Birds (Prehistoric Life)

Contents Flying Beasts

4

The Age of Archosaurs

6

A Different Earth

8

Adapting to Change

9

Bird Fossils

10

Revealing Evidence

12

Ornithologists

13

Bird Groups

14

Birds Closeup

16

Life Cycle of Birds

18

Feeding Habits of Birds . . . . 20 Disappearing Act

22

Prehistoric Birds Onscreen . . 24 Digging for Birds

26

Further Research

28

Ancient Activity . . . . . . . . . . 29 Quiz

30

Glossary

31

Index

32

Flying Beasts

B

irds have lived on Earth for a long time. When dinosaurs roamed the world, prehistoric birds also filled the skies. Scientists think the first birds appeared on Earth about 150 million years ago, during the Late Jurassic Period. There were many types of prehistoric birds. They ranged in size from very small to very large. Many died out along with the dinosaurs at the end of the Cretaceous Period, about 6^ million years ago. Even though many birds disappeared, others continued to live and are still living today.

Pterosaurs were flying reptiles, not birds. They had wings, but no feathers. A leather membrane covered their wings. Their wings ranged in size from a few inches to more than 40 feet (12 m). 4

FLYING BEASTS

Albertosaurus\N3S a theropod, which means "beast footed." Most theropod dinosaurs walked on two legs.

Today, many paleontologists believe that birds actually evolved from a type of dinosaur called a theropod. Theropods were meat-eating dinosaurs that shared many features with modern birds.

FACTS ABOUT FLYING ANIMALS The largest known flying animal was Quetzacoatlus, a member of the pterosaur family, it had a wingspan of 40 feet (12 m) or more. Quetzacoatlus \N3sf'\[s\ discovered in Big Bend National Park, Texas, in 1971.

• Some scientists are not sure if the Archaeopteryx, the first known bird, used its feathers to keep its body temperature normal or if it used its feathers for flight.

BIRDS

5

The Age of Archosaurs

F

or more than 3.5 billion years, living things have grown and developed on Earth. Scientists have divided Earths history into blocks of time called eras. The eras are divided into periods. The dinosaurs lived during the Mesozoic Era, often called the "Age of Dinosaurs."

PRECAMBRIAN ERA

PALEOZOIC ERA 545 Million to 250 Million Years Ago

•^ Paleozoic means "ancient life." During this era, more complex life forms appeared on Earth, including fish, insects, land plants, and reptiles. Algae fossils

4.6 Billion to 545 Million Years Ago

During the Precambrian Era, simple life forms first appeared in the seas.

Trilobite fossils 6

THE AGE OF ARCHOSAURS

Some scientists think the Mesozoic Era should be called the "Age of Archosaurs." The archosaurs were a large group of animals that included birds, dinosaurs, and pterosaurs, or flying reptiles. The first known bird was the Archaeopteryx. It is thought to have appeared at the end of the Jurassic Period about 150 million years iigo. The Archaeopteryx shared features with the birds that are alive today and dinosaurs. It had bird-like features, such as feathers, wings, a wishbone, and light, hollow bones. It also had dinosaur-like features, such as a full set of teeth, a long tailbone, and three claws on each wing.

MESOZOIC ERA

CENOZOIC ERA 65Million Years Ago to the Present Cenozoic means "recent life." All types of mammals began to appear on Earth during the Cenozoic Era.

Brontotheres sk\.\\\

250 Million to 65 Million Years Ago • Mesozoic means "middle life." Dinosaursand birds appeared during the Mesozoic Era. By the end of this era, many of these animals became extinct.

Oldest-known hat fossil

BIRDS

7

A Different Earth

D

uring the Mesozoic Era, when birds first appeared, Earth was much warmer than it is today. In the Triassic Period, the land on Earth formed one large continent called Panguea. The climate was warm, the sea level was high, and there was no ice at the North Pole or South Pole. During the Jurassic Period, Pangaea began to divide into separate continents. The climate grew moist, and forests became thicker. In the Cretaceous Period, the land continued to shift and change. The climate was warm, and there were wet and dry seasons. By the end ofthe Cretaceous Period, the continents looked much like they do today.

THE CHANGING CONTINENTS

Triassic Period One continent called Pangaea

8

A DIFFERENT EARTH

Jurassic Period Pangaea begins to break apart

Cretaceous Period Modern continents begin to form

Adapting to Change The Dodo's hooked beak may have been used to catch fish. The Dodo lacked the strong chest muscles needed for flight.

