68400 and another figured by Frebold, 1961, PI. XVII, fig. 1) found loose below the section (GSC locs. 92561, 35692), the first in a rock type indicating its source in Bed 62, differ from C. barnstoni (Meek) in high whorl height, ribs that fade out ventrally and adorally, narrow umbilicus and rounded umbilical edge even at large diameter. They thus closely resemble the holotype of C. variabile Spath. Other, similar juvenile specimens collected in Bed 62, or almost certainly derived from it, have been discussed under C. barnstoni from which this species cannot, apparently, be distinguished, at small to intermediate growth stages. The specimen figured here closely resembles one figured by Callomon and Birkelund (1980, PI. 1, fig. la, b) as Arcticoceras/Cadoceras sp. nov.? aff. variabile Spath, Discussion.

56

The secondaries are inclined very slightly forward but pass over the venter without projection. Fine, distinct, secondary ribbing and coarsely spaced but weak and irregularly spaced corrugation appear on the oralmost half of the body whorl. The body chamber appears to be a full whorl in length. The umbilicus is deep and conical. The whorls embrace each other more strongly in the last growth stages and the umbilical walls of the outer whorl are nearly perpendicular. The cross-section is wider than high at all growth stages seen, Le, at whorl heights greater than 18 mm. There is considerable variation in the degree of arching (compare figures 1 and 5 of Plate 28). The suture line cannot be traced in any of specimens available.

the

Two of the loose specimens from GSC locality 92467, although probably derived from Bed 68c, have a more open umbilicus, which retains its width in the last whorls seen. One extreme specimen (PI. 27, figs. 2, 3) becomes smooth, except for umbilical nodes, at a whorl height of about 3 cm, corresponding to a diameter of about 6 cm. The ribs are essentially as descr ibec above. Irregular

c orr uga ti ons a ppe ar near t be adora l end o f the s pecimen , t he las t of w hich is most pt"ooounced an d may poss ibly repre se nt an e per-t cr el c ons t r ic tion. Howeve r , t he specimen is not entir e and the end o f septee c annot be seen, so t hat there may have bee n mor e body chamber t han is now pre ser ve d. It is taken to be adult because of the exte nsive smooth pa rt. It is quite st ron g ly arched, c om pa red t o t he specimens des c r ibed above.

s tages. The juvenile is s t ron gly r ibbed, t he r ibs gradually fading on the ve ntra l parts firs t, an d the body cham ber is smooth. TIle adult, and t he stage a t which r ibbin g fades, is smal l. The st rong diff erence in ribbing character an d whorl cross-section separ a t es t he no r thern Yukon specimens f rom those o f more t ypical Ca doC1"l'Os, re pre sente d by C. subl aew (Sower by). Paracado cera s Canyo n.

IS

sparsely re present ed at Sa lmo n C ache

Another specimen (PI. 28, figs . 3- .5) becomes smoo t h a t a somewhat la rger g ro wth stage and sho ws a co nside rable decrease in ar c hing in the la st par t preserve d. Still an o t he r (P I. 28, fi gs. I, 2) rema ins ri bbed to a sim il ar , relat i ve ly large grow t h s tage , bu t re mains st rong ly arched. Tbe re is, a ddition a ll y, some variation in the deg ree of archi ng from one gr ow t h sta ge to ano ther within individual specimens. All these eo-occur ring for ms are t hus in termediate between t he t wo ex ternes - t be large and depressed forms (PI. 27, fig s. 4-6), an d t he sm all, mor e strongly arched forms (PI. 27, fi gs. 2, 3). Therefore, t he y are all t a ken t o repre sen t on e species. The presence o f so man y int e rmedia t e for ms wo uld suggest th a t wide morp hol ogic a l va r iat ion, rather t ha n se xual dimor phism , is t he case.

,\l a t e ria l and occur re nc e. Two fr a gment ar y specimens (figIXed specimens GSC 68407, 68408) found loose in a boulder (GSC loc. 92.561) t ogether wi t h cccc ce-ee barnst oni (Meek)(?) and Phylloce ros bllUngsi (Me e k), indicat ing de rivation fro m Bed 62; one spe ci men (figu red specime n GSC 68409) found loose toget he r wi t h Phylloceras billingsi (GSC tee. C-95372). Barnstoni Zon e .

Dis cussion. The species co nf orms wi t h C. bocI')'le \is kyi Frebold (19 64, PI. XVII) from Axe l Hei berg Island , in its c ross-sect ion, pe rsiste nce of r ibbing , e xt re me steepening of um bilical walls in t he last grow th stages o f the la rge specimens, and t he show of umbilical nodes in t he e arly whor ls in t he um bilicus. The ri bs are we a ker in t he present specime ns, ho we ve r, and t hose fr om GSC locality 92467 have a wider um bil ic us in t he la st gro wth st a ge s.

Description. Part of an int e rm edia t e whor l a bout 2 t o 2.3 cm high is seen on one fragme nt (PI. 29, fig. 61. It has strong. pr orsiradiate r ibs. .\l os t o f them bifurca t e a bout half way up the flank , wher e t~ pri mary ribs are sligh tly swollen; som e r ibs are undivided. TIle ri bs are fi ne , s tand high, an d are swollen into bull ae low on t he fl an k. The flank and venter appear t o be s moo t hl y r oun de d; t he umbilical edge cannot be seen.

Of o t he r Ca nadi a n specie s de sc ribed , t his species is ve ry close t o C. septentrionale Frebold (1964) . Howe ver, r ibbing pe rsists fur ther on t he large specime ns, and t he umbilica l ma r gi n is sha rper than in C. septentriona le . The um bilica l nodes are stron ger on t he body whor l.

The outer, nonseptete whorl of t he same speci men (P I. 29. fi g. 5) is smoot h ex cept f or shor t , swoll en , prorsiradia t e pr imar ies, and ver y weak s uggest ions of secondarie s over the venter (int ernal mould o nly). The c r os ssec tion is high , smoo th ly rou nde d with slight ly fla ttened r ibs, and has a fairl y a brupt um bilical edge. The umbilical wal l is high , smooth, and s t e ep t o vert ic al.

The strong umbilical nodes se par a te t his species from C. vorone tsa e Fre bold ((964), a s we ll as f rom C. sublaew Sowerby, and C. emelianze vi Voronetz. Cedoce res a rcticum Fre bold (1964) ha s more gent ly sloping u mb ilical walls, an d less pronounced umbilical nodes in lar ge grow th s tages.

Cadoceras elatmoe (Niklttn, 1881, p. 116, PI. XJ(lV), figs. 20- 23; vceoneta, 1962, PI. XII, fi g. la , b; PI. XXVI, fig. la , b; Mele dina, 1977, p, 70, PI. 13; PI. 14, fig . I; P I. IS, t lg. 2; PI. 16, fi g. I ; PI. 17, fi g. 1; PI. 20, fig . I) f ro m Russ ia, '.l.. hich is pro bab ly o f about t he same age as C. bod'yle vskyl' of ace t hem Yu kon , judgi ng by i ts stratigra phic rel a t ion in Sibe ria (see, for e xample, Meledina , 1977), is similar , but has a wider umbilicus.

