Contents
Out of the Past . . . 3
Since the World Began . . . 4
How We Find Out . . . 6
• The Age of Reptiles . . . 10 •
The Ruling Reptiles . . . .. . . . 14
Giant Plant Eaters . . . .. . . 16
Lightweights . . . 22
Giant Meat Eaters . . . 24
Plated Dinosaurs . . . 28
Armored Dinosaurs . . . 30
Duckbills, Boneheads, and Parrot Beaks . . . 32
Horned Dinosaurs . . . 36
Flying Reptiles . . . .. . . 40
Marine Reptiles . . . 42
Early Birds and Mammals . . . 46
A GOLDEN
EXP··LORING EARTH
BOOK
DINOSAURS
Dinosaurs-those "terrible lizards" of thepast-illustrated in full color; mammoth plant eaters, terrifying meat eaters, strange duckbilled and armored giants, flying reptiles, and huge creatures from ancient seas; fascinating facts about these and
many more
�GOLDEN PRESS
. ®By Alice Fitch Martin and Bertha Morris Parker Illustrated by Hamilton Greene, Robert Korta, Rudolph F. Zallinger and others Cover by Rod .Ruth
Western Publishing Company, Inc. Racine, Wisconsin Copyright© 1973 by Western Publishing Company, Inc. Illustrations on pages 22, 36, and 46
from CREATURES OF THE PAST© 1965 by Harper & Row. All rights reserved, including the right of reproduction in whole or in part in any form. Printed in U.S.A. GOLDEN PRESS@, GOLDEN, and A GOLDEN EXPLORING EARTH BOOK are trademarks
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When such a life-size restoration is electronically animated, the creature seems· almost as rea l as the animals we see at the zoo.
Out of the Past
No one has ever seen a dinosaur, andno one ever will. The dinosaurs were long gone from the earth by the time man appeared. Our mammal forerunners of dinosaur days were hairy little creatures that probably spent most of their lives just grubbing for food and trying to keep
out from under the dinosaurs.
The name dinosaur comes from two Greek words meaning "terrible" and "lizard." Actually, the dinosaurs were not lizards, although, like the lizards, they were reptiles; and many of them were not terrible at all. They were given the name because some of the first ones scientists
found out about were huge and power ful meat eaters.
In their time, the dinosaurs were nu merous and widespread, and there were many different kinds. Some were big, some little. There were tall ones, short ones, long ones, and flat ones. Some walked on two legs, some on four. There were dinosaurs with horns, dinosaurs with webbed feet, and dinosaurs with heavy coats of armor. There were toothless dino saurs and dinosaurs with so many teeth that you could count them by the hundred. Hooves, claws, spikes, topknots, and ruff like collars of bone are among the great variety of things that fitted different kinds of dinosaurs for their particular ways of life. One thing, however, all dinosaurs had in common: They had legs that lifted their bodies up off the ground so that they could run or leap or stomp about.
During most of their stay on earth, the dinosaurs were the undisputed rulers of the land. Their reign-the longest in the history of the earth-lasted for more than
100 million years. What ended it is a mystery.
As recently as about a hundred years ago, no one even guessed that there had ever been such animals as dinosaurs. Today their name is a household word. We have toy dinosaurs and books and games and puzzles about dinosaurs. There are dinosaur cartoon characters in the movies and in comic strips. We can go to museums and see mounted skeletons of dinosaurs. Some parks and museums have life-size restorations we can look at and wonder at. The picture shows such a res toration of Stegosaurus, one of the so called plated dinosaurs.
Since the World Began
Even as long ago as the days of dinosaurs, the earth was old. It had been wheeling around and around the sun, spinning as it went, for billions of years before there were dinosaurs. In the be ginning, there were no living things at all.
The chart below tells a little of the story of the earth, from its birth some 5 billion years ago down to the present. Most of it stands for a long stretch of time about which we know very little. The part of earth history we know most about is the part included in the narrow bands at the far right-the bands that cover the 600 million years of the Paleo zoic, Mesozoic, and Cenozoic eras.
The Mesozoic, which lasted 165 million years, is often called the Age of Reptiles. It was through much of this time that the dinosaurs ruled the earth. Our own era,
birth of Earth-4.5 billion years ago
the Cenozoic, began only 65 million years ago. To show, on the same scale, the time man has existed would call for a division at the right too fine to see without a mag nifying glass.
Scientists cannot say just how the earth began. One idea that seems to be borne out by Apollo moon findings is that the earth was formed by the banging and sticking together of bodies like our moon as they whirled around .the sun. Even tually, heat built up deep inside the young earth, and the rocky core turned molten. Volcanoes spewed out lava.
The early atmosphere was a mixture of ammonia and other poisonous gases. In it floated a dense canopy of clouds, formed from water vapor escaping from the rocks. Rains poured down and grad ually formed the ocean. There life began. oldest known rocks-formed 3.5 billion years ago early living things chlorophyll appeared in plant cells 2.5 billion yea rs ago
The time when that first living thing ca pable of producing others like itself ap peared was over three billion years ago probably sometime between the earth's one-billionth and two-billionth birthdays.
The next great event in the story of the earth was the development of the green pigment chlorophyll. With chlorophyll, living cells could use the energy of sun light to make food for themselves out of chemicals in the sea. In the process, they added oxygen to the air.
With a better supply of food and grow ing amounts of oxygen, life could develop at a faster rate. By the beginning of the Paleozoic, all the big groups of animals now in existence-except the backboned group, the one to which we ourselves belong-had appeared.
simple plants and a nimals
Throughout the first half of"the Paleo zoic, the leading animals were all inver tebrates-the animals without backbones. Chief among them were trilobites. The time is called the Age of Invertebrates. During it, fishes, the first backboned ani mals, made their appearance. They quickly became so numerous that the middle pe riod of the Paleozoic is called the Age of Fishes.
The Age of Fishes was followed by the Coal Age. The Coal Age could just as well be called the Age of Amphibians, for am phibians were the leading animals. From them the reptiles sprang. By the time the Paleozoic ended, the reptiles had pushed the amphibians aside. This is the time when the dinosaurs appeared and became the rulers of the earth.
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How
We Find
Out
The last dinosaurs died more than 60million years before there were any people on the earth. Of course, then, no written records have come down to us from dino saur days to tell us about these fantastic creatures. However, we know much about them and other living things of long ago, because scientists have learned to "read stories" in rocks.
All the traces found in rocks of the living things of past ages are called fossils. Shells, teeth, and bones are common fos sils. The very first dinosaur fossils found were teeth.
The men in the picture below are digging out the bones of a dinosaur. The bones are petrified. Petrified means "turned to stone." The bones were petrified in this way: When the dinosaur died, it sank to the bottom of a pond. In time, its body was covered with mud. The soft parts rotted away, leaving only the bones. Little by little, minerals from the water filled up every tiny space in the bones. Then the water took away, bit by bit, the bone ma terial itself, leaving minerals in its place. At last the bone was all stone, and the layer of mud around it had turned to a layer of solid rock.