The Doc/o did not need to fly, so it developed small, weak wings.

DODO

A

s Earth changed, animals adapted to fit into their environment. Paleontologists agree that the first bird was the Archaeopteryx, but after that, they disagree about the history of birds. Some scientists think that birds evolved from meat-eating dinosaurs called theropods. Today's birds share many features with ancient theropods, including light, hollow bones. Other scientists believe that birds evolved from early reptiles called thecodonts. Crocodiles, dinosaurs, and pterosaurs all evolved from archosaurs. BIRDS

9

Bird Fossils

P

rehistoric birds lived on Earth a long time ago. It is not possible to go back in time to see them. It is possible to learn about them by looking at their fossils. Fossils are the rocklike remains of ancient animals and plants. Some fossils are bones and shells, and other fossils are impressions of feathers, leaves, and skin. Feather impressions found in ancient rocks have helped scientists identify prehistoric birds such diS Archaeopteryx.

Hardened tree sap, also called amber, can preserve items so well that even the individual fibers of a feather are visible. 10

BIRD FOSSILS

T T M

' I

Sedimentary rock, where many fossils are found, is made of strata, or layers. Exposed sedimentary rock often can be found on cliffs and riverbanks or in desert badlands.

HOW FOSSILS ARE FORMED Paleontologists have found the fossils of many different prehistoric animals. A fossil is created when layers of mud and sand cover the bones of an animal that has died. As time passes, layers of mud build up. The weight of the upper layers of mud pushes down on the lower layers to form solid rock. Bones or plant materials become fossils.

Bird fossils afe not as common as dinosaur fossils. Birds had light, hollow bones that did not always last long enough to become fossils After a bird died, it sometimes rotted away or was eaten by other animals before its bones could get trapped in mud.

BIRDS

11

'

Revealing Evidence

E

very new fossil helps paleontologists understand what life was like on Earth long ago. By looking at fossils, scientists can get a better idea of how large an animal was, when it lived, whether it walked on the ground or flew through the air, and if it lived alone or in a herd. Paleontologists are much like detectives. They try to learn as much as they can from the evidence, or clues, they find. In order to identify a bird fossil, paleontologists look for special features, such as impressions of feathers, a wishbone, or bird-like hips. These are the features that prehistoric birds such zs Archaeopteryx had in common with modern birds. Scientists think that Archaeopteryxy^3s a weak flier. It probably was best at gliding, leaping, and running.

12

REVEALING EVIDENCE

CAREER LINK

Ornithologists

A

n ornithologist studies birds. They may study the behavior of birds, where birds live, and how birds interact with their environment. Ornithologists may also be involved in saving birds that are in danger of becoming extinct. Ornithologists can work for government agencies or other organizations. They may work with wild birds, in a laboratory, or on their computer. Some study a particular bird group, while others are interested in all birds. Ornithologists perform many different types of jobs, and they use a variety of tools. If they work in the field, they may use binoculars, telescopes, and nets or traps. If they work in a laboratory, they may use microscopes, test tubes, cages, and computers. To become an ornithologist, you need to do well in science and math classes. You should also develop the language skills necessary for writing reports.

Ornithologists sometimes catch and tag birds in order to track their migration patterns. BIRDS

13

Bird Groups

B

irds can be divided into two major groups: the advanced fliers and the flightless birds. Scientists believe that the type of dinosaur most closely related to birds is a group of dinosaurs called theropods, a group of bipedal dinosaurs. Theropods share so many features with today's birds that some scientists believe that birds actually are theropod dinosaurs. One very bird-like dinosaur was the Deinonychus. This dinosaur did not have feathers and could not By, but its distinctive hipbone is similar to the hipbone of a modern bird. This has led scientists to believe that modern birds evolved from Deinonychus, or a dinosaur

very much like it.

The hipbone of theropods allowed them to stand and walk upright. Modern birds have the same type of hipbone. 14

BIRD GRDUPS

ADVANCED FLIERS: NEOGNATHOUS BIRDS Most modern birds belong to the neognathous, or advanced fliers, group. Many scientists believe that all birds developed features for flight Birds needed to be very light to get off the ground and stay off the ground, so they developed hollow bones. They also needed to stay in the air once they were in the air. That is why birds developed wings and feathers.

flapped its arms to get into the air Others think that the small theropod gradually developed wings in order to glide from tree to tree. The discovery of the Microraptorgui'm China supports this theory. This small flying dinosaur had four wings—one on each arm and leg.

