Compsognathus (kahmp-SAHG-nuh-thuhs)
About 150 million years ago,at the same time creatures like 34 foot-long Allosaurus were stalking the swamps in search of a 70 -foot- long Apotosaurus, a tiny reptile not bigger than a chicken was also scurrying about among the ginkgoes and cycads. It had a 3-inch long head on a long, slender neck, and its tail was longer than its head, neck, and body all together. It ran swiftly on its two back legs. This little animal was a dinosaur--one of the smallest of all the dinosaurs. Its name is Compsognathus, which means "graceful jaw."
Apatosaurus (uh-PAT-uh-SAW-ruhs)
Giant long-necked, long-tailed creatures such as this were the biggest of all the dinosaurs that have ever lumbered upon the land. They were plant eaters that walked on four legs, and we call them the sauropod dinosaurs.One of the best known of these sauropods is the dinosaur that many people called Brontosaurus. But that isn't its right name. Scientists call it Apatosaurus which means "unreal lizard" or "untrue lizard."
Perhaps Apotosaurus got its name because the scientist who found it couldn't believe it was real! from the end of its lengthy tail to the tip of its nose, apatosaurus was about 70 feet long and about 15 feet high at the shoulder and weighed as much as five full-grown elephants. It was a living, moving mountain of bone, flesh and muscle!
Stegosaurus (STEG-uh-SAW-ruhs)
All the dinosaurs were strange looking creatures. But surely the strangest of all was Stegosaurus, a dinosaur that lived in North America about 150 million years ago.For one thing, when you look at a picture of Stegosaurus or at its fossil skeleton, you wonder how such a big animal could have such a tiny head. Stegosaurus's body was about 20 feet long and weighed about 2 tons, but its narrow, birdlike head was only 16 inches long. The brain in that head weighed only about 2 ounces and was no bigger than a walnut. For another thing, Stegosaurus's back legs were more than twice as long as its front ones. Thus, while its nose was nearly touching the ground, its rear end was nearly 8 feet in the air. No other dinosaur was quite as oddly shaped. Lastly, and perhaps the strangest feature of all, along Stegosaurus's back and down most of its tail marched a row of bony plates that looked like the spades in a deck of playing cards. The plates on Stegosaurus's neck were small, but they got bigger the farther back they went, with those at the hips being 2 feet high. Each plate was about 2 inches thick and covered with tough horny skin.
Stegosaurus gets its name from these strange bony plates. Professor O.C. Marsh, who first discovered fossils of Stegosaurus, felt that the bony plates looked like roof shingles. So he gave the animal its name, which means, "roofed lizard."
Tyrannosaurus (teh-RAN-uh-SAW-ruhs)
Tyrannosaurus "king tyrant lizard" walked on it two strong heavy back legs, and when standing upright, was about 20 feet high. A tall man would have reached only to its knee. Its powerful body was nearly 40 feet long and weighed 7 1/2 tons. The claws on Tyrannosaurus's three toed feet were abut 8 inches long. Its huge head was nearly 5 feet long and its jaws were filled with inch thick teeth, pointed like daggers and saw-toothed like the cutting edge of a steak knife.
The tyrant reptile king lived about 70 million years ago in the western part of North America. It was the biggest part of all the flesh eating dinosaurs in the world but it was not the only one of its time. It had a sort of cousin called Albertosaurus (because its fossil bones were found in Alberta, Canada) that lived at about the same time and in the same part of the country as Tyrannosaurus . Albertosaurus looked much like Tyrannosaurus but was considerably smaller. And there was a very strange flesh-eating dinosaur named Spinosaurus that lived where Egypt is today. This creature ,too looked much like Tyrannosaurus, but on its back was a huge fin as much as 6 feet high, shaped like the fin on the back of a sailfish. Most scientists think this fin may have helped keep Spinosaurus from getting too hot or too cool.
Ankylosaurus (ANG-kih-loh-SAW-ruhs)
Ankylosaurus was a dinosaur that wore armor and carried a club! his name means "stiff lizard," but a better name for this creature might have been "bumpy lizard"! for Ankylosaurus's head, neck, back, and tail were covered with a bumpy armor of thick, rock-hard ovals of bone embedded in tough skin. This armor was not stiff and solid like the shell of a turtle; it was flexible, like the bony shell of a modern armadillo.However, Ankylosaurus didn't depend on its armor alone for protection. It could fight, and fight well. Its teeth were dull and weak, and it had no sharp claws, but its tail was thick and powerful and tipped with a huge, round mass of bone--nothing less than a massive and deadly club! Ankylosaurus's head was broad and blunt and looked much like the head of a horned lizard of today. This resemblance was increased by shelves of bone that stuck out of its head. These shelves helped protect Ankylosaurus's eyes. even it eyelids had bony shields embedded in them.