Pcracccccem s sp. P late 29, figu res 1- 6

An associa ted fra gmen t (PI. 29, fi gs. 3, fJ) is similal'" but is more depressed, and has a spi ral sw e lling a long t he locus wher e the pr imaries disappear ventral ty, Both t hes e characters may be due t o tect on ic distor tion. The su t ure line is shown in F igure 19. The first lateral sad d le is deeply and somewha t as ymmet r ically dis sected, as in c cccce-cs barnstoni (Me e k).

Ge nus Parocodoceras Crickmay, 1930 The t ype specimen, P. harw yi C r ic kmay , is poo r ly oeese-ved and is hardly su ff ici e nt for a generic diagnosis (see also C al lomon, 1984). Its s ta t us must re main uncer tai n until ce rt er t o pc r ypic materia l is a va ila ble. Howe ver, certai n -ietertat from MOlSld t he Arctic has a ch aracteristic "'"1 or phology and t he name has been widely applied t o these c.su rcnve forms. TIley are mode rately evolute and - c-npeessed in the ju venile stages but som ew ha t infl at ed , and ~ : J I re la t ive ly e vol ut e in int ermedi a te and lat e grO\1.·th

19. Septa l su t we p:lttem of ParocadOcerus .$po; f igured s pe ci men GSC 68408, from GSC l ocalit y 92.56J; \I-'ho ri height 2.9 c m.

Yf~

l7

One other fragment (Pl. 29, figs. 1, 2) has swollen primaries and weak secondaries that are nearly effaced over the venter. The umbilical edge is abruptly rounded, the umbilical wall steep or vertical and high.

Genus et species indet, A Plate 32, figures 2, 3 and occurrence. One incomplete and poorly preserved specimen (figured specimen GSC 68367) from GSC locality C-95364 (Bed 48).

Material

Spa,- _73:. c, i.)i ::>_,:- -,e-:: a succession of three different c.sse-:L":~ :X Keq:i£>---:!es in Northwest Europe. The differences .: :e:::-~ iiI"lC ocs, :_~-, of tuberculation of the young grown s:a~e.- a;-c t"le ce~~ee :0 which a runcinate venter persists (as ~e-:x::e:: :-' Se.a:- 1. eo not appear to hold well in the Bor e a, >-,::::eSSi.:Y' .r ::'a;s: Greenland, where they are best known. 5-;)..... e :: :-e.- .~e described earlier by Ravn (1911), Sokoi ov a-: ~:-::..e', s,,~. ([ 931), Spath (1932), Donovan (1953), and ot:-:e~s .- x,-e cet ail. The criteria for specific differentiation i:lCLCe : -e ce zr ee and persistence of tuberculation and runcinat.c- 0: :-e ·'.-e"1ter, the degree of inflation, the coarseness anc :e~s.:\ :: ribbing, and the size. The present material is neither s.:::.c.e"1'ly abundant nor well enough preserved to contribute sigr:l:.:antly to the knowledge of the biostratigraphy or affinities 0: Kepplerites.

At a whorl height of about 1.5 cm, the shell has fine, finely spaced, smoothly forward-curved ribs that bifurcate regularly one third to one half of the way up the flank and which pass over the venter with considerable forward projection. Smaller growth stages cannot be seen.

Description.

Kepplerites sp, aff. K. rosenkrantzi Spath

Plate 30, figures 1-10, 16 aff. Kepplerites rosenkrantzi Spath, 1932

The shell gradually becomes smooth at a whorl height of about 2.5 cm. The shell is still septate at this stage. No body chamber is preserved. The cross-section is compressed and markedly acuminate, widest around the umbilical edge. The umbilicus is small, steep-sided, with a rounded but relatively abrupt edge. The forward projection of the ribs, acuminate venter, and strongly compressed cross-section, ally this form with slightly younger Arcticoceras. The fine ribbing, its orientation, and the shell shape are all closely similar to inner whorls of specimens from Svalbard identified as Arcticoceras harlandi Rawson (1982). That species occurs at Salmon Cache Canyon above the present specimen, which is not sufficiently well preserved to identify precisely, although the two are clearly closely related. This may well be the inner whorls of associated A.(?) sp. E or another closely related species. Parachondroceras Imlay (1967) is also similar, but the single, poorly preserved specimen does not warrant detailed comparison with this significantly older genus. Discussion.

Family KOSMOCERA TIDAE Haug, 1887 The family is represented by a few specimens of several different morphotypes of Kepplerites.

Subfamily GOWERICERATINAE Buckman, 1926

and occurrence. Two well preserved but fragmentary specimens (figured specimens GSC 68422, 68423) from GSC locality 92543 (Bed 62), one (figured specimen GSC 68420) from GSC locality C-86389, and three (including figured specimens GSC 68419 and 68421) from GSC locality 92551 (loose below section). Associated ammonites in Bed 62 include Cadoceras barnstoni (barnstoni Zone). The lithology and fossil content of the matrix associated with the best preserved loose specimens (GSC loco 92551) indicate this bed to be the source.

Material

The best specimen collected in place in Bed 62 has reasonably well preserved juvenile whorls (PI. 30, figs. 8-10). From a whorl height of 5 mm (diameter about 14 mm) up to a whorl height of 11 mm (diameter about 24 mm) there is a lateral row of strong nodes slightly below halfway up the flank, which are loci of bifurcation of the ribs. Two rows of weaker nodes lie along the juncture of the flat venter and the flanks. The primary ribs are inclined gently forward, and the secondaries are nearly rectiradiate. The ribbing is relatively coarse.

Description.

At a whorl height of 13 mm, the umbilical wall becomes steeper, and the lateral nodes at the points of bifurcation are low on the flank. At larger growth stages, this characteristic is further developed, so that the umbilicus is deep. The small whorls are about as high as they are wide and are nearly circular in cross-section, except for the flat venter. The umbilical wall becomes steeper with growth, and the lower part of the cross-section of the larger shell is subquadrate; the ventral part is unknown. Overlap of whorls is along the line of lateral nodes, and coiling becomes increasingly involute with growth.

Genus Kepplerites Neumayr and Uhlig, 1892 Kepplerites and closely similar genera of the family Kosmoceratidae have been described from Late Bathonian and Callovian deposits of northwest Europe, Spitzbergen, the Trans-Caucasus area and North America, with spotty occurrences elsewhere. An extensive literature exists concerning the succession and relationships of Kepplerites and related forms, much of which is summarized by Spath (1932) and Arkell et al. (1957).

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Another specimen from GSC locality 92543 (PI. 30, fig. 16) has strong ventrolateral nodes at a small growth stage. One found loose (PI. 30, figs. 4, 5) has weakly developed lateral nodes at a whorl height of 3.5 cm (this may be due to abrasion), and flatter flanks than the other specimens, imparting an even more subquadrate crosssection. The best specimen comes from talus below the section

(PI. 30, figs. 1-3). The description above applies except for

t he follow ing fe w differen ce s. Even a t gro wth stages below a whorl hei ght of 9 mm, t he pri maries a nd secondaries a re both inclined for wa rd mor e st ro ngly . The y are fi ne r and more cl osel y spaced. The la t e ral nodes a re wea ker . The specimen is septate to a whor l heigh t of 38 mm . The suture pattern, a t a whor l height of 3.2 cm, is shown in Figure 20.

