dinosaurs
TRANSCRIPT
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 The End of the Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
A GOLDEN EXP··LORING EARTH BOOK
DINOSAURS Dinosaurs-those "terrible lizards" of the past-
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 of Western Publishing Company, Inc.
/
When such a l ife-size restoration is electronically animated, the creature seems· a lmost as rea l as the animals we see at the zoo.
Out of the Past
No one has ever seen a dinosaur, and no 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 powerful meat eaters.
In their time, the dinosaurs were numerous 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 dinosaurs and dinosaurs with so many teeth that you could count them by the hundred. Hooves, claws, spikes, topknots, and rufflike 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 restoration of Stegosaurus, one of the socalled plated dinosaurs.
3
Since the World Began
Even as long ago as the days of dino
saurs, 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 magnifying 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
chlorophyllappeared in plant cells 2.5 bil lion 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 Paleozoic, the leading animals were all invertebrates-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.
.. .,_0 o E ., E (1)0 <�
How We Find Out
The last dinosaurs died more than 60
million years before there were any people on the earth. Of course, then, no written records have come down to us from dinosaur 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 fossils. 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 material 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
Stegosaurus
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 thecodonts, 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 became 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
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+- Living Reptiles -+
Tricenltopa
alligators and crocodiles
Thecodontsancestors of the dinosaurs
Cynognathus
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
North America ,_
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Europe and Asia
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South America
Africa Madagascar
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Antarctica
do. 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
North America
Europe and Asia
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South America
Africa
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-equal�-----------------South Africa America
Antarctica
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 together 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 America 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.
1 3
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� 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 dragonfly 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 enormous 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 lizardhip dinosaur group (Saurischians), represented here by Gorgosaurus and Camarasaurus, 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, dinosaurs 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 mil l ion years, these four groups otrepti les 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
All igator
Pterosaurs (flying reptiles)
Lizard-Hip Dinosaurs
Camarasaurus
Bird-Hip Dinosaurs
•
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 giant whales
live 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
17
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 of 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 happens 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.
19
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
II
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 dino
saurs 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 cousins 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 mostly 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
Ovi raptor
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.
23
Allosaurus
Giant Meat Eaters
The living things of every natural re
gion 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 eaters. 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
25
Skul l 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 agape 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 jaws 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 pursuit 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.
27
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, it
walked 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
Scel idosaurus
.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 instance, 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.
29
An kylosaurus
Ankylosaurus
Giant Tortoise
Armored Di nosaurs
The armored dinosaurs filled the same
niche 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 covered 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 protection. 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 Stegosaurus, 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.
3 1
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 several 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
3 3
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
Trachodon
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
3 5
Protoceratops
Horned Dinosaurs
Protoceratops was, in a way, the be
ginning 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 dinosaur 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 .
Styracosaurus
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.
F lyi 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 Jurassic, 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.
4 1
Ichthyosaur
Marine Repti les
As you know, the dinosaurs were land
animals. 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
•
eggs, as sea turtles do today. Their young
were born alive, in the sea.
Probably these fish-lizards swam in
schools, as dolphins do now. Since they
could not breathe underwater, they had
to come to the surface often for air, just
as dolphins have to.
It is easy to recognize Archelon as a
turtle. So far as anyone knows, it was the
largest one that ever lived. It grew to a
length of 12 feet. The skull alone was a
yard long. Archelon had enormous pad
dles that pushed it rapidly through the
water. The big sea turtle was well ar
mored, as it needed to be, as protection
against sharks and some of the fierce
meat-eating reptiles that shared the seas
with it.
Today's crocodiles are found in
swamps, in streams that empty into the sea, or in shallow waters along seashores.
Often they climb out of the water to lie
on the banks or shores. The crocodiles of
the Age of Reptiles, too, were mostly
Archei on
shallow-water prowlers, but some took to living in the ocean. These were the sea crocodiles. The legs of these crocodiles
had become paddles and their crocodile
tail a fishlike one, much like the tail of
an ichthyosaur. The sea crocodiles were
abundant for a while, then disappeared.
Trinacromerum, the 10-foot-long sea
reptile pictured with Archelon, was a
plesiosaur. The name plesiosaur means
"neighbor of lizards." A German name
for plesiosaur means "swan-necked
dragon." Swan-necked dragon hardly
seems a good name for Trinacromerum, with its long crocodilelike snout and
rather short, thick neck. But the name is
a good one for the kind of plesiosaur it
was meant for. This plesiosaur had a
long, slender neck which, when held up
out of the water as the plesiosaur swam
near the surface, would have looked
swanlike.
The body of even a long-necked ple
siosaur was not slender. It was much the
Trinacromerum
Elasmosaurus
44
shape of a turtle's. In fact, it has been
said of the long-necked plesiosaurs that
they looked as if they had started out to
be turtles and then changed their minds
and decided to be snakes.
Elasmosaurus was the long-necked
plesiosaur giant. Here are the measure
ments of one 42-foot fossil specimen :
head, 2 feet; neck, 23 feet; body, 9 feet ;
tail, 8 feet. Like other plesiosaurs, Elas
mosaurus often flopped up onto land. It
had to lay its eggs on land.
Portheus-a large fish
There were plesiosaurs in the seas all during the days of the dinosaurs. Fossils
of them have been found in many
different places, but they are not as
numerous as fossils of ichthyosaurs.