By far the greatest number of fossils are found in regions where many layers of water-made rock are piled one on top of another. Each layer is likely to be a chapter in the story of the living things of past ages. It is easy to understand that, if the layers of rock in a region have not been disturbed, the oldest rocks are at the bottom, the newest on the top.
No one could count on having much success as a fossil hunter if he went out
to the middle of a field and dug down to the layers of rock below. Fossil hunting is easiest where streams have done some of the digging needed. On steep valley slopes, a fossil hunter cannot depend on looking at a rock layer and seeing what fossils are to be had for the digging, but often a shell or the end of a bone may stick out and show that there are fossils to be had.
Signs of fossils are easier to sight in arid regions, where the ground is almost bare, than in regions of grass and trees. The badlands in the western part of the United States and Canada, for example, have given up great numbers of dinosaur bones and other fossils.
Also numerous in many fossil beds are dinosaur footprints. The boy pictured is resting his feet in the footprint of a huge dinosaur. The footprint is more than a yard long. Picture a giant dinosaur lum bering along the muddy bank of a pond
some 150 million years ago. Since the creature weighed many tons, its feet made deep footprints in the soft mud. By chance, this footprint was not disturbed. As cen tury after century went by, the mud changed to solid rock. How amazed the little boy would be if the monster that made the print should suddenly appear!
Perhaps you have made a plaster cast by pouring wet plaster into a mold and letting it harden. Some dinosaur fossils are casts of dinosaur footprints. Suppose a small dinosaur left a footprint in a mud dy bank. Later, while the footprint was clear and sharp, a thick layer of sand was washed up over the mud. It filled in the footprint and covered the ground all around it. In time, both the mud and the sand were cemented into solid rock. When, long afterward, the layer of sandstone and the layer of mudstone were split apart, the imprint of the dinosaur's foot still showed in the mudstone, and, rising up from the sandstone, there was a cast of the foot.
dinosaur leg bone
dinosaur skeleton
dinosaur cast footprints
For years after the first fossils of dino saurs were discovered, scientists could only guess that dinosaurs, like most reptiles, laid eggs. Then some petrified eggs were found alongside skeletons of the dinosaurs that laid them. Though others have since turned up, eggs are not common fossils.
Locating a fossil is often only a small part of getting it. If a hunter has found, for instance, the bones of a giant dino saur, he has ahead of him the long, hard task of digging them out of the rock they are in. He may need shovels, hammers, picks, or even dynamite to loosen them. A big bone may haveybeen broken at some time during the ages, and getting it out 8
of the rock may mean getting out many small pieces, perhaps hundreds. The fos sil hunter may have to use pieces of wood and iron and even bandages to hold the parts of a broken bone together. If the bone is not too large, he may cover it all with plaster.
Large fossils may be so heavy that they are hard to handle. The petrified skull of one great dinosaur, when packed and ready to be shipped to a museum work shop, weighed over 3,500 pounds!
Building the fossil bones of an ancient animal into a skeleton may take months of work. Bits of rock remaining on the bones must be chipped away, and then
the bones must be sorted according to where they belong and fastened in place. A framework of metal tubing, or "plumb ing," supports the skeleton.
If the animal is one that is new to scientists, there is always the question of whether all its bones are there. An artist who drew pictures of giant dinosaurs when only a few had been discovered always showed the dinosaurs coming out of a pond or group of trees, so that the end of the tail did not show, in case some tailbones might be missing.
From the skeleton of an ancient ani mal a great deal can be told about the animal-its size, how it moved about, whether it ate plants or meat, how big its brain was, and what animals of today it was most like. Knowing how today's animals are built and how and where they live helps scientists to know about the animals of long ago.
The story of the living things of past ages still has many gaps in it, but there is always a chance a fossil will turn up that will fill one of those gaps. Not many years ago, a fossil hunter found the bones of a duck-billed dinosaur in Mexico, near the Pacific coast. Until then, no trace of that kind of dinosaur had ever been found so far west in North America. You yourself may someday add something to the story of dinosaurs.
Oviraptor
The Age of Reptiles
It is easy to see from the chart how the Mesozoic Era earned the name of Age of Reptiles. From early reptilian begin nings back in the Coal Age, there had arisen, by. the time the curtain went up on the Mesozoic, six major groups of reptiles, all of them destined for stardom. Each of the six groups is shown in a dif ferent color on the chart. It was in the Triassic, the first act of the great reptile show, that the dinosaurs made their bow. As the chart shows, there were two separate lines of dinosaurs. The two were about as closely related as horses and cows. Their common ancestor, the theco donts, also gave rise to the pterosaurs, or flying reptiles, and to the crocodilians. Birds, too, descended from the theco donts, but, through the ages, the birds be came so different from their reptile rel atives that they are put in a class by themselves.In the second and third acts-the Ju rassic and Cretaceous periods-the reptiles were at their peak. Dinosaurs ruled the land. Other reptiles ruled the seas. In the air, the pterosaurs were, for the most part, without serious rivals. By the beginning of the Cretaceous, only one group, the mammallike reptiles, had already left the stage. Before it did, however, it had given rise to still another big class of ani mals-the mammals.
When the curtain went down on the Mesozoic, it went down on the dinosaurs and most of the other reptiles that had shared the limelight with them. Of the reptiles that are left alive today, most play minor roles.
Strangely enough, it was an egg that started the Age of Reptiles. The eggs of 10 c( 1:111: w u
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the fishes and the amphibians are laid in water, to keep the eggs from drying out, and the baby animals that hatch from them are water animals. The egg of a reptile is a land egg .. It is a private hatch ery pool for the little reptile growing in side it. Because of such eggs, the reptiles were free to exploit the land.
Like the fishes and amphibians, the reptiles are cold-blooded. They cannot regulate their body temperature the way the warm-blooded birds and mammals
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'(' o'\'o 1>-\)"''t Antarcticado. Instead, their bodies are the same temperature as ·the air or water around them. Today, only small reptiles live where the winters are very cold. Yet fossils from far northern lands, among them the island of Spitsbergen, tell that large dinosaurs once lived there. Others, from Antarctica, reveal that good-sized reptiles used to live on that now-frozen continent at the bottom of the world.
Clearly the climate in these widely separated regions of the earth was milder
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than it is now. It is not surprising, then, that in that balmier time the dinosaurs were widespread.
But how had dinosaurs, which are land animals, managed to travel between re gions separated by hundreds-in some cases thousands-of miles of sea? Dino saur fossils like some found in Europe, for instance, tum up in rock layers of Australia and Madagascar, both remote from all other land.