DiscwsiOfl. The specimen is no t sufficiently well pre se rved t o identify or describe in detail. The r ibb ing at the intermedia t e and in t he largest (noos epta t e ) grow t h stage is coarser t han in Kepplerites sp, att, K. rosenkralltzi desceibed abo ve , or in any other species described by Spath (J932) fro m East Greenland . Add itionally, t he c ross- sect ion is lowe r , and is sm oo t hly rou nded, not subquadra t e ,

Ke PJ-!eri t es sp , B P late 30, figures 17-2 1 Ma te ria l 0Tld occurrence . One sm al l fra gment (fi gured specimen GSC 68 425) from GSC lo cality 925 43 (Bed 62) a nd ano ther (figu red specimen GSC 68426) found loose be low t he section (GSC ice. C - 9 H 72). The for me r is in the bamstonl Zone , an d the latter ma y well ha ve been der ived fr om t he re also. Figure 20. Se pt a l suture pattern of Kepple rites sp. o ff. K. ros enkmntz l Spath; f igu red spe ci men GSC 68 419, from GSC locallty 9255J; whorl height 3.2 c m. Anothe r sm all specimen found loose (P I. 30, figs . 6, 7) shows t he s t ron g lateral and double ven t r al r ow of nodes in t he juvenile stage, and t he dose spacing of t he two ven tral rows. Because t he la t e ral r ow of nodes is st rong ly de ve loped and lies high on t he fl ank , t he cross-section is much wider t ban high at a diameter o f about 1I cm. DisCUMfon. Although all t he species o f t he East Greenland socceesieo a re not ye t described, and t he specimens present in t he Porcupine R iver section are no t complete, t he y seem t o c cn f oem best wi th Spa th's (19 32, p.89 , 90) descript ion of K. rosenkrontzi . The charac ters in common, which also dist inguish these specimens fr om other described species, incl ude t he well devel oped la t e ral row of tu bercles and t he runci nate ven ter in t he earl y stages, and the re lative ly low, mor e rounded , som e wha t infla ted cross- sect ion o f the ad ult , as illustr a t e d by Spa t h (19 32, P I. XXVI, fig . n, The nort hern Yukon specime ns differ fr om the East Greenlan d ones, however , in the slightly g reater si ze to which the r unci na t e vente r pe rs ists, and in t he corr espondingly somewhat steeper f lanks and st eepe r umbilical wal l of the in t e r med ia t e whorls. The seconda r y r ibs of the you ng growth stage in the nort hern Yukon s pecime ns differ f rom th ose of most ot her de scribed speci es in that there are tw ice as man y of the m as there are pr imar ie s , an d in the ir c oa rse spacing . Ho we ve r, t he early stages o f most descr ibed Kepplerites hav e no t been fig ured by prev ious workers, so a deta iled compari son cannot be made . The early s t age of Tufcelli t es appro.rfmatw Buckman ( 9 )), PI. CCCXXXVn are ve ry similar to those of t he northe rn Yukon specimens, a lthough t he runci nate venter does no t persist t o as la rge a siz e and t he adult shell differs in t he style of coiling, r ibbing , and cross-section.

Kepplerites sp. A Plate 30, fi gu res 11- 15 ~aterla l and occurrence. One fragmen tary specimen (f igu red specimen GSC 68424) collect ed loose below the sec t ion (GSC loc. 92 473). The litholog y suggests its prob able or igin in Bed 62 (bamstoni Zone).

Dis cussion. The material is not sufficie nt to des cribe in detail. The inner whorl o f the sma ll e r fragment found in pla ce (PI. 30, figs. 17- 19) is run cinate with inci pien t ven t rol a t e ral t ubercl e s. The la rger, still septate gro wt h sta ge o f the same specimen is sim ila r to K. sp, a ft . K. ros enknlnt zi, but ha s a m ere ro unded, apparently lower c rosssecti on. The secondaries trifurcate finely at the still-s t rong la teral nodes, and there are a few add itional in t e rcalated secondarie s. The larger, loose f ragment (PI. 30, fi g s. 20 , 2 1) shows an in termediat e growth stage and par t of t he la rge body chamber. Bot h are subcircula r in cross-sect ion, t he flanks merging smoothly with venter and umbilical wal l, sepa ra t ing it from t he other species o f KepplerUes de sc ri bed he re. The fine ri bbing distingui she s it fr om K. sp, A. The body chamber becomes slightly c on t ract ed and t he r ibs sweep Iceward st rongly near the preserved ape-r ural end, indica t ing pro xim ity to the aperture.

Keppl e r ites (?) sp, C Plate 31, figu res 8-10 .Wa te r ia l and occurrence. One mode rately well preser ved specimen (figu red specimen GSC 68430) fo und loose be lo w the sect ion (GSC loe. C -9H 72), in a matrix that ind ic a tes its de riv ation fro m the tsh mal! or ba ms toni, or poss ibl y e ven the ( rami 01" t.Jrlandi Zones.

Description. The smalle st whor ls tha t can be seen dea r ly Altho ugh t lleY ha ve been tecr cotcan y a re 2 an high. dis toe ted, t he y appear t o be flat- sided, significan tly higher t han wide , and with a venter t!\a t is smoothly rounded and not acumina t e. The umb ilicus is re lativ e ly wide, about I c m , wit h steep walls and an a bruptly rou nded edge. The pr imar y r ibs are closely spaced , and subdivided into man y ver y fine secondaries near the umb ilical ed ge, along a locu s o f sm al l and weak, pointed tubeecjes, The secondaries, a bout t hree to e a ch pr ima ry , sweep f or wa r d fro m t he points o f furcation , and t hen become nea r ly rad ial over the ventr a l ha lf o f t he fl ank.

At a whorl height of about 2.'J c m, pr imaries ar e ve ry short - almost absent - so that line, closely spa ced secondaries competse near ly the en tire ornamentation. Their orien ta tion and cu r va t ure have been distorted tect cmcafly, The c ross-sect ion is fla t-sided , higher than wide , wit h an evenly ro unded ven t er . The last sept um occurs a t a whorl heigh t of 4.4 c m. The c ross-section is as described a bove. The umbili c us is about 1.5 cm wide, ver ticall y wa lled, wi th a roun ded edge. and perhaps show s a slight tendency to ex t ra-u mbilication . \\'ell de fi ned , fi ne ribs persist to t he last preserved part. about one quar ter of a whorl be yond the last septum. Fine ly spaced pr imary ribs occupy the lower si xth of t he flank, ta pering on to t he umbilical wa ll and c urving adorally as they pass over the umbilical edge . The y su bdiv ide there int o muc h more numerous seconda ri es. The suture patt ern is sho wn in Figure 21.

rounded. The cross- secti on is som ewhat compressed. The vent er is smoothly ro unded . The shell a ppears to be strongly involute. No sutwes co uld be t raced. Discussion. The species resembles Keppler l t es(?) sp C in t he general sha pe of t he she ll, th e small um bilicus. and t he sha pe and characte r of t he r ibs. It is not suff iciently well prese r ved t o c o mpar e pre ci se ly. however. It s involute c oiling and fi ne, tiYead-like ribbing, in some wa ys similar t o t hat of Phylloceras, renders its generic as signment que stionable.