How Deinonychusïr]\qhX have developed into an animal that could fly is still a mystery to scientists. Some believe that Deinonychus ran quickly and

FLIGHTLESS BIRDS: PALAEOGNATHUS BIRDS There are still a few species of palaeognathus, or flightless, birds alive today. Scientists think that flightless birds lost their ability to fly because they were not threatened by dangerous predators. They had no reason to leave the ground.

Flightless birds still exist in places such as Africa, Australia, New Zealand, and South America.

Ostrich

BIRDS

15

Birds Cioseup

M

any different kinds of birds lived in prehistoric times. Some were the size of a chicken, while others had 25-foot (7.5-m) wingspans. There were birds that stood 12 feet (3.7 m) high and others that weighed 800 pounds (363 kg). There were flightless birds and birds that could fly.

Diatryfna was first discovered in 1874 in New Mexico. Diatryma was a large, flightless, meat-eating bird. It lived 53 million years ago.

16

BIRDS CLDSEUP

ARCHAEOPTERYX • • • • •

Believed to be the first bird Same size and weight as a crow Appeared in the Late Jurassic Period Probably ate insects and small plants Shared many characteristics with both birds and reptiles

I

ANOALGALORNIS Large, meat-eating, flightless bird that lived in South America Peaked in numbers during the Tertiary Period, 65 to 1.8 million years ago Ran fast and had large hooked beak Replaced by other predators such as the jaguar and puma

AEPYORNIS

MOA

•

Extinct flightless bird that lived in New Zealand First appeared 82 rriillion years ago Could reach 12 feet (3.7 m) and weigh more than 660 pounds (299 kg) A plant-eater Extinction caused by early humans in New Zealand

DOOO About the size of a large turkey A flightless member ofthe pigeon family Had short legs, a large beak, and tiny wings Killed by European sailors for food and spoit Became extinct about 1680

• •

•

•

Flightless bird Stood 9 feet (2.7 m) high and weighed more than 8Ü0 pounds (363 kg) Seven species lived on the island of Madagascar; some survived until the seventeenth century Had tiny wings and long, sturdy legs

ARGENTAVIS Had a 25-fnot (7-6 mjwingspan Weighed 265 pounds (120 kg) Lived about 5 to 8 million years ago Ancestor ol some vultures and storks Thought to be a very fierce predator

BIRDS

17

Lile Cycle of Birds

L

ike reptiles and dinosaurs, birds lay eggs. Prehistoric bird eggs came in many shapes and sizes. Some were tiny. Others were very large. The size of the egg would usually depend on the size of its mother. It is rare to find fossilized eggs because they are very fragile. The largest bird egg fossil ever found belonged to iheAepyomis, or elephant bird. This enormous bird produced an equally enormous egg—it weighed 22 pounds (9.9 kg). Sometimes, when paleontologists find a fossilized egg, they discover a tiny, fossilized embryo of a bird inside. This is unusual and very special.

quail egg chicken egg 18

LIFE CYCLE OF BIRDS

ostrich egg

elephant bird egg

The tiny hummingbird lives from 3 to 5 years. The large ostrich can live for 75 years.

Scientists do not really know how long prehistoric birds lived. The length of a prehistoric bird's life was probably different for each species of bird. Some scientists believe that prehistoric birds lived as long as modern-day birds. Paleontologists believe that larger animals lived longer lives than smaller ones. Large birds, like New Zealand's moa, might have hatched out of an egg, grown up, and lived a much longer life than the small dodo, another flightless bird.

EGGS FOR LUNCH? Laying eggs might have led to the extinction of some prehistoric birds, such as the Diatryma. Because the Diatryma laid its eggs on the ground,

other animals could easily find and eat them. Paleontologists think this is why the Diatiyma became extinct.

BIRDS

19

Feeding Habits of Birds

E

ven though birds probably evolved from meat-eating dinosaurs, some became meat-eaters, while others became plant-eaters. Some birds, such as the moa, were large, slow-moving, plant-eating birds. The moa is thought to have eaten fruits, seeds, and vegetables. Other birds, such as the Argentavis, were meat-eating birds. They had powerful legs that allowed them to run very fast. Once they caught their prey, they could easily tear it apart with their sharp talons and hooked beak.