Some geologists have said that, in such cases, the animals must have crossed the sea on land bridges no longer in existence or by island hopping-going from island to island, that is, and so covering long stretches in short stages. Others have ar gued that the animals might have been able to swim long distances.
Many scientists, however, have for years had the idea that the answer lies in the location of the continents. They say that the continents were not always spread out over the globe as they are now but, in stead, over millions of years, drifted to their present, separated positions. At the start of the Mesozoic, these scientists say, all the lands of the earth were clumped to gether in one huge supercontinent they call Pangaea.
The maps show how they think the continents came to be where they are now. In the Triassic, the supercontinent began to split apart. North America and Eurasia formed one large northern continent:
Laurasia; and the four southern continents, together with India, formed a southern one : Gondwana. The Jurassic saw Ant arctica separate from Africa and South America, and India start drifting north ward. By Cenozoic time, both South Amer ica and Madagascar had broken away from Africa, but it was not until well into
the Cenozoic that North America and Greenland parted completely from Eu rope, India jammed into Asia, and Austra lia separated from Antarctica.
Studies made of the ocean floors bear out the idea of continental drift. So does evidence, found in the rocks, of apparent wanderings of the earth's north magnetic pole. So, too, do such fossil finds as those of the mammal-like reptile Lystrosaurus, with its plant and animal neighbors, in rock layers in Antarctica;_ these layers are of the same age as those containing sim ilar fossils in South Africa. Today most scientists agree with the idea of conti nental drift.
The Rul i ng Repti les
Saltoposuchus
You have already seen, on pages 10 and 1 1, that two of the branches on the big center limb of the tree diagram rep resent the dinosaurs, and the other two branches, the flying reptiles and the croco dilians. These four groups, together wit
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the thecodonts from which they came, are known as the archosaurs, or ruling reptiles. The name comes from archos, a Greek word meaning "ruler."Saltoposuchus is one of the best known of the thecodonts. This early ruling rep tile is often spoken of as the grandfather of the dinosaurs. Like many of its famous dinosaur descendants, Saltoposuchus ran or leaped about on two long, strong hind legs, its muscular tail streaming out be hind. The long, heavy tail balanced the forward tilt of the animal's body.
Looking at Saltoposuchus as it darted about in search of a small lizard or drag onfly to get -its teeth into, you probably wouldn't have dreamed that it would one day have "grandchildren" the length of a locomotive and the weight of more than half a dozen elephants. Saltoposuchus was about the size of an undernourished, unfeathered turkey gobbler.
14
The most specialized of the thecodont descendants-except, of course, for the birds-were the pterosaurs. This group developed wings-wings quite different from those of birds-and took to the air. The pterosaurs may even have been some what warm-blooded.
The least specialized were the croco dilians, though a few, in the course of time, developed special adaptations for life in the sea .. Some crocodiles of today, too, can live in salt water. The croco dilians are the only ruling reptiles that survived the "time of the great dying" at the close of the Mesozoic.
Of ruling reptiles, the superstars, of course, are the dinosaurs. The creatures are fascinating partly because of the enor mous size many of them reached and partly because they dominated the earth for so long and then disappeared com pletely. Why these animals lived so long and. then disappeared is a question scien tists have never been able to answer.
The "X-ray" views of the hip joints of the dinosaurs in the pictures show the chief distinction between the members of the two big dinosaur groups. The lizard hip dinosaur group (Saurischians), repre sented here by Gorgosaurus and Cam arasaurus, is the one to which most of the dinosaurs we think of as typical belong the giant plant eaters and meat eaters. All the meat-eating, or carnivorous, dino saurs belong here. The bird-hip dinosaurs (Ornithischians), represented in the pic tures by Camptosaurus and Stegosaurus, were 100 percent plant-eating, or herbiv orous. Both groups included dinosaurs that walked on four legs and those that walked on two.
For nearly 165 million years, these four groups otreptiles ruled the earth. Of these, only the crocodi lians survived. Shown above is an a l l igator, a li"ving relative of this ancient group.
Gorgosaurus
Camptosaurus
Stegosaurus
Crocodilians
Alligator
Pterosaurs (flying reptiles)
Lizard-Hip Dinosaurs
Camarasaurus
•
Brachiosaurus
1 6
Giant Plant Eaters
This picture introduces you to the giant of giants, Brachiosaurus, the biggest ani mal, so far as scientists have found, that ever walked the earth. The only bigger
animals known-today's
g
iant whaleslive in the sea. Brachiosaurus, however, with a weight of 50 tons and a length of 80 feet, approached half the weight of the biggest whale-the big blue whale, or sul phur-bottom-and measured almost as long. In height, Brachiosaurus outranks all other animals, past and present. With its head held high it stood over 40 feet tall. The big reptile could easily have looked over the top of a three-story
build-Plateosaurus
ing-supposing there were such a building 150 million years ago.
The name Brachiosaurus means "arm lizard." The name comes from the fact that this dinosaur did not follow the usual dinosaur pattern of having front legs short er than the hind legs.
Although Brachiosaurus would certainly have been frightening to meet, it was not one of the dinosaurs that earned for them the name "terrible lizard." Brachiosaurus was a slow-moving, harmless creature that ate nothing but plants. It was also slow witted. In spite of its enormous size, the big plant eater had a brain smaller than a kitten's. In proportion to its weight, Brachiosaurus got by with fewer ounces of brain than any other back boned animal we know about.
The group of giant plant eaters to which Brachiosaurus belonged are often called the amphibious dinosaurs, because most scientists think they spent much of the time in swamps and ponds, where the water helped to hold up their heavy bodies. Even though their legs were like tree trunks, the great weight of these dinosaurs must have been a tremendous burden.
Yaleosaurus
Brachiosaurus, with its long neck and long front legs, could stand in deep water and still have its head out of water. Actually, it needed only the top of its head clear of the water, for its nostrils were located in a bony crest at the top.
Brachiosaurus and its fellow waders had
·teeth suitable for eating soft plant food. They must have spent most of their days cropping water plants, for their enormous bodies needed tremendous amounts of food. Clearly the creatures were well fit ted for such a life, for they survived, in one part of the world or another, for 100 million years! Fossils of Brachiosaurus have been found in such widely separated areas as North America, Europe, and Af rica. Skeletal remains thought to be its bones have been found in Asia, too.
Yaleosaurus and Plateosaurus were forerunners of Brachiosaurus and the other giant plant eaters. They were not nearly as large as those later giants, but they certainly were not small. Plateosaurus was about 20 feet long, Yaleosaurus about 8 feet.
Both of these early dinosaurs could walk on just their hind legs as well as on
Camarasaurus
all fours. Probably they stayed on all fours, except when they were in a hurry. Their teeth were fitted for eating plant food rather than meat.