Triceratops (try-SERR-uh-thps)
Seventy million years ago, herds of four-footed dinosaurs browsed on the spiky fronds of palm trees and cycads. They were fairly large dinosaurs, up to about 30 feet long and 10 feet high--much longer than a big elephant but not quite as tall. Their tails were short and heavy, and their legs were thick, with broad, flat feet to support the weight of their bodies. Their toes were clawed--three claws on the toes of their front feet and four on the back-- but the claws were small and blunt, like little hooves.These dinosaurs had enormous heads that were nearly a third as long as their whole bodies. And out of the backs of their heads grew big shields of bone that spread out to cover their necks and shoulders. Their jaws were curved like parrot beaks and they browsed by cocking their heads to one side and snipping off leaves and fronds with their beaked mouths, as neatly as you might snip flowers stems with a scissors.
But the most striking thing about these bulky reptiles were the horns that stuck up from their heads-- a sharp, 3 foot long horn above each eye and a short thick horn that poked up from the nose. It is from these horns that the dinosaur gets the name Triceratops.which means "three horned face."
Dinosaur Mysteries
> How do scientists decide what dinosaurs looked and acted like? After all, these creatures lived during the Mesozoic (Mez-uh-ZO-ik) Era, between 225 and 65 million years ago! We don't have any living dinosaurs to study. Scientists who study the remains of these ancient animals are called paleontologists (PAY-lee-on-TULL-uh-lists.) Better named for them might be detectives! Putting together a picture of the dinosaur world is like putting together a giant jigsaw puzzle--with most of the pieces missing. Rebuilding The Dinosaurs.
Fossils--The Building blocks
The scientist's picture of a dinosaur starts with the bones left behind when the creature died. Over millions of years these bones become covered in rock. The bones themselves turn into rock as the real bone disappears. But the rock fossil left behind tells us exactly what the bone was like.
Whole dinosaur skeletons are rarely found. Usually, the bones are broken up and spread over a wide area. Sometimes, the bones of different animals are mixed together. Many pieces may be missing. Scientists must carefully remove these bone fossils from the rock they are trapped in. The pieces are studied and put together to make whole dinosaur skeletons. This process can take many years.
A skeleton can tell us a lot about the animal it belongs to. We can guess how tall and long the creature was. We can tell if it walked on two legs or four. Scientists can also make good guesses about how much an animal weighed.
Apart from showing what dinosaurs looked like, the bones can tell us a little about how they lived. Some dinosaurs had sharp teeth and claws. This tells us they ate meat. Others had rows and rows of blunt teeth. These were good for chewing leaves and branches. The bones can also tell us about how some dinosaurs protected themselves. Dinosaurs that had plates horns, or spikes would have been more difficult to attack.
Working From The Inside Out
Paleontologists have to know a lot about today's living animals. Knowing how modern animals are built helps these scientists put the dinosaur bones together. Sometimes, they are lucky enough to work with bones that are in very good condition. These bones might have marks that show just where the muscles were attached. Scientists can then build the dinosaur models layer by layer.
One thing we don't know much about is dinosaur skin. The soft parts of animals usually do not survive as fossils. So we often must guess what the outsides of dinosaurs were really like.
Were Dinosaurs Warm-Blooded Or Cold-Blooded?
Like all human beings, you have warm blood in your veins. Having warm blood helps us to do many things that cold-blooded animals cannot do. Since dinosaurs were first discovered, they have been considered cold-blooded animals. But now some scientists say they must have been warm-blooded. What difference would this make? Why do scientists think it is important to know so much about dinosaur blood?
Endotherms and Ectotherms
Warm-blooded animals can produce their own body heat. They do this with the energy they get from eating food. Animals who can control their own body temperatures are called endotherms. Birds are endotherms. So are mammals such as humans, horses and whales.
Cold-blooded animals have to depend on heat from their surroundings to keep their bodies warm. If the weather is cool, these animals become inactive. If the weather stays cool, they may die. Cold blooded animals also have to protect themselves from too much heat. On very hot days, they have to take to the shade. Animals that depend on the sun for their body heat are called ectotherms.
These include fish, lizards and other reptiles, and amphibians like frogs and newts.
