00:16Once, there was a time when huge beasts, such as these great dinosaurs, roamed the earth.
00:26For almost 150 million years, they were part of the world's life.
00:34We know they were here because their bones or fossils have been found on nearly every
00:38continent including North America, a great many of them in the United States.
00:48If you draw a line to represent time from the present, back 450 million years into the past,
00:55you can see that the fishes began here.
01:00Then came the amphibians, the reptiles, the mammals, and the birds.
01:17Fishes, amphibians, reptiles, birds, and mammals.
01:27The dinosaurs began about here 225 million years ago.
01:32The last of them were gone about 70 million years before man appeared.
01:37Man has lived on earth a comparatively short time, only about a million years.
01:44Some dinosaurs, such as the brontosaurus, were enormous.
01:48They grew to be as long as 70 feet, the size of a house.
01:52One could weigh as much as 25 tons, the weight of 12 automobiles.
02:02Not all dinosaurs were big, however.
02:07Here is one, Coelophysis, which was only about eight feet long.
02:13He was a meat-eater, lightweight for his size, and very fast.
02:30The great brontosaurus was slow, spending much of the time in the water of warm, tropic swamps,
02:38probably going on land only to lay its eggs in the dry, sun-drenched sand of the beaches.
02:47Like most reptiles, the dinosaurs, reproduced by eggs.
02:53In the water, the brontosaurus found support for its huge body and a ready supply of its
02:58favorite food, water plants.
03:10Unlike warm-blooded mammals, the dinosaurs were not able to keep a constant body temperature.
03:15They depended upon the warmth of their surroundings to maintain body heat.
03:29Some dinosaurs had special ways of protecting themselves.
03:34The stegosaurus, a plant-eater, had an armor of bony plates that shielded him from his enemies.
03:54His spiked tail could be a dangerous weapon.
04:03Then there was Tyrannosaurus, a vicious meat-eater that grew as long as 50 feet.
04:11His huge head was mostly mouth, filled with knife-like teeth.
04:18His short forelimbs were of little use to him, and he was so slow that he probably could catch
04:24only old or sick animals for food.
04:29Triceratops belonged to a group of dinosaurs called horn-faces.
04:39He was the largest of these, and any other animal would hesitate to attack him.
04:46Another horn-face, Monoclonius, developed a single horn on his snout, much like the present-day
04:52rhinoceros.
05:00All of the horn-faces were plant-eaters, and all had beaks, like carrots.
05:13.
05:33The Trachodons, called duckbills, were from head to tail as long as a large truck and
05:37trailer.
05:38They, too, were plant-eaters.
06:05The tops of their heads, however, differed greatly in shape, making several varieties
06:10of duckbills.
06:15The flying reptiles seen in the background are pteranodons.
06:19They lived at the same time as the duckbills but are not members of the dinosaur family.
06:34Of course, it's important.
06:35Bye.
06:35Bye.
06:49Bye now.
06:51Bye.
06:54Let's go.
07:44As centuries went by, the lands and climate in which the dinosaurs lived changed.
07:50Those able to adapt to new conditions continued to thrive.
07:59Here is the Ankylosaurus, one of the last dinosaur survivors.
08:06The horned lizard of today is cold-blooded like the dinosaurs.
08:25This South American iguana is also a cold-blooded reptile.
08:33The last of the dinosaurs were gone about 70 million years ago.
08:38How do we know as much about them as we do, considering the fact that they were gone long
08:43before man appeared?
08:46There is no agreement as to why they died out.
08:49One belief is that they died because the climate changed, another that possibly the food supply
08:56became inadequate, and still another that mammals ate the dinosaur eggs.
09:00We just don't know.
09:05Our world today is still changing.
09:07Why would it be helpful for us to know why some animals succeed in surviving as the world
09:12changes and others, such as the dinosaurs, do not?
09:44Why would it be helpful for us to know why some animals succeed in surviving as the world?
09:44Why would it be helpful for us to know why some animals succeed in surviving as the world?