In the picture, Y aleosaurus is brown and Plateosaurus green. Y aleosaurus has stripes across its back, while Plateosaurus has a mixture of stripes and splotches. Actually, no one knows what color either these or any other dinosaurs were or what markings they had. Artists can only guess, from the color and markings of modem reptiles. Common reptile colors today are brown and green. Markings, moreover, help today's reptile� to hide from meat eating enemies. It is a good guess that these two dinosaurs were often hunted by meat eaters of the time and that they had
1 8
markings o f one kind or another that helped to conceal them among the shad ows and plants.
Just as Brachiosaurus was the giant of the amphibious dinosaurs, Camarasaurus was the pygmy. It was only about a third as long as Brachiosaurus. Even so, it weighed many tons and followed the same
general body pattern-that is, a big body, a long neck and tail, and a small head with a tiny brain inside. The skull of Camarasaurus has been compared with that of a bulldog. It was short, and the jaws were heavy. The teeth in the big plant eater's jaws, however, were not much like a bulldog's.
Diplodocus, another record holder, was the longest of the amphibious dinosaurs. From the tip of its jaws to the end of its tail, Diplodocus measured nearly 100 feet-one-third the length of a football field or, put in another way, the length of seven or eight elephants marching trunk to tail. Imagine Diplodocus in such a parade!
Diplodocus was far more slender than big Brachiosaurus. It weighed a mere 25
tons, give or take 5 tons.
The name Diplodocus means "double beam." The dinosaur was given the name because it reminded scientists of a kind of scale for weighing-a balance with beams. Its very long neck just about bal anced its very long tail.
On its feet Diplodocus had broad pads, much like those of an elephant. Some of the toes were clawed. Probably they kept it from sliding around in the mud. All
Diplodocus
the amphibious dinosaurs had feet very much like those of Diplodocus.
Like Brachiosaurus and the other giant plant eaters, Diplodocus had only a tiny brain. Along the spinal cord, however, these dinosaurs had knots of nerve cells, called ganglia, that controlled the legs and tail. When we wish to move any part of our body, a message must go along nerves to the muscles in that part of the body. Suppose, as you are washing your hands under the faucet, the water suddenly gets too hot for comfort. A pain message travels along nerves from your hands to your brain. Then a message goes back from your brain to the muscles of your hands, and you pull your hands away. It all hap
pens almost as quick as a wink, because the messages to and from your brain have only a short distance to travel.
Suppose, however, an enemy grabbed Diplodocus by the end of its long tail. It would take a large part of a minute for the danger message to go the 90 feet or so to the dinosaur's brain and for the return message to tell the muscles to lash the tail at the enemy. In that time, the end of the tail might be gone. Having a "helper brain" (ganglion) closer to the tail and legs was certainly an advantage.
Diplodocus and Camarasaurus may often have come face-to-face with Brach iosaurus, for they, too, were common in what is now North America. Another giant whose bones are found with theirs is Brontosaurus, the best known of all the big plant eaters and one of the first to be discovered. Brontosaurus, as you can see, looked much like Camarasaurus, but Brontosaurus was over twice the length of Camarasaurus and weighed many tons more. However, it lacked some 15 feet of being as long as Diplodocus and some 15 or 20 tons of being as heavy as the giant Brachiosaurus.
The name Brontosaurus means "thunder lizard." The scientists who first found and
20
put together the bones of its skeleton thought that when so big a creature walked about, the ground shaking underfoot must have rumbled like thunder. The big foot print pictured on page 6 records one of its thunderous footsteps. It is easy to see that the great dinosaur would have crushed any small animal it stepped on. As with all the giant plant eaters, Brontosaurus, aside from sheer bulk, had no weapons other than its long tail for protection against enemies. The whiplash from such
Brachiosaurus
Diplodocus
a tail, however, would really be something to watch out for.
Some of the reptiles of today are long lived. The giant tortoise, in fact, holds the record for long life among animals. It may live to be 150 years old. Scientists cannot tell how long dinosaurs lived. Some say that Brontosaurus may have lived to be 1,000 years old. Others believe that 200, or at most 300, years is a better guess. Still others say less than 100.
It would be easier for scientists to get an idea of how fast the big dinosaurs grew and how old they lived to be if there were fossils of newly hatched and young and middle-aged �pecimens. Almost all the skeletons of the giant plant eaters,
unfor-Brontosaurus
tunately, are of adult forms. It would seem that these huge dinosaurs, unless a whole community of them were wiped out and buried in some natural catastrophe, ordi narily were either eaten up by enemies when young or lived to adult size.
The giant plant eaters you have just read about were all lizard-hips. For mil lions of years these giants had the swamps and lakelands of the Mesozoic pretty much to themselves. In time, however, they were largely replaced, at least in the northern continents, by big plant-eating dinosaurs of the bird-hip group. But nei ther those later dinosaurs nor any other land animals we know about have come close to matching them in size.
Podokesaurus
Lightweights
After reading about such giant dinosaurs as Brontosaurus and Diplodocus, you may be shocked to learn that the four small reptiles pictured on these two pages are also dinosaurs. They were all far from gigantic. These slim, long-legged dinosaurs represent a group often spoken of as "lightweights."
Like the giant plant eaters, the light weights were lizard-hip dinosaurs. But these small lizard-hips walked or ran on their hind legs. That is, they were bipedal. Their front legs and feet served as arms and hands. In the main, they were meat eaters, and their long legs suggest they could move fast, as meat eaters often have to do to catch the food they need.
Podokesaurus, the "swift-footed lizard," was an early dinosaur. Its gigantic cous ins would not appear for many millions of years. However, another forerunner of the giants, 20-foot-long Plateosaurus, and other dinosaurs much like it, were already present. They certainly dwarfed speedy little Podokesaurus, which was less than a yard long. Of course, so small a meat 22
eater was hardly a threat to creatures the size of Plateosaurus. Probably it ate most ly little lizardlike reptiles.
· Compsognathus lived several million years after Podokesaurus, during the great days of Brontosaurus and its fellows. No
Compsognathus bigger than a rooster, it was even smaller than Podokesaurus. It probably ate other small reptiles, just as Podokesaurus did, but it had a more varied diet; by this time there was a good supply of small furry animals-mammals-scurrying about.
Among still later lightweights were those known as ostrichlike dinosaurs. Oviraptor and Ornithomimus were two of them. Ornithomimus means "bird mimic."
Another name for the same dinosaur is Struthiomimus-"ostrich mimic." Ovi raptor's name means "egg robber." This dinosaur was only about a yard long. Ornithomimus measured about 8 feet.
With their long necks and legs and their small heads, these dinosaurs did in deed look much like ostriches. Like os triches, too, they had horny bills and no teeth. Of course, they differed greatly from ostriches in having long tails and not having feathers. Moreover, they had arms and hands instead of wings.