Tylosaurus was a mosasaur. The mosa
saurs lived in the days of Tyrannosaurus.
Many fossils of them have been found
with fossils of that "neighbor of lizards,"
Elasmosaurus.
The mosasaurs swam by wriggling
from side to side, much as snakes do.
They had paddles, but these served chiefly as rudders. The sea lizards were
fast swimmers. They and the sharks were
the chief enemies of the ichthyosaurs .
Of all the reptiles of the Mesozoic that
went to sea, the only ones with close rei- .
atives among living reptiles are the sea
turtles, the sea lizards, and the sea croco
diles. Even though they dominated the
sea for many millions of years, the ich
thyosaurs and the plesiosaurs went the way of flying reptiles and dinosaurs.
Archaeopteryx
Early B i rds and Mammals
The earliest bird scientists know about
is Archaeopteryx. Its name means "an
cient wing." This early bird appeared
some 20 million years later than the first
flying reptiles, in the time of Brontosau
rus and Diplodocus.
The scientists who first found fossil
bones of Archaeopteryx would have
called the creature a dinosaur, had they
not found imprints of feathers near the
bones. Its skeleton was much like that of
a small dinosaur. The bones were all sol
id, whereas many of the bones of today's
birds are hollow.
46
This ancient cousin of the dinosaurs
was about the size of a pigeon but very
different from a pigeon in many ways.
Instead of a toothless bill, it had a rather
sharp beak and many teeth. On its wings
it had claws. Probably these claws helped
the creature to climb about in the trees
it lived in. The bony part of the tail of a bird of
today is very short, with tail feathers
fanning out from it. The tail of Ar
chaeopteryx was long and made up of
many bones. The feathers were arranged
along it in pairs, one to each side.
Hesperornis
Its teeth make scientists think that
Archaeopteryx was a meat eater. Perhaps
it ate dead fish washed up on shore, just
as sea gulls often do today. Archaeopteryx is pictured as gray,
brick red, and white. Of course, no one knows the bird's true colors. The fossils
of the feathers give no clue. Although we think of birds as flying
creatures, there are some birds today
that cannot fly. Among them are the os
trich, the penguin, and the kiwi. In the
Age of Reptiles, there were flightless
birds, too. One of them is Hesperornis.
Its name means "western bird." Fossils
of it were found in western states, along
with those of plesiosaurs and other ani
mals of the sea.
The earliest mammals preceded even
the earliest birds. They appeared late in
that first period of the Age of Reptiles,
the Triassic, in which the dinosaurs also
appeared. All through the long reign of
the dinosaurs, there were mammals.
Probably dinosaur eggs furnished many
a meal for those early mammals of the
Mesozoic. With their sharp teeth, they
could easily break through the· shell of a
dinosaur egg.
The early mammals were all small,
most of them no bigger than the mice
and shrews we have now. You would
have thought, if you could have visited
the earth in the days of dinosaurs, that
mammals had no chance at all of ever
getting anywhere.
Early mammals eating d inosaur eggs
This early bird that could not fly had
only traces of wings. Strangely enough,
though it had powerful legs, it could not
walk, either. Its legs were not fastened to
its body in a way suitable for walking.
Almost certainly, it was never far from
water. But the big web-footed bird-it was nearly 4 feet long-was a strong, fast swimmer and an excellent diver. In its
long beak, it had sharp teeth that helped it to catch fish and other water animals and to hang on to them.
The mammals, however, lived on-to
become the earth's leading animals. The
birds, too, lived on and are with us to
day. The fact that both birds and mam
mals are warm-blooded is certainly an
important factor in their take-over of the
earth. Warm-blooded animals, with their
covering of fur or feathers, are able to stand both heat and cold better than
cold-blooded animals. The fact that the
birds and mammals have better brains is
important, too.
47
The End of the Line
The disappearance of all the dinosaurs
some 65 million years ago marked the
end of the Age of Reptiles. Along with
them had gone also the flying reptiles
and the great Mesozoic reptiles which
lived in the sea. Many explanations for the end of the
dinosaurs-no one knows whether any
are right-have been suggested. Here are
some of them:
• Great changes took place in the earth. Mountains were pushed up. Swampy land
became desert. With sparser and less
flourishing plants to eat, the plant-eating
dinosaurs became fewer. With fewer
plant eaters, the shortage of food was
such a problem for the meat eaters that
they, too, died. • Vast stretches of what had been di
nosaur country became much colder.
The cold-blooded dinosaurs had no way
of protecting themselves from the cold.
They were too big to burrow under
ground and hibernate, as many small
48
reptiles of cold regions do today, and
they had no easy way of going to
warmer climates for the winter, as many
birds do.
• With egg-eating dinosaurs about, and with growing numbers of small mam
mals to feed on dinosaur eggs, fewer and
fewer dinosaurs were hatched.
• Cosmic rays from the explosion of
some star far out in space brought about
the end of the dinosaurs. Even a change
in the earth's magnetism-at which time a magnetic field would not have been
protecting the earth from the cosmic rays
constantly bombarding it from outer
space-could be to blame.
The puzzle is made more puzzling by the fact that some of the other reptiles,
also of ancient ancestry, among them the turtles and little tuatara of New Zea
land, somehow survived. Whatever the
answer is, not a creature alive today is a
descendant of those that once ruled the
land-the dinosaurs.