N 20

F E E D I N G H A B I T S OF B I R D S

A new species of puff bird was discovered in Lincoln County, Wyoming. It lived approximately 50 million years ago and likely ate insects, just like modern puff birds, which live in tropical North and South America.

Food Weh SUN

DECAYING BIRD REMAINS

PLANT-EATING BIRDS MEAT EATING BIRDS

FOOD WEB Just like life today, all life in prehistoric times relied on an exchange of energy, also called a food web. For birds, this food web began with plants. The plants made their own food by converting the Sun's rays into energy. These plants were eaten by herbivores,

or plant-eaters. The herbivores were eaten by carnivores, or meat-eaters. When a bird or any other living thing died, its body would break down and provide food for plants.

BIRDS

21

Disappearing Act

A

lmost half of the worlds animal and plant species became extinct at the end ofthe Cretaceous Period. Some scientists think these animals and plants became extinct because the climate became colder. Other scientists believe that a huge meteorite crashed into Earth and hurled tons of dust into the air. The dust formed a thick cloud that blocked out light from the Sun. Soon, plants died because they could not get enough sunlight. Plant-eating animals starved to death. Losing their prey, meat-eating animals died, too.

The dodo evolved into a non-flying bird after settling on the island of Mauritius in the Indian Ocean. The introduction of new animals onto the island and the use of the dodo for food caused it to become extinct by the 1680s.

22

DISAPPEARING ACT

Although bird fossils are not as common as dinosaur fossils, many of them contain details that are helping scientists explain how birds evolved.

Many different species of birds had developed by the end ofthe Cretaceous Period. Some disappeared in the mass extinction, although paleontologists are not sure how many species became extinct. Hesperornithiform birds, which were flightless birds that spent most of their time in water diving for food, disappeared with the dinosaurs, ¡chthyornis, z fiying bird with teeth, also disappeared about the same time. Although primitive birds with teeth disappeared at the end ofthe Cretaceous Period, many toothless birds survived this mass extinction. The birds that survived the great extinction eventually developed into the land birds and water birds of today.

AN OLD THEORY OF EXTINCTION Early scientists once believed that ancient warm-blooded animals, the ancestors of modern-day mammals, were responsible for the disappearance of the dinosaurs.

According to this theory, small, furry animals ate all of the dinosaur eggs. Today, this theory isas extinct as the dinosaurs.

BIRDS

23

Prehistoric Birds Onscreen

I

n modern culture, dinosaurs receive most of the attention given to prehistoric animals. They are everywhere^on television, in movies, in books, and on cereal boxes. Prehistoric fliers do not appear nearly as often in books and movies.

Pterosaurs are popular characters in movies and television shows such as Jurassic Park III, Dinotopia, The Flintstones, and The Lost World 24

PREHISTORIC BIRDS ONSCREEN

Flying animals do appear in movies, but most of these animals are flying reptiles. In 1933, a scary-looking pterosaur was featured in the movie King Kong, This enormous creature tried to pull Fay Wray, the lead character, off a cliff. Many prehistoric birds looked like the birds seen today. Instead of waiting to see a prehistoric bird on a movie screen, just go birdwatching.

Unlike their prehistoric ancestors, modern meat-eating birds do not have teeth and have to tear their food apart with theii beaks.

YABBA DABBA DOO! In the cartoon, The Flintstones, cartoon people live among dinosaurs. In the cartoon, people strapped seats to the backs of pterosaurs and used them as airplanes. The Flintstones also used prehistoric birds as feather dusters. BIROS

25

Digging for Birds I

t is unusual to find fossils of flying animals because their bones are light and easily destroyed. Even so,

paleontologists niake exciting discoveries every year. This map shows some exciting discoveries of prehistoric birds and flying reptiles.

In 1872, Benjamin F. Mudge found the first IchthyornisiossW in Kansas. The fossils of several species of this gull-sized bird have been found all over North America.

In the mid-nineteenth century, fossils of giant flying reptiles were found in chalk deposits in Kansas.

In 1983, a very large Argentavis fossW was found in Argentina. The bird would have weighed 265 pounds (120 kg} and had a 25-foGt (7.6-m) wingspan.

26

D I G G I N G FOR B I R D S

In 1784, the first pterosaur was discovered in a limestone bed in Solnhofen, Germany. Pterosaur remains are still being found tbere.