It seems strange for meat eaters to be toothless. The answer, scientists think, is that these members of a meat-eating line had probably become chiefly egg eaters. They could handle the eggs easily with their hands. They could peck holes in the shells with their bills. They did not need teeth for chewing the contents of the eggs. There were insects they could eat, too.
Sometimes, apparently, these egg steal ers were caught in the act. In one of the nests of petrified dinosaur eggs, scientists also found the crushed skull of a supposed egg-stealing dinosaur.
Ornithomimus
Oviraptor
As you may remember from the reptile tree on page 11, the lightweights are on the same branch of lizard-hips as the giant meat eaters. Those big brothers of theirs, which stalked the land through much of the Age of Reptiles, were the truly terrible dinosaurs.
Allosaurus
Giant Meat Eaters
The living things of every natural region of the world can be thought of as a pyramid. At the base of the pyramid are green plants. Without green plants, there could not be any animals, because the food of all animals can be traced back to green plants. Above the green plants are the plant-eating animals-some big, some small. Another name for them is herbivor�s. Above the plant eaters are the meat eaters-the carnivores. Again, some are big and some are small. The biggest and fiercest of the meat eaters of a region is known as the top carnivore.
In a large part of Mrica today, the top carnivore is the lion. It feeds on zebras, giraffes, and antelopes, all of which eat grass and other green plants.
In the days of the dinosaurs, the liv ing things of the different regions formed 24
similar pyramids. The plants were not the same as those of today, but they furnished food for the plant eaters, just as modern plants do. Among the leading plant eaters on land were such giant dinosaurs as Camarasaurus, Brontosaurus, Diplodocus, and Brachiosaurus. The leading carnivores were huge meat-eating dinosaurs. No one would question the choice of the name dinosaur for these reptiles. They were truly terrible.
Allosaurus, the "leaping lizard," pic tured here feasting on some big reptile it has killed, was one of those giant meat eaters. These huge and terrible dinosaurs belong to the same big dinosaur group, the lizard-hips, as the giant plant-eating dinosaurs.
Allosaurus's victim in the picture could well have been Brontosaurus. Bones of
the thunder lizard that show the marks of Allosaurus's teeth have been found. Think of having 30 tons of fresh meat from a single kill! To eat it all, Allosaurus would have had to go back time after time to feed.
Allosaurus was not as big as most of the giant plant eaters it preyed on. Even so, it stood some 15 feet tall as it stalked or leaped about on its strong hind legs. The ponderous plant eaters had no chance of escaping Allosaurus by running away. They weren't fast enough. Perhaps only by moving into deep water were they safe from its claws and teeth.
The front legs of Allosaurus were much smaller than the hind legs. They were of no use in walking, but the three "fin gers" on each "hand" were armed with long, sharp claws. The hind feet, too,
were clawed. They were much like the feet of a giant bird.
Allosaurus clearly did not follow the small-head pattern of the giant plant eat ers. Its skull was 2lh feet long. Its mouth, like the mouths of today's snakes, opened very wide, so the creature could swallow great chunks of food. As you know, the plant eaters had teeth that could chew only soft plants. In contrast, the teeth of Allosaurus were long and strong and as sharp as knives. They were a great help in killing prey and stripping the meat off the bones.
Besides the giant plant eaters, there were plenty of smaller dinosaurs and other reptiles to furnish meals for Allosaurus and its meat-eating relatives. We can guess that giant plant eaters were often saved, for the time being, by the presence
Skull and head of Tyrannosaurus
of some smaller prey that could be cap tured without a battle. Of course, the bat tles between Allosaurus and the big plant eaters we can only imagine. We know about these fights only from such signs found in the rocks as broken bones and missing teeth.
If you knew about all the big animals of the past and could choose the one you would least like to meet today, the one you would probably choose is the dino saur Tyrannosaurus, the "tyrant lizard." This dinosaur is believed to be the largest carnivore that ever walked the earth. It was probably the fiercest, as well. Just imagine a huge, man-eating reptile, four times as tall . as you, coming toward you on its hind legs, eyes glaring and jaws agap e and all its big, evil-looking teeth showing clearly, and you will have some idea of what Tyrannosaurus must have been like.
26
The whole name of this most terrible of terrible reptiles is Tyrannosaurus rex. The rex in the name means "king." The huge meat eater was "king of beasts" 100 million years ago, just as the lion is said to be today.
Tyrannosaurus lived at a later time than Allosaurus. It lived in the Cretaceous period, while Allosaurus had its heyday in the Jurassic. The family of Cretaceous dinosaurs to which Tyrannosaurus be longed are often called deinodonts. The word means "terrible teeth." Gorgosaurus, one of the dinosaurs pictured on page 15, was a member of the family. The name deinodont, in fact, comes from one of the many names that Gorgosaurus has been given by scientists.
Tyrannosaurus was much larger than Allosaurus. Its body measured nearly 50 feet from the top of its head to the tip of its tail. Allosaurus was only 35 feet long. Tyrannosaurus stood nearly 20 feet tall and therefore would have towered over Allosaurus. Its skull was twice the length of Allosaurus's. Incredibly, it could open its mouth a full 4 feet.
Like Allosaurus, the tyrant reptile was bipedal. All the big meat eaters were. Its front legs were even smaller and weaker than those of Allosaurus. Instead of three strong fingers armed with stout claws, like those of Allosaurus, Tyrannosaurus had only two feeble fingers, with claws that could not have been any help in either fighting or tearing off chunks of meat. The short front legs weren't even long enough to reach the dinosaur's mouth. It is hard to see how they could have been of any use at all. But what difference did weak front legs make to Tyrannosaurus, when it had powerful hind legs and feet, with toes ending in
Tyrannosaurus
long curved claws like an eagle's, and huge j aws bristling with daggerlike, saw edged teeth six inches long!
Even though the skull of Tyranno saurus was huge, you can see from its shape and the size of the jaws that there was not much room for a brain. The king of the reptiles could not have been much more intelligent than its small-brained plant-eating relatives.
By the time Tyrannosaurus appeared,
the giant plant eaters were not as numer ous in its part of the world as in the past. The plant eaters that Tyrannosaurus preyed on were mostly of other kinds. The picture shows the big killer in pur suit of the ostrichlike Ornithomimus, one of the swiftest of the lightweights. In spite of the speed of Ornithomimus, Tryrannosaurus, with its longer legs and longer stride, couldn't have had much trouble catching and eating it.
Plated Dinosaurs
With big meat eaters such as Allosau rus and Tyrannosaurus around, it is not surprising that some of the plant-eating reptiles developed protective armor. Among those that did were the plated dinosaurs. As you know from the reptile tree, the plated dinosaurs belong to the bird-hip branch of dinosaurs. They were no more closely related to the giant plant eaters of the lizard-hip group than to the giant meat eaters.