Famil y SPHAEROCE RATIDAE Buckman, 1920 SUbfamil y EURYCEP HALlTINAE Thierry, 1976 The SUbfamily was transferred to lamily Spl'laeroceratida e , a nd its derivation and that of subfamily Macrocephalit inae from Sphaeroceratinae was shown by Cal lom on (in Donovan e t a l•• 1980). This is a ci rc um- Pa ci f ic group t hat also re a c hed nort hern Yukon , where it is re present e d by several spec imens of Inis kinites a nd L oucheu.xia, described be low.

Fi gure 21. Septa l sut ure pattern of Keppleri tes(7) sp. C, showi ng last and penultimate septa e; f igured speci men GS C 68430, f r om GSC locality C-9 S372; whorl heigh t 4.3 cm.

Di.!CUS$i on. The c ros s- sect ion and re lativel y small umbilicus differentiate t his specimen fro m other Keppleri tes species described here. Keppleri tes(?) SI'. D is similar and ma y re prese nt the same species (see be low).

Keppl erHes(?) sp D

P la te 23, fi gures 9. 10i Plate 32, f igure I Material and occurrence. One poor l y preserved specimen (f igured specimen GSC 68366) from loca li t y 92540 . f rom Bed 60. Ishmae Zone .

a dult GSC

Speci es peevicusfy referred to MacrocephaHtes in Ame rica , and Arc tic Nor t h wes t er n South and Nor th America and Eur asia . a re now assigned ins te ad t o other gen era (family Cardiocerat idae fo r t he nor thern group , co mprisi ng t\rc t ocepha Utes, t\ rctlcoce ras. and Cadoceras j a nd Eurycephali tes for t he eastern Pa cific group (Hillebrandt , 1976, 1978; Westermann, 1980)]. 1970; Thierry, Macrocephalites is no longer thought to be repr esented in the Ame ricas. Se ve ral western Nort h Ameri can gen era Buckmani cera s Cric kma y, a nd Lil loet tia C rickmay , Wa r rena ceras Fre bold - are as signe d t o Eurycephalf tes a lso , some by We ste r ma nn (I 980l. o thers by t he present writer. The ch arac te ristic e van escent ri bbing beginning around the umb ilicus and spreading gradually ventrally is a lso seen on somewhat older Morri.siceras and M egasphae r"OC'eras. Callomon in Dooo van (I 981) sugg ested that the form er is onl y homeomorpnically similar and t hat t he latter is the earliest member of t he sub family . This character is lacking in the t wo ge ner a (Inlskinites and Loucheu.xia), descri bed her e, mak ing them more sim ila r to both a ncest ra l Sphae roc e rati nae a nd younge r Mac roce phalitinae, t o whic h t hey co uld equall y . we n , be _assi gne d on _t he _basi s - of -their - morpholog y. - The sub fam ily distinc t ions are ar bitrar y (Callomon in Dono va n et al., 198 0 , and are partly based on stratigra phic and paleobiogeographic considera tions .

Gen us Iniskini tes Imla y, 1975

Descn ptl on. The sma ll growt h stages of t he specimen ar e lniskinites was named (Imla y, t9 7}) to inc lude many sou t hern Alaskan a mmoni t~ rnai nlv infla ted_ anL fi ne ly _ poorly preserved. At an int er medi a te growth stage (whorl ---height- about-40 mm).- t1'le-i'ibnlf~-crearl Y-di{fefEilltlated lnt-o--ribbea; t flaf -hid preViOUSly Umla y. 195b I be en de scribed as primary ribs on t he lower hall of t he fl an k, passing into ver y Kh era i cera s Spa t h. Thus. t be t 'JI: : := genus is no longer line secondaries on the upper half (PI. 23. fig . 10). The reco gnize d in Nor th Americ a. l nu l.,.-:ni te s has now been primaries are st rong on t he test s urf a ce , but a lmos t re ported fr om sou ther n Alas1d satisfactOrily; th e shaded po r tion l.s t houg ht to ref le ct the a ctml s ut ure patte rn re asona bl y wel l.

Pla te 29, figures 7- 19; Plate 31, f igur es 1-7

e t t. Scaphltes venm cosus McConne ll, 1891, p, 1230. Ammoni t es sp, inde t , Fre bold , 1961, p, 6, PI. 11, fi g. 3. Mate ri al and occurrence. Sma ll and poorly preserved (unf igur ed) speci me ns of lnis ldni tes ccce- in Bed 62 (GSC loc . 92543) , and t he genus ma y be re presen ted by undeterm inable f ra gments as low in tbe se ctio n as Bed 22 (GSC loc.92,52.5). Several juven ile s pecime ns occu r loose be low the section, in ye llo w- we a t he ring co ncre t ions t hat c le a rly co me from Bed 62 (incl uding figured spe ci me ns GSC 6841 0 from GSC loc.92.5.5I, GSC 684 11 f ro m GSC loc. 92 .561; GSC 68412 and 68416 fr om GSC toe, C-95369; GSC 68413 and 684 14 found together fr om GSC loc. 92413; GSC 68415 from GSC lee . C-95370); one fragment of a large specime n fOlSld loose can be traced by i ts litholog y t o Bed 62 (figured specimen GSC 68427 from GSC toe. 92413); and t wo ot he r figured specimens (GSC 68428 f ro m GSC lee, 92,554 and GSC 68429 from GSC toe. C-953721 by t he ir li thology and as sociated f aun as, to Bed 60. The s tr a tigra phic positi on of t he specimen (fig ure d spe cimen GSC 15137 from GSC tee. 37917) mentioned by Mc Connell (1891) and described by Fre bold (196 1) is not known.

One globose specime n, with a ma ximum preser ved c.e me t ee of 4 on, is en tirely se pt a te (PI. 29, f igs . 16, 17). Tne ribs are f ine , subdi viding along the locus of t he maximum • idt h of t he she ll, abou t one third of the height of t he whorl. ~e shell ap pe ars to begin to flare ra pidly, and the pr imar y r.os become stronger and mor e co ar sel y spa ced in t he oralmost part of t he s peci me n. The suture line is shown in F.gure 22. Another speci me n is cl ose ly sim ila r in t he st yle .1..,d st reng t h of ribbing and th e coili ng an d cross-se ction ( ? l. 29, fi gs. 9, 10). It s su t ure line is shown in Figure 23. One f ragment (PI. 29, f igs. 11, 12) is beoeoer at t he w.-ne whod hei ght, and mai ntains fi ne , prim ar y ribb ing to a k ;:e r growth s tage . The f ine ribbing and becad cross-section also seen in another, si milar fr a gm ent (PI. 29 , figs. 7, 8).