In 1861, the first Archaeopteryx skeleton was found in limestone beds in Germany. At first, scientists thought the find was a pterosaui, or flying reptile, but they were wrong. Seven fossils and a feather have been found in the same place.

In 2003, Chinese fossil hunters discovered a new species of flying dinosaur and named it Microraptor gui. It was the size of a pigeon and had two sets of wings on its front and back legs. Scientists believe it used its wings to glide from tree to tree. For this reason, scientists believe the Microraptor gui mghx be the link between dinosaurs and birds.

Hundreds of moa fossils were found in a swamp in New Zealand in 1937 ANTARCTICA

Í311 Miles 1501 Kilometers

BIRDS

27

Further Research WEB SITES For information about different kinds of prehistoric life, including birds, visit: http://www.enchantedlearning.com For more information about prehistoric life, visit: http://www.tyrrellmuseum.com To find out how to become a paleontologist, visit: http://www.paleosoc.org To find out the latest buzz in the world of paleontology, visit: http://www.ucmp.berkeley.edu/diapsids/dinobuzz.html

Arnold, Caroline. Dinosaurs with Feathers: The Ancestors of Modern Birds. New York: Clarion Books, 2001. Matthews, Rupert. Pterodactyi. Chicago: Heinemann Library, 2003. O'Donnell, Kerri. Birds: Modern-day Dinosaurs. New York: Rosen, 2002. Shealy, Dennis. Dinosaurs Alive! The Dinosaur-Bird Connection. New York: Random House, 2003.

28

FURTHER RESEARCH

Ancient Activity

I

magine you are a paleontologist. Your job is to compare

Archaeopteryx with

modern birds to see how closely they are related. What features rr\2ike Archaeopteryx a

bird? What features m2.ke Archaeopteryx a

dinosaur? Think of as many things as you can for each, and then check your answers below.

BIRDS 2 9

Quiz Based on what you have read, answer the following questions: 1. What type of dinosaur do paleontologists think was the ancestor of birds? 2. In which era did Archaeopteryx Wyel 3. Which flightless bird stood 9 feet (2.7 m) high? 4. Name the flying dinosaur discovered by Chinese fossil hunters in 2003.

5. How were prehistoric baby birds born? 6. What two theories do paleontologists use to explain how birds started to fly? 7. What is the largest known flying animal? 8. When did many birds become extinct?

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Glossary adapted: adjusted to different conditions or environments bipedal: an animal that walks on two legs continent: a large land mass distinctive: a feature that makes something unique or special embryo: what an animal is called before it is born environment: an area in which something lives evolved: changed slowly overtime extinct: no longer alive anywhere on Earth mammals: warm-blooded animals that give birth tc live young, have hair on their bodies, and produce milk for their young

migration: the movement from on3 region to another for feeding or breeding paleontologists: scientists who study dinosaurs and other prehistoric animals predators: animals that catch and eat other animals for food pray: an animal that is hunted for food species: a group of animals that are similar and can breec together tboory: an idea that explains an event or fact wisbbone: a special bone that is the right and left collarbones fused together; founc only on birds

meteorite: a body of rock from outer space that has reached Earth

BIRDS

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Index Aepyornis Albertosaurus amber Andalgalornis Archaeopteryx 12,17,27,29 archosaurs Argentavis carnivore Cenozoic Era Cretaceous Period 22,23 crocodiles

17,18 5 10 17 5,7, 9,10

Jurassic Period

7 17,20,26

Mesozoic Era meteorite Microraptor gui moa

21 7 4, 8,

mammals

4, 7, 8,17 7, 23 6, 7, 8 22 15, 27 17,19,20,27

neognathous

15

ornithologists

13

18,19,23 18

palaeognathus 15 paleontologists 5,9,11,12 18,19,23,26,29 Paleozoic Era 6 Pangaea 8 period 6 Precambrian Era 6 pterosaur 4, 5, 7, 9, 24, 27 Quezalcoatlus

food web 21 fossil 6,7,10,11,12, 18,23,26,27

theropod Triassic Period

herbivore

wishbone

32 INDEX

23,26

9

Deinonychus 14,15 Diatryma 16,19 dinosaur ....4,5,6,7,9,11,14 15,18,20,23,24,27,29 dodo 9,17,19,22 eggs embryo

Ichthyornis

21

5, 9,25 5,9,14,15 8 7,12,29