You have already twice met the best-known plated dinosaur, Stegosaurus. Stegosaurus lived in the days of Allosau rus. Many pictures have been painted of imaginary battles between the two.
Stegosaurus was from 18 to 25 feet long, and it weighed 7 or 8 tons-much ·more than a big elephant weighs. In
con-Stegosaurus
28
trast w
�
th its meat-eating enemies, itwalked on all fours. Its hind legs were much longer than its front ones. The very short front legs held the big reptile's head close to the ground. Its neck, more over, was so short that it could not lift its head high to look around as the giant plant eaters could. With so little chance of seeing enemies until it was face-to face with them, it really needed armor to protect it.
As you can see, its armor consisted mainly of two rows of bony plates ex tending down its back. In the middle of the dinosaur's back, the plates were about two feet tall. They made Stegosau rus about twice as tall as a man. On its tail it had four great spikes. Because of its plates and spikes, Stegosaurus looked
Scelidosaurus
.fearsome, but its armor served only as protection. The big dinosaur had no weapons except its spiked tail, and that was used for defense rather than attack. It had teeth, but they were all in the back of its mouth and were good only for chewing.
The head of Stegosaurus was ridicu lously small. It was small even for a plant-eating dinosaur. Of course, there was not much room in it for a brain, so what brain it had was very tiny. In common with many other dinosaurs, it also had knots of nerve cells on its spinal cord. The largest was between its hips.
This ganglion, in fact, was about twenty times as large as the creature's brain.
Sixty years or s9 ago, a newspaper columnist wrote a jingle about Stegosau rus which became very well known. In it the writer said that the dinosaur was very fortunate in having two brains. He goes on to say:
As he thought twice before he spoke, He had no judgments to revoke, For he could think without congestion
Upon both sides of every question.
Clever as the jingle is, it isn't at all true. Stegosaurus was not an intelligent ani mal. It didn't do any real thinking with its brain, let alone with the big ganglion near its hips, the chief purpose of which was to control the back legs and tail.
No other plated dinosaurs have been found that had as well-developed plates as those of Stegosaurus. Those of 13-foot Scelidosaurus, one of the earliest known of all the bird-hip dinosaurs, for in stance, were far less spectacular.
In their time, the plated dinosaurs
....,..iia� ... were common around the world. Howev
er, they were the first big group of dino saurs to disappear.
An kylosaurus
Ankylosaurus
Giant Tortoise
Armored Di nosaurs
The armored dinosaurs filled the sameniche in the days of Tyrannosaurus that the plated dinosaurs filled when Allosau rus was a top carnivore. Ankylosaurus is typical of the group.
In its picture, Ankylosaurus, because of its flatness and its spines and spikes, may remind you of a homed toad. A homed toad is really a lizard and is, therefore, a very distant relative of An kylosaurus. If you could see both ani mals alive, however, you certainly would not confuse them. A homed toad is only about 6 inches long and 2 inches high. Ankylosaurus measured some 17 feet in length and 4 feet in height. A homed toad, moreover, is not a plant eater, as Ankylosaurus was, but a meat eater. Be sides, in spite of its small horns and
30
spines, a horned toad's armor cannot compare with an armored dinosaur's.
The armor of Ankylosaurus was much more like that of Boreostracon, an ex tinct mammal that lived in North and South America in the Ice Age. They both had shields of bony plates that cov ered their backs, and smaller shields that almost covered their faces, and both had tails like war clubs. Except for some of the turtles, Ankylosaurus was the most fully armored reptile of all time. It could not pull in its head and legs to get them undercover the way a giant tortoise can, and its sides were not as well protected, but it still deserved to be called, as it of ten has been, an armored tank.
The plates of bone that formed the shield on the back of Ankylosaurus had
..
bony bumps that made for better protec tion. Along its edges, the shield had bony spikes extending outward. The tail, which was protected by rings of bone, ended in a ball of solid bone.
Ankylosaurus needed its coat of mail, for it was a slow-moving creature, with legs so short and a head so close to the ground that it had an even poorer chance of seeing approaching enemies than Stegosaurus had. It had no combat weapons except its tail. Its teeth were weak and good only for eating plants. The teeth, moreover, like those of Stego saurus, were all in the back of its jaws, not in front, where teeth good for biting need to be. Its tail, however, must often have helped Ankylosaurus fight off ene mies. One swing of it might well have persuaded a meat eater to hunt for its dinner somewhere else. If you have ever seen a big lizard, such as an iguana, fighting off an enemy with its tail, you know what a powerful weapon a lashing
Polacanthus
tail can be. The tail club of Ankylosau rus must have made its tail truly lethal.
The way the bony plates in the armor of Ankylosaurus were fused with bones in its skeleton gave the dinosaur its name. Ankylosaurus means "fused liz ard," or "stiff lizard."
Fossils of Ankylosaurus have been found only in North America. Other armored dinosaurs, however, were scat tered far and wide over the earth. Fossils of several different kinds, much like Ankylosaurus, have been found in Afri ca, Asia, Europe, and South America.
Polacanthus, the early armored dino saur pictured below, is known from fos sils found in England. This dinosaur,
only 14 or 15 feet in length, was not
quite as large as Ankylosaurus. It was not as well armored as Ankylosaurus, either. But with all those spines down the sides of its back, it could not have been easy prey for even the hungriest giant meat eaters that came its way.
Parasaurolophus
Duckbi l ls,
Boneheads, and Parrot Beaks
Fortunately for Tyrannosaurus and the other big meat-eating dinosaurs of its time, there were plenty of plant-eating dinosaurs that made far easier prey than the plated and armored ones. Among them were the duckbills, big dinosaurs of the bird-hip group. The duckbills were common in the days of Tyrannosaurus as common as deer are in ours.
The duckbills were descendants of Camptosaurus, a 7-foot bipedal dinosaur that, in ah earlier period, had browsed the forests alongside Stegosaurus. Except in size, they were still very much like their small ancestor. One picture on page
15 shows Camptosaurus.
3 2
All three dinosaurs pictured here are duckbills. One of them, Trachodon, is so famous that many people think of it as the only duck-billed dinosaur.
Trachodon was about 30 feet long. It
could walk on all fours, but it often walked on just its heavy hind legs. It
stood about 1 8 feet tall, almost tall
enough to look Tyrannosaurus straight in
the eye-if, that is, it would ever have got
that close to the king of the dinosaurs.
Trachodon spent most of its time in marshes and sluggish streams. It ate plants growing in the water and along its edges. Like all the duckbills, it had a broad, flattened bill much like a duck's.
lambeosaurus
In the front of its jaws, it had no teeth. However, in the back, it had rows and rows of peglike teeth good only for grinding up its food. Its teeth were crowded together, like the stones in an
old-fashioned cobblestone pavement.