.e

A smal le r spe cimen (PI. 29, figs . 13, 14) is similar in e -css-secncn, whorl sha pe , and general orientation of the r~ . The ribbing is equally fin e to a whorl height of a bout • ~:TI, but then bec omes sign if ic antl y coa rser than in t he

Figure 23. Septa l suture pattern of Infsktni t es s p.; figure d spe c imen GS C 68411, from GSC loc ali t y 9256 1; whorl he ight 2 c m. preViously described specimens. Each of the coarse, pr imar y ribs bif urcate along a locus about halfway u p t he fl ank and t here ar e a few intercalated secondaries. Altho ugh t he a pertur e is som e wha t crushed , t her e appears to be some mod jf ica t ion of the las t 3 or 4 mm , suggestin g t hat t he s pecim en Is " a microcon c h di mor ph. This portion is co ntra cte d, the re is no termi nal flar e but rat he r a smooth hood , weakly projected at the ventrolateral posi t ions• Ribbing he re is weakened slightly and a bit mo re finely s paced t han on im medi a te ly earlier parts of t he shell. One other smaller" spe cimen (PI. 29, fig . I:J) f rom the same bloc k of rock becomes mor e co ar sely ribbe d at about t he same grow t h s ta ge . Two sm all f ra gments exhibit ve ry f ine ri bbing on an in te rior whorl (not f igur ed), and sign if ican tly coarser ribbing on t he outer, nonseptate whorl (PI. 29, figs. 18, 19). This difference in t he strengt h of ribbing differentiates t he specimen from t hose described a bove . There is a s light

61

forward slope to the ribs, accompanied by a slight adapical deviation along the venter. The cross-section is low, and smoothly rounded. A fragment of a large ammonite, probably from the barnstoni Zone (PI. 31, figs. 1-3), comprises part of the body

whorl, and the external mould of part of the preceding whorl is preserved. This earlier whorl has a ventral portion that is broadly rounded. It is finely and regularly ribbed. The ribs are nearly straight but pass over the venter with a very slight deviation in the adapical direction. The body whorl is coarsely ribbed. The ribs are inclined slightly orally and pass straight over the venter. Some are slightly weakened along a line along the venter. Some ribs bifurcate. The specimen may include an apertural constriction and slight weakening of the ribs near it, although this cannot be seen clearly. The two small fragments of large specimens that probably come from the ishmae Zone are preserved in a dense, ferruginous matrix. One (PI. 31, figs. lJ., 5) comprises the apertural part of a large body chamber with the apertural constriction preserved on the umbilical part of the flank. The cross-section is evenly rounded, with flattened flanks, and appears to be widest near the umbilicus. The height is at least 6.5 cm, the width about 6 to 6.5 cm. Strong, subradial, regularly bifurcating ribs are present. They are slightly strengthened and projected over the venter. The other, nonseptate fragment is strongly ribbed. The ribs are nearly radial, slightly sinuous, and bifurcate regularly about halfway up the flank. They pass over the venter without deflection. The cross-section is subquadrate, with flattened flanks and venter. The greatest width is low on the flanks, which slope toward each other vent rally. This specimen has similarities to both Kepplerites and Iniskinites, but is not identical with any described species of either genus. Frebold (1961) described another small, specifically undeterminable specimen. Like the specimen shown in Plate 29, figures 13 and IlJ. of this report, it exhibits weak ventrolaterallappets. R.W. Imlay (unpubl.) has examined the specimens described here and has compared them with several named species, that is I. cf. magniformis (Imlay), cf. varicostatus (Imlay) and cf. martini (Irnlay).

The character of the ribbing and general shell shape of Loucheuxia are close to those of western North American species assigned now to Eurycephalites (Spath, 1928) (i.e, Lilloettia Crickmay, 1930). However, the loss of ribs early in

the ontogeny, beginning first around the umbilicus and gradually spreading vent rally, together with the convergent flanks in mature specimens of compressed species, distinguish Eurycephalites. The shell of Loucheuxia remains strongly ribbed, at least onto the early part of the adult body chamber, and the venter is broader, with subparallel, convex flanks. Only the early part of the body chamber is known, and the mouth border is totally unknown. Additionally, the primary ribs of Loucheuxia are not as strongly outnumbered by secondaries as they are in Eurycephalites. The variation in the degree of compression and coarseness of ribs described in Canadian Eurycephalites (I,e, Lilloettia; see Frebold in Frebold and Tipper, 1967) is also seen in L oucheuxia. The same differences separate Loucheuxia from South American species of Eurycephalites. Some of the specimens assigned to Loucheuxia resemble species of Macrocephalites in their cross-sections and coiling characteristics. Unlike any Macrocephalites species, however, the ribbing of Loucheuxia becomes extremely coarse in the largest growth stage. The characteristic falcoid ribbing found in Loucheuxia is less well developed in Macrocephalites.

The North Pacific genus Umaltites Sei and Kalacheva (1979) was erected for specimens previously assigned to Cranocephalites or Arctocephalites, which are small when adult and have a smooth body chamber that is shorter than that of Arctocephalites. Sei and Kalacheva (1979) thought it to be transitional between Arctocephalitinae and Macrocephalitidae. The ribbed portion of the shell is very similar to the small growth stages of Loucheuxia, but the much smaller size and probably significantly older age of Umaltites differentiate the two. Name. For the Loucheux Group of Athapaskan Indians who inhabit the northern Yukon and upper Mackenzie Delta area.

Loucheuxia bartletti n, sp.

Plate 32, figures 6-9; Plate 33, figures 1-10; Plate 3lJ., figures 1-6, 10-19 Genus Loucheuxia n. gen. Loucheuxia is erected to accommodate more than 12 specimens assigned to the type species L. bartletti n, sp., or to L.(?) spp. lndet, Although the genus is known certainly only at the Salmon Cache Canyon section, some species from the Western Cordillera of Canada and Oregon, currently assigned to Iniskinites, may represent Loucheuxia instead. They have more compressed cross-sections than other Iniskinites species and a different, sinuous curvature of the ribs. These species include Iniskinites acuticostatus Imlay (1981), I. tenasensis Frebold (1981) and perhaps I. robustus Frebold (1978). In addition to the differences listed above, Loucheuxia has a more open umbilicus than Iniskinites and a greater tendency to flat flanks. Additionally, based on the criteria noted above, Arctocephalites(?) multicostatus Frebold, from the Canadian Western Cordillera, may belong to Loucheuxia.

62

All the specimens were found loose below the section in concretions that also contain other ammonites, or that by their dense, ferruginous lithology, indicate their source as the ishmae Zone (e.g, paratype GSC 68370 from GSC loco 9255lJ.; paratypes GSC 68371, 68375, and 68380 from GSC loco 92552; paratype GSC 6837lJ. from GSC loco C-9537lJ.; holotype GSC 68369 and paratype 68372 from GSC loco C-95372), the barnstoni Zone (paratype GSC 68373 from GSC loco 92lJ.73x) or either the ishmae or the barnstoni Zone (paratypes GSC 68377 and 68381 from GSC loc. C-95375).

Material and occurrence.

The specimens available indicate considerable morphological variation, principally in the coarsening of ribbing and the degree of inflation. Natural subdivisions are not readily apparent however, unless the most coarsely ribbed specimen (PI. 33, figs. I-lJ.) is considered to be different from the others because of that single character.

Description.