Changing The Way We Think About Dinosaurs
If dinosaurs were warm-blooded we would have to change much of our thinking about them. Warm-blooded animals can survive in places that are too cold for ectotherms. Endotherms can keep up a much faster pace of life. They can travel farther than cold blooded animals too. Endotherms also have to eat more than ectotherms. so warm-blooded dinosaurs would have needed more food. If some dinosaurs were warm-blooded, they may have been a lot smarter than we first thought they were. All of this means we may have to throw out some of our ideas about why dinosaurs disappeared.
The Speedy Dinosaur
Deinonychus (Dine-ON-ik-us)
The discovery of a speedy little dinosaur convinced some scientists that certain dinosaurs were warm blooded. The bones of this dinosaur were found in the late 1960s. It was given the name Deinonychus. This means "terrible claw." The animal got its name from a hooked claw on each of its hind legs. The claw seemed to be made for slashing and tearing at other animals.
Scientists put together Deinonychus's small size and sharp claws. They decided this must have been a very fast hunter. They thought only a warm-blooded animal would have had the energy to move that quickly.
Today's Dinosaurs--On The Wing
Look up in the sky or at the high branches of a tree. Could the little feathered creatures there be modern dinosaurs? Scientists once thought that the dinosaur family came to a dead end sixty-five-million years ago. But now it seems that at least some dinosaurs have lived on--as birds!
Ancient Wing
In 1861, the bones of a small, light creature were discovered in a German mine. In many ways, it was like the small, meat-eating dinosaurs such as Coelophysis (See-low-FISE-iss)or Velociraptor (Veh-loss-ih-RAP-tor). But the rock around the fossils was covered with the marks of ancient wing,tail, and body feathers. And so the new creature was given the name Archaeopteryx (Ar-kee-OP-ter-ix). It means "ancient wing."
Archaeopteryx was the first possible link between dinosaurs and birds. Like the dinosaurs, it had a toothy jaw, long tail and claws on its feet. It also had claws on it wings. Like the birds, Archaeopteryx had light bones and feathers. But its wings probably did not make it a good flyer. Archaeopteryx's breast muscles were not strong enough to flap the wings very hard.
Scientists formed the theory that Archaeopteryx was the ancestor of modern birds. Since then, many people have thought of "ancient wing" as the missing link between birds and dinosaurs.
When Did the Dinosaurs Disappear?
Whatever killed off the dinosaurs seems to have happened suddenly, about sixty-five million years ago. That is when the last fossils date from. At least that is what scientists agreed on--until recently. A group of scientists have a new theory about the end of the dinosaurs. They say these animals did not all die at the same time. Instead, the Age of Dinosaurs ended slowly over millions of years.
Fewer and Fewer Dinosaurs
We usually think of the dinosaurs being wiped out while they were at the peak of their development. But scientists studying bones in Montana think dinosaurs were dying off before sixty-five million years ago. These scientists say that in the last million years of the dinosaur age, the number of dinosaur types probably dropped greatly. They think the dinosaurs were dying off because of a change in the weather. Plant fossils from the time show the climate was getting cooler.
Other scientists disagree with this theory. They say that the bones studied in Montana were too badly broken to be solid evidence. They say we can't be sure about the variety of dinosaurs these bones and teeth were from.
Dinosaur Survivors
Still other scientists say they have found dinosaur fossils that are less than sixty-five million years old. Were these from survivors who lived on after the other dinosaurs became extinct? These "young" bones have been found in China and Montana. Some are from almost a million years after the dinosaurs were supposed to have disappeared.
Not everyone is convinced. Remember that the age of fossils is mostly determined from the layer of the earth that they are found in. Some say that the "young" fossils are in fact, old fossils. They might somehow have been moved to a different layer of the earth. The earth around them might have worn away long ago, leaving them above ground. Water might have moved them to a newer part of the earth's surface. Anyone who later discovered the fossils would think the fossils had died at that time in the earth'a history.
So did the dinosarus die all together in one mysterious disaster? Or did they die over many years, as the earth's climate cooled? What ever caused their death did not kill off all other animals. Among the survivors were the early mammals. With their biggest competitors wiped out, these small, warm-blooded creatures have thrived ever since.~~~~~~~~~~~~~~~~ SOURCE INFORMATION
DINOSAURS & OTHER PREHISTORIC ANIMALS
Written by Tom McGowen
Illustrated by Rod Ruth--
DINOSAUR MYSTERIES
Written by Mary O'Neill
Illustrated & Designed by John Bindon
Get your own Free Homepage