The dinosaur's name of Trachodon means "rough tooth." When we lose one of our baby teeth, a tooth that has been hidden in the jaw takes its place. Each of Trachodon's teeth could be replaced sev eral times. Altogether, Trachodon had many hundreds of teeth.
To go with its ducklike bill, Trachodon had webbed feet. There were three toes on each hind foot. Strangely enough for
Trachodon
a reptile, each toe ended in a small hoof. On each front foot, or hand, Trachodon had three fingers with hooves and one very small finger without either a hoof or a claw.
Although Trachodon must have walked about on shore part of the time, either on two feet or on four, its powerful hind legs, with their webbed feet, doubtless made for greater speed in water than on land. Its big crocodilelike tail must have helped, too, in pushing it through the water faster.
Scientists have found in rocks casts of Trachodon's skin-casts made from the imprint of the skin in the wet mud. They
show that it was covered with small scales. They indicate also that the skin had different color patterns but, of course, give no hint of what the different colors were.
Except for their strange-looking skulls, Lambeosaurus and Parasaurolophus were very much like Trachodon. Para saurolophus had a long hornlike projec tion growing from the back of its head. Lambeosaurus had a crest on the top of its head, with a long prong going back from the crest. Lambeosaurus was named after a famous Canadian geologist, L. M. Lambe. Parasaurolophus means "like a crested lizard."
Shown along with Trachodon in the picture on this page is Corythosaurus,
Corythosaurus
another duckbill with a big crest on its head. The name Corythosaurus means "helmeted lizard." The crest looks a little like a rooster's comb, but, unlike a comb, it was made of bone.
No one is certain about how these crests of various shapes were helpful. Inside them there were air tubes. Per haps they stored air which the dinosaur could somehow use when its head was underwater. Perhaps they were simply traps to keep water from getting into the dinosaur's lungs. They may even have had something to do with smell. No one really knows.
There were duckbills of many other kinds. The four you have just read about lived in North America, but there were
duckbills in other parts of the world as well. Many fossils of them have been found in Europe and Asia.
None of the duckbills had any kind of protective armor. Since all of them were at home either in ponds and swamps or on land, their chief way of saving them selves from the . truly terrible dinosaurs of the time may well have been, as with the giant plant eaters, to retreat into the safety of the water.
Pachycephalosaurus was not a duck bill. Rather, it belonged to a closely related family of dinosaurs known as boneheads. The name Pachycephalosaurus means "thick-headed lizard." It is certainly suitable, for over the creature's tiny brain there was a several-inches-thick dome of solid bone. Pachycephalosaurus had not only a great dome of bone over its brain but also strange bumps and spikes of bone decorating its head and face. Certainly it would never have taken a prize in a beauty contest.
Pachycephalosaurus spent much of its time in the water and ate water plants, just as the duckbills did. It was not as large as most of the duckbills, being only 20 feet or so long. Like many of the
Pachycephalosaurus
duckbills, Pachycephalosaurus lived in North America.
Psitticosaurus, another duckbill rela tive, lived in eastern Asia. Its beak was much more like a parrot's than like a duck's. The name Psitticosaurus means "parrot lizard."
Psitticosaurus was not very big. It measured only 4 feet in length. Although it was so small,- scientists consider it important, for, they believe, the parrot beaks were ancestral to-the great homed dinosaurs.
Psitticosaurus
Protoceratops
Horned Dinosaurs
Protoceratops was, in a way, the beginning of the end for the dinosaurs. It was one of the first of the horned dino saurs, the last dinosaur group to appear. Protoceratops means "before-horn face." Though it was a horned dinosaur, Proto ceratops had no horn. But it did have a big bony frill that protected its neck, just as other horned dinosaurs had. It had also the stout parrotlike beak that the horned dinosaurs inherited from their parrot-beak ancestors.
Protoceratops was only about 6 feet long-small for a horned dinosaur. Like all bird-hip dinosaurs, it ate plants. In addition to teeth in the back of its jaws, it had four tiny ones in the front. Later horned dinosaurs had no front teeth and were much larger.
Protoceratops lived in eastern Asia. It has won fame chiefly because of its eggs. The first dinosaur eggs ever discovered along with the fossil bones of the dino saur thought to have laid them were Pro toceratops eggs. They were found in a desert region of Mongolia. The eggs, now petrified and brown, had been laid
3 6
in a hollow in the sand, just as the eggs of sea turtles are laid today. The mother dinosaur had then covered them with sand, but instead of going away and leaving her eggs, as turtles do, she had
.
apparently stayed nearby to guard them. Crocodiles of today are known to stay near their nests. In one Protoceratops egg that had in some way been broken open sometime before it was ready to hatch, the bones of the baby dinosaur can be seen quite clearly.
Styracosaurus and Monoclonius were two of the later horned dinosaurs. Styra cosaurus means "spike lizard," and Monoclonius "one conqueror." The first of these names comes from the spikes on this dinosaur's big collar, the other from the single weapon, the horn on its nose, of Monoclonius. Both of these dinosaurs flourished in North America.
Styracosaurus was some 15 feet long.
Its weight was about 4 tons. Its head and collar together measured about 6
feet-over one-third the animal's length. The horn in the middle of its nose was
Monoclonius
nearly 2 feet long and 6 inches thick, and some of the spines on its collar were a yard long. The creature was clumsy, slow-moving, and dim-witted. Except for its horn and its fence of spikes, it would have been easy prey for a big meat eater. Its enormous beak, though a powerful cutting tool, was used chiefly for nipping off parts of plants to eat.
Monoclonius measured about 18 feet.
Its fortunes in battle hinged largely on its single weapon, the long, sharp horn on its nose. If the horn failed to be effective, Monoclonius lost the battle.
The huge lizard-hip plant eaters like Brontosaurus and Diplodocus, as you know, are thought to have spent much of their time in the water. So did the duck bills, say the scientists. The horned dino saurs, in contrast, were strictly land ani mals, thus needing their weapons.
Easily the best known of the horned dinosaurs is Triceratops. The name means "three-homed face." Where it came from is clear: Triceratops had a hom over each eye and one on its nose.
Like Styracosaurus and Monoclonius, Triceratops was a North American dino saur. Many, many fossils of it have been found in Wyoming, Montana, and Col orado. Scientists believe that great herds of Triceratops roamed the western plains, just as herds of bison did millions of years later. In fact, the horns of Tri ceratops were so much like those of a bison that the first ones discovered were mistaken for bison horns.
Triceratops was, of course, far bigger than a bison. A full-grown bison is about 1 1 feet long and weighs only about l 1h
Tyrannosaurus
3 8
tons. Triceratops was some 25 feet long
and weighed about 12 tons, nearly twice as much as an African elephant, the larg est land animal of today.