The holoty pe (PI. 32, fi gs. 6, 7) is t he largest of several, apparen tly identi c al speci mens, with a ma ximum diameter of about I I c m, who rl he igh t 01 6 cm , and width of about ,. , cm. It is entirel y or ne a rly ent ir ely se pt a te . The imer whor ls c a nnot be seen. The she ll is moderately infl a t e d, with ge nt ly r OlJ1de d fla nks, merging sm oo th ly with t he rounded venter an d um bilical e dge. TIle umb ilicus is sm all, de ep, and s teepwalled. The ma ximum widt h is a bout on e t hir d t o tw o fifths the hei gh t of t he whorl. The en ti re shell bears fi nel y spaced, s trongly developed, gent ly fal c oid ri bs. Thei r apparent a doral weakeni ng may be due t o poor prese rva t ion . TIle r ibs ar e ne arly radial ne ar t he umb ili cus, cu r ve f orward on t he tower par t of the fl ank, an d are again ra dial on the uppe r par t o f the fl ank , pas 50ing straight an d e qual ly st rongly a cross t he ven ter . The r ibs bifu rca t e regularly a bo ut ha lf wa y up t he flan k.

The a bo ve desc r ipt ion applies perfectly well t o several other s tout specimens Ie.g, PI. 33, f igs . ' , 6. 9, 10; PI. n , fi gs. 18, 19) on which t ne r ibs c an be seen t o taper do'ol." as t iny t hreads on to t he umbilical wa ll.

A small (unfigur elogies indicat e the probable sour ce as Bed 62 (barns toni Zone): fi glSed specimens GSC 683 6& and 6&376, from GSC localiti es C -9H& 1 and 92" 3 re spect ively, and GSC 68 378 and 6&379 t og e ther fro m GSC locality C - 95 3&3.

Des c';pt lon. One f ra gment (PI. 32, f igs. 4,.5) has a maximum whorl heig ht of 4.7 cm and a .....idt h of 4.2 cm. The cress-section tends t o be slig ht ly a cu minat e, wi t h flanks convergin g ventrall y fr om a ma ximum width at a bout one t hi rd of t he he igh t o f the flanks. The u mbilicus is sm al l wit h a r Ol.nded edge, and steep, or per-ha ps vert ical , wal ls. The re latively f inely spa ced pr imar y r ibs taper onto t he umbilica l wal l, are ge ntly inc lined f orward, an d subdiv ide , at about o ne thi r d 01 t he he igh t of t he l lan k. There is slight st re ngt he ning a t t he point of su bdivisi on. The secondaries , abou t three or four t o each primar y, a re s t rai ght , ve ry ge nt ly inc lined f orward, and are st rong , ma int ai ning or pe r ha ps slig htl y increasing t he ir s t ren gt h a s t !'\ey pass stra ight ove r t he ven t er.

figure 24. Septal sut ure pattem of L.oucheuxia banfetti n. sp.; parat ype GSC 6837 5, f rom GSC lo ca li t y 9~52; whorl height 4.3 cm.

The shell of ano t her specimen is highl y invo lut e , with a sm all, deep um bili cus, s teep umbili c al walls and a mod erately shar p u mbilical edge . It is s trong ly ribbed, an d septate t o t he maxim..." whorl heig ht pr es erved, 3. 7 cm. These lar ges t preserved whorls ar e modera te ly inflated , with a sm oot h, rounded pro fil e except f or t he rela ti ve ly sharp umbilic a l e dge .

6)

The ribs are nearly straight, inclined strongly forward. They are strong but relatively closely spaced, and bifurcate apparently fairly regularly, just below halfway up the whorl flank. They pass over the venter without projection. The other two specimens (Pl. 34, figs. 11-14) have only slightly falcoid ribs and smoothly rounded cross-sections. Discussion. These specimens have straighter ribs than any other assigned to Loucheuxia, and two of the specimens are more acuminate than most of the others. A very slight suggestion of strengthening of the ribs over the venter of these two specimens may indicate that they represent a late form of Arcticoceras, but the ribs are not projected. TIle ribs on the venter of an inner whorl are particularly strong, as in Arcticoceras, and one of the specimens (Pl, 34, figs. 7-9) cannot be distinguished from those fragments figured by Spath (1932, p, 55) as finely ribbed variants of Arcticoceras ishmae, var. pseudolamberti.

Family STEPHANOCERATIDAE Neumayr, 1875 Subfamily CADOMITINAE Westermann, 1956 Genus Cadomites Munier-Chalmas, 1892 Two specimens from northern Yukon are assigned to this genus although they have somewhat more depressed whorl sections than previously described species. Although those specimens bear some resemblance to Kepplerites and might be considered as early forms of the genus, their early whorls, poorly preserved and not figured here, are different from advanced (typical) Kepplerites. At a whorl height of 9 mm (diameter about 27 mm), the cross-section of one specimen (Pl. 29, figs. 20-23) appears to be broad and depressed, unlike the typical high, runcinate, juvenile whorls of Kepplerites. The low, rounded cross-section and coiling of the adult are also closer to Cadomites. Thus, the specimens described here are the first known Cadomites from the Boreal Realm. Cadomites is widespread outside boreal regions and ranges throughout the Late Bajocian and Bathonian and possibly Lower Callovian (Arkell et al., 1957). In North America, it has been previously described from southern Alaska (Imlay, 1980, 1982).

1 cm, diameter about 1.5 cm) are depressed, with umbilical slopes at a 45° inclination, and a broad, gently convex venter. Closely spaced tubercles occur on the abrupt ventrolateral edge, from which primary ribs extend toward the umbilicus and much more numerous and finely spaced secondaries cross the venter with slight, adoral curvature. At a whorl height of 1.4 cm (width 2.4 cm; diameter 3.5 cm), the shell is essentially similar. There are three to five secondaries to each primary. The ventrolateral edge and slope are rounded at this growth stage. The shell remains similar until the largest growth stage preserved. The best specimen has a whorl height of 2.3 cm, a width of 3.6 cm, and a diameter of about 7.2 cm. The ventrolateral edge, venter, and umbilical slope are smoothly rounded, merging together. The ventrolateral tubercles are elongated, merging more indistinctly with the primaries, and there is a slight tendency for a second row of tubercles to develop on the primaries lower on the umbilical slope. The secondaries are weaker, more numerous, numbering five per primary approximately, and are more strongly curved forward. More or less the entire last whorl preserved is nonseptate. TIle aperture is not preserved. The second specimen (Pl. 29, fig. 24) comprises only part of a whorl, with a height of about 2.8 cm, and an inside diameter of 3.5 cm. The cross-section is evenly rounded. The primary ribs are widely spaced and have a node at the locus of subdivision around the maximum whorl width, about halfway up the whorl.

Discussion. The specimens described from southern Alaska by ImJay (1980) have more closely spaced ribs except for one fragment (ibid., PI. 4, figs. 6, 7), which has a more abrupt ventrolateral edge. Another of the specimens described by ImJay (1982) is closely similar, but the whorl cross-section of the northern Yukon specimen is more depressed. The Alaskan specimens are older, occurring with Cranocephalites costidensus. The northern Yukon material differs from most other species described (e.g, Stephanov, 1963; Hahn, 1971; Kopik, 1974) in the straight and more nearly radial rather than prorsiradiate primary ribs, the distinctly forward-curved secondaries, and particularly, the more depressed whorl cross-section. These characteristics, together with the coarse spacing of the primary ribs, and the very fine spacing of the secondaries, are traits very much like those displayed Kopik (1974). C. rectelobatus by C. cros:Jispinosus (von Hauer) illustrated by Hahn (1971, Pl, 9, fig. 9) has the low cross-section, but finer, less straight primaries.