This big homed dinosaur looked more like a rhinoceros than like any other modem animal. But it was about twice as long and weighed several times �s much as any rhinoceros. The hom on its nose was about 3 feet long, roughly the length of the big front hom of a white 'rhinoceros. The two horns over its eyes,
however, were much longer. They mea sured 6 feet or more. Of course, no rhi noceros has a flaring ruff of bone like that of Triceratops.
As in all the bird-hip dinosaurs, the hind legs of Triceratops were much long er than its front legs. The legs were all
sturdy. On its hind feet it had four stubby toes, on which there were hooves. The front feet had five toes each, two of which, the two on the outside, were rather small. The three larger toes had little hooves.
Triceratops and its close relatives, al though they were plant eaters, did not have the huge number of teeth the duck bills had. In the back of both its jaws, Triceratops had only a single row of teeth at each side.
Tyrannosaurus was the great enemy of Triceratops. But Triceratops certainly was no easy mark for the giant meat eat er. The big horned dinosaur was very much a battler. Apparently secure in its defenses, instead of retreating from the enemy, it stood ground and fought fiercely. Its big bony collar gave Tricera tops good protection for its neck, the area where meat eaters often attack their
Triceratops
prey. Its sharp horns could easily rip open the sides or belly of a big, charging meat eater.
The weapons and protective armor of Triceratops, however, were all in front. So long as Triceratops could face the tyrant meat eater, it had a good chance of winning a battle. Even if Tyrannosau rus started to move around Triceratops to attack its side or rear, Triceratops might well be able to slash with a side wise movement of its head. If Triceratops was alone and separated from all other members of its herd, and if a second or third Tyrannosaurus came to join in the battle, the scrappy dinosaur probably had no chance to escape being a meal.
Triceratops appeared near the end of the Cretaceous, the third and the last act of the great reptile show of the Mesozoic. When it disappeared, the days of the dinosaurs were over.
Flyi ng Repti les
The flying dragon of today is a lizard.
In spite of its name, this small lizard does not really fly. Its "wings" are simply flaps of skin that act rather like the wings of a glider. The flying reptiles, or pterosaurs, of dinosaur days really did fly. Pterosaur means "winged lizard."
Although their wings were true wings, the flying reptiles did not look much like They had no feathers but instead were covered with hairy fibers. Their wings were not nearly such good flying devices as a bird's wings are. A pterosaur could not make the many different movements with its wings that most birds can. It could not make any of the smaller movements a bird can make just by moving its wing feathers. A pterosaur's wings were sheets of skin stretched from the very long fourth fingers of its "hands" to its hind legs. The whole wing had to be moved, or flapped, as one piece.
Rhamphorhynchus
But in some ways, the pterosaurs were like their warm-blooded cousins. Scien tists think that they, too, were probably at least somewhat warm-blooded. Many of their bones, as with birds, were hol low. Also, like birds, they had good vision and a poor sense of smell.
Rhamphorhynchus was one of the early pterosaurs. It lived during the Ju rassic, the time of Brontosaurus and Di plodocus. Its name, which sounds like something out of a fairy tale, means "crooked beak." From the tip of that beak to the end of its long reptilian tail,
Rhamphorhynchus was only about
IS
inches long. At the end of the tail, there was a rudder that served much the same purpose as the tail of a kite.
In its jaws, Rhamphorhynchus had many sharp teeth, all pointing forward. Their chief use, apparently, was for spearing fish. Probably Rhamphorhyn chus spent most of its time gliding low over the water, looking for fish. Hollow bones made it light enough for gliding.
Ordinary walking, either on two legs or four, may have been impossible for Rhamphorhynchus. When it was not flying, perhaps it rested by hanging itself up by its claws, much as bats do.
Pterodactylus was a somewhat later pterosaur, though it, too, appeared in the Jurassic. It was the most common flying reptile of the period. The creature ranged from the size of a sparrow to that of a goose. It had only a very short tail, but in other ways it looked much like Rhamphorhynchus. The flying reptile pictured on page 15 is Pterodactylus.
The name Pterodactyl us means , "wing finger." It is a good name for any ptero saur. In fact, pterodactyl is often used interchangeably with pterosaur.
The giant of the pterosaurs was Pter anodon. Like Pterodactylus, it had a very short tail, but it had an enormous an vil-shaped head and very large wings.
The outspread wings measured about 27
feet from tip to tip. On the basis of wing spread, it was the largest flying creature of all time.
Pteranodon had no teeth in its long beak. Its name means "toothless wing." A crest went as far backward from the top of Pteranodon's head as its beak went forward. Perhaps the crest balanced the big jaws and made it easier for the creature to hold its head up. Perhaps it acted as a rudder.
Pteranodon
Like toothy Rhamphorhynchus, tooth less Pteranodon, too, probably spent most of its time soaring out over the sea, looking for fish. It may even have slept in the air. Probably its eggs were laid high up on cliffs, where there were likely to be upward-moving drafts of air.
Pteranodon flourished in the Creta ceous, in the days of Triceratops and Tyrannosaurus, but this big pterosaur disappeared before Tyrannosaurus and Triceratops did. The heyday of the flying reptiles was in the late Jurassic and early Cretaceous. There were birds then, but they were not well enough developed to rival the flying reptiles. By the time Pter anodon appeared, the birds were real rivals, and the flying reptiles finally lost out. The disappearance of Pteranodon was the end of the pterosaurs.
Ichthyosaur
Marine Repti les
As you know, the dinosaurs were landanimals. Not one of them lived in the sea. In their time, though, there were many marine reptiles, among them ichthyosaurs, plesiosaurs, sea turtles, sea crocodiles, and mosasaurs, or sea lizards. Only the sea crocodiles were close rela tives of the dinosaurs.
The marine reptiles of the Mesozoic did not drive the fishes out of the seas. Fishes still abounded, as they had for many millions of years, and some were
very large. One measured over 30 feet. Sharks were common. Many of the fishes made good prey for the sea reptiles.
The name ichthyosaur means "fish liz ard." The first ichthyosaur bones that were found were thought to be fish bones. In shape, the ichthyosaurs were much more like fishes than any of the other marine reptiles. Their bodies were streamlined. They had flippers much the shape of fishes' fins. Their tail was very
42
different from the tail of any land rep tile. Like a fish's tail fin, it was an excel lent propeller. The ichthyosaurs were fast swimmers.
An ichthyosaur's mouth was full of sharp, strong teeth. A fish once caught had little chance to get away. The eyes of ichthyosaurs were enormous. Perhaps, some scientists think, these fishlike rep tiles did most of their hunting at night, when the light was dim.
There were great ichthyosaurs over 35 feet long. The average length, however, was only 10 feet or so. Fossils of ichthyo saurs have been found in many different places. They were successful inhabitants of seas all over the world. These reptiles were probably better fitted for living in the sea than any others in earth history. They were bound strictly to the water, for their flippers could not possibly have served as legs. The ichthyosaurs could not even crawl up onto land to lay their