Genus Parareineckeia Irnlay, 1962

Cadomites sp. Plate 29, figures 20-24

Characteristic features of the genus were given by lmJay (1962).

Material and occurrence. One specimen (figured specimen GSC 68417) from GSC locality C-95365 (base of Bed 53; Fauna 6) and another (figured specimen GSC 68418) from a loose boulder that may come from nearly the same leVel, or as high as the Cadoceras bamstoni beds (GSC loe. C-95369).

Only one fragmentary specimen represents the genus in northern Yukon. It probably occurs in the Arcticoceras ishmae beds. The genus has been found in beds spanning the entire Bathonian in southern Alaska according to Imlay (1953b, 1962, 1975, 1980). There, the youngest species of the genus, P. sheUkofana, occurs in the lower part Uniskinites intennedius Subzone) of the lowest zone that contains Cadoceras, the Cadoceras catostoma Zone. The oldest species occur with "Cranocephalites" costidensus.

Description. TIle inner whorls of the best specimen (PI. 29, figs. 20-23), at a whorl height of about 0.6 an (width about

64

Parareineckeia has also been described from central British Columbia (Frebold and Tipper, 1973), Oregon (lrnlay, 1980, 1981) and is considered to be characteristic of the Pacific Realm (Irnlay, 1975, 1980).

Superfamily HAPLOCERATACEAE Zittel, 1884 Family OPPELIIDAE Bonarelli, 1894 Subfamily OPPELIINAE Bonarelli, 1894

Westermann (1980) has placed Parareineckeia Imlay in family Stephanoceratidae (subfamily Cadomitinae Westermann, 1956). The genus originally had been described as an endemic western North America perisphinctid genus lmlay (1962) and by Bourguin (1968) in a review of the family Reineckeidae. The question of its affinities is not resolved in this report.

Parareineckeia sp.

Plate 36, figures 7, 8 A single, fragmentary specimen (figured specimen GSC 68438) was found loose below the section (GSC loco 92520), not associated with other ammonites but in a very dense, ferruginous matrix like that containing Arcticoceras ishmae in the section (ishmae Zone). Material and occurrence.

The four northern Yukon distinct, hollow keel and a broader toward the aperture, birkelundi n, sp, and two Ozycerites sp,

specimens include two with a cross-section that becomes described here as O;rycerites without, described here as

The well developed keel of most Boreal forms described as Ozycerites (see Birkelund et al., 1971), including O. birkelundi described below, distinguishes them from most southern members of that genus. Ozycerites (Liroxyites) keUumi Imlay (1961, 1982) from the Upper Bajocian of Alaska, also possesses this low keel, so that the name Liro:ryites Imlay is available for such Boreal and northeastern Pacific forms, although its original diagnosis (Irnlay, 1961) did not involve the keel.

Genus Ozycerites Rollier, 1909 The shell is entirely evolute, each whorl having slightly concave flanks that slope steeply toward the umbilicus, an abrupt ventrolateral edge, and a gently convex, broad venter that is nearly twice as wide as the flank is high. The largest whorl flank seen has a height of 1.5 cm, the distance from the seam of overlap with the preceding whorl to the ventrolateral margin is 1.3 cm, and the width of the venter is approximately 2.5 cm. The flanks have finely spaced, strong, simple ribs. Each third one, approximately, is enlarged at the ventrolateral edge to form a strong node. The venter is ornamented with finer ribs, which are twice as numerous as the primaries. The suture pattern cannot be seen. Description.

Since Ozycerites was erected, it has been treated by different authors as either a genus or as a subgenus of Oppelia. The writer follows Buckman (1924), Ershova and Meledina (1968) and Birkelund et al. (1971) in differentiating it from Oppelia generically, on the basis of its greater number of auxiliary lobes, its more disc-like shape with an acuminate venter, the lack of secondary ribs on the ventrolateral part of the shell, and the sharper umbilical angle.

Ozycerites birkelundi n. sp, The specimen seems to differ little from the holotype of P. nelchinensis Imlay, which is probably much older, occurring with "Cranocephalites" costidensus in southern Alaska and in central British Columbia (Imlay, 1980; Frebold and Tipper, 1973). The ribs of the present specimen are coarser, straighter, and more nearly rectiradiate than those of P. shelikofana (lmlay), P. hickersonensis Imlay has coarser ribs, which are also prorsiradiate to a greater degree. Discussion.

Plate 35, figures 3, 4, 9, 10; Plate 36, figures 5, 6 ?Oppelia (Ozycerites) sp, Imlay, 1953b, p.75, PI. 26, figs. 1, 2?Ozycerites d. and aff. aspidoides Oppel, Ershova and Meledina, 1968, p, 47 -49, PI. X, figs. 1-6. Ozycerites aff. jugatus Ershova and Meledina. Birkelund, Hakansson and Surlyk, 1971, p.246-249, PI. 1, figs. la-b, 2; PI. 2, figs. 1-4.

Genus et species indet, B Plate 38, figures 11, 12 Part of a medium sized nonseptate whorl (figured specimen GSC 68461) was found loose in a matrix, suggesting its derivation from in or about the ishmae Zone (GSC loe. C-95372). The primary ribs are short, and practically radial, or gently curved forward. Weak, closely spaced secondaries are present on the adapical part of the fragment, and are at least five times as numerous as the primaries. They are also nearly radial or gently inclined forward. The ribbing character allies the fragment with the specimens of Kepplerites sp, B, Cadomites, and Paracadoceras described here, but the badly crushed and distorted specimen appears to be more involute than any of these, and to have a smoothly rounded umbilical edge and a stout, rounded cross-section.

and occurrence. Two specimens (holotype GSC 68434 and paratype GSC 68437) found loose below the section (GSC loes. 92554, and C-95354, respectively), both in boulders together with Arcticoceras ishmae or Arcticoceras sp. and in a matrix indicating their source in or near Bed 60. lshmae Zone. Material

Description. The largest specimen (PI. 35, figs. 3, 4, 9, 10) is septate to its maximum diameter, 15.8 cm. The early part of the shell (PL 35, fig. 9) has closely spaced falcoid ribs on the ventral half of the flank. The umbilical half cannot be seen clearly, but the ribs appear to die out toward the umbilicus and there appears to be no spiral groove. Beyond a diameter of about 4.5 cm, the shell is apparently smooth although

65

vague swellings cont inuing to t he e nd of t he she ll may represent weak , coarsely spa ced ribs. The whe el section , even a t an ear ly growth stage with a diam e ter of 3•.5 c m (PI. 3.5, fig. 10) ex hibits flanks t hat ar e subparalle l on their um bilical halves, beco ming ro cn de d vent s-ally and wi t h Tbe ne arly sligh tly de veloped ve nt rola t e ral should e rs. parallel flanks and ventrolater al shoulders a re e xaggerat ed in the adult. The external shell sc ulpt ure is preser ved only in a small area near the umbili cu s on t be oute r whorl, where it comprises fine growth lines. No Iirae appear to be prese nt o n the juve nile she ll. The umbilica l wa ll is high and stee p, sligh tly re ve rsed, meeting t he flank at a sharp angle . A dis tinc t keel is present on all growt h stages seen. The su tu re line , t ypica l of t he fa mily, is sho wn in Figu re 26.

Another Siberi an species , O. Wlda tus Ers hova and we tedma (1968) is smaller, more wea kly ribbed , and is keeled o nly on juve nile growt h stages. OJ:)'Cerites cl. and aft. D:rycerite s aspidoides , also described by Ers l-.:lva and \teledina (1968) , from Siberia do not differ significantly from D. birkelundl but ca nnot be co mpared meaningfully beceuse of poce preservation. The sculpt ure . shape, and presence of the kee l link t he spe cies with a specimen described as Dppelia (D.ryceri tes J from the Bureya Basin of far eastern USSR by Set a nd Ka lacheva Cl 919). although those authors (p. 28) did not correlate them with the other Siberian or Alaskan form s. Ce r tai n North Ame rican species, such as Dppelia (Liroxyi tes) k'el lum i (Imla y, (1961, 1962b, 1982) and Dppelia (Dryc e ri tes) chi nitnana Imla y (J 9.53b) o f southern Alaska also ha ve a distinct ven t ral kee l. D. Icellumi is smaller , more stron gly ribbed and has a weakl y cr en ula ted keel. The whorl section of O. chinitnana Imla y (I 9.53b, p. 14, PI. 26, figs . 3-6) is similar, but t ha t spe cies is much smal le r when adult. The specimen f igur ed as D. (D.) sp. by Imla y (I 9H b, p. 1.5, PI. 26, f igs. 1, 2) resembles t he Por cupine River specimen in its feeble sculpt ure and slight inflation. One specimen fro m western Canada de scribed as D:ryce rUe.s (Fre bold, 19.51. p. .54, PI. 28, f ig. 2) has a keel, but , bes ides lacking t he slight ventrolat eral shou lde rs, has stronger ribbing than O. btrkel undi. Other specimens fr om Can ada (Fre bold, 19.51, p• .54, PI. 28, fig . la , b; Prebold and Tipper, 1913, PI. I, f ig. 6) lac k th e keel•

Ff~

26. Sep tal suture pattern of O:ryceri tes bi rfcellld It. f room GSC sp.: fi gured ' pe cimen GSC 68 434, loca lity 92554; wnon heigh t 8.5 cm .

For T. Birke lund, for her contributions to w esczc tc paleontology and biostratigraphy.

.Ne-ne,

O:rycerites sp, The ot her specimen (PI. 36, figs• .5, 6) is septa te t o its The flanks are largest preserved diame ter - 11. 1 cm .

Plate 3.5. fig s. 1, ! ; Plate 36. f igs. 1_4

smoothly convex except ne ar the umb ilicus , ....-reee t hey are flat . Weak, widely spaced. broa d. subr adial t o slightly rurs iradiat e ribs occur on the med ian part of t he ir out er halves . Much more closely spaced, strongl y r ursiradiate ribs or nam en t t he ven t ra l half of the flank a t a sm all er growth stag e (whorl height 3 cm). The change from finely spa ced to more coar sely spaced ribs seems to be abrupt, at a whorl height of about 3.1 cm. A distinct keel is presen t, t he um bilical edge is shar p.

Material and ceewrence, Two spe ci me ns (figured speci me ns GSC 6M3.5, 684361 found loose belcw t he section (GSC toes . C- 9.53S2, C-9H14 re spe ctive ly), both i n bou lde rs togeth e r with other a mmonites , and in a roc k ty pe which indica tes their probable source in o r near Bed 60. Ishmae Zone.

Description. One specimen was large , but only t he juve nile whorls at e well preser ved (PI. 3.5, figs. 1, 8). The specimen Disc ussion. Tbe present species is apparen t ly iden t ical to O:ryceri tes aff. /uga tus , fr om t he .... eenceee-cs bed s of East was septate to at least a lull whorl le ngt h beyond t he siz e The f igur ed , that is, beyond a dia meter of 1 cm . No ribs can be Greenland, described by Birkelund et al. (191 0 . comparison extends t o the varia tion in strength of the dearly seen at any gro""..t h stage. nor is there a ver y distinct vent rol a t eral ribs, and to t he spiral oc-nament on the eMly keel 0( vem rctateeei shoulder. At a diameter of 1 c m, th er e and late growth stages. The species diff ers fr om D. Jugatus is a ver y faint sugges ti on of a spira l ridge about two f ift hs of (Ersl-.:lva and Meledina, 1%8; Meledina. 1( 13) reportedly the way up t he fl ank. Fr om t his locus, t he lIanks converge associated with Arctoce phalite.s in Sibe ria , in ha ving toward t he venter . At smaller growth stages t he re is a som ewhat wea ker ribbing on the inner wbcets. growing to a someo.vhat grea ter tendency for t he flan ks to be subparallel , sloping steeply tow ard t he vent er only on t heir outer part. large r size , and in being ribbed , to some e xt en t a t le ast , at The sut ure line (Fig. 26) is neill'"ly__--,; Th< ~ suture line 01 t his specimen is shown in Figu re 21. The la te gro wth stages. umbttfca.l @dge 1nhatply rounded. identical- to t hat ofD.- jugat~Ershova-and--\tetedina,- t '96!t Fig. 0 , and of D:rycerite$ aspidoides (Oppel; see Arkell. 19.5» alt hough in the standard l igures of D. w ptdoides Ie .g, M ell The juvenile whorls of anot he r large spe cimen (PI. 36, et al., 1951, Fig. 320. la) the pronounce dly bifid character of figs . 1-4) are conspicuo usly but weakl y or name nt ed by t he second la teral sadd le and the accessoe y sad dles on i n modera tely spaced fal coid ribs o n th e ve nt ra l half 01 t he ve ntral side ar e not as distinct as in the northern Yukon flank. In t his and near ly e ver y ot her ch aracteris tic, this specimen. specimen resembles the one descr ibed above and sho wn in

'The o th e r specime n (P I. 3.5, figs. 1, 2) is septate t o its ma xim um peeser ved size - whorl he ight 1. 1 c m, diameter 2..5 c m. The umbilicus is wide , and expands rapid ly at the lar ges t grc wt h stage p -eservee. The u mbilic al edge is rounded, t be wat ts ver-tical, the flanks are only ver y s ligh t ly conve x. ....ith ma ximu m conch wid t h around t he umbilical edge . The la t eral shell surf ace is not peeseev ee , t hus detailed ornamenta tion c an no t be seen. C oa rse ribs, cur ved Iowerd at the ir ven tral ends, o rnam ent t he ve ntral pa rt o f t he fl a nk, weakening r a pidly dOf sall~' . On t he internal mould, t he ven t e r is shar pl y r ounded. presuma!:lly the bas e of a distinct keel t ha t is not pr-es e r ved . we ak, vent r ally inclined thread- like ex tensions of t he r ibs co nt inue on the nar ro w, near-ly smoo th space be t ween t he ven t e r it self and t he ventrolateral shoulder form ed by the s tr engthen ed ribs. F igure 2 7. Septal suture pattern of Ozycerite8 sp.: figured specimen GSC 68 435, from GS C locality C -95332: 1,;1101"1 height 3. 7 cm.

The sutu re pattern of this specimen is figu red (F ig. 28). It is crw e cterts u c o f the fa mily Oppeliidae.

Ptate 35, figu res 3, 4, 9, and 10. Hcwever , a very "'eai