Dinosaurs - the Terrible Lizards

[Music] encyclopedia britannica educational corporation presents from life on earth dinosaurs the terrible lizards [Music] so [Music] a moment from prehistoric time a battle to the death between two great dinosaurs a battle that took place more than 130 million years ago they were the greatest land animals that ever lived but why did they suddenly vanish after ruling the earth for 150 million years how small were they how large did they grow are there any alive today these are just a few of the questions surrounding these fantastic animals join us as we unravel some of the mysteries of these incredible creatures from our past these terrible lizards [Music] imagine a time when fiery volcanoes erupted into a prehistoric sky the earth's climate was wetter and warmer than it is today much of north america was still under water this was our world 225 million years ago at the beginning of the mesozoic era the age of reptiles reptiles owned the skies the land and the sea and the greatest of all the reptiles were the dinosaurs many were small a few were giants such as the 12-ton apatosaurus some of these strange beasts were protected by massive plates of bony armor dozens of species had crested oddly shaped heads the duck bills and there was the terrifying tyrannosaurus rex the dinosaurs dominated the earth for 150 million years and then suddenly about 70 million years ago something went terribly wrong almost overnight in geologic terms the dinosaurs died one by one large and small they vanished a question that scientists are now trying to answer is what animals are alive today that could be relatives or even descendants of the terrible lizards we're often asked if there are any living dinosaurs the answer is very definite no we know all of the large animals on the surface of the earth and we know practically all of the large animals in the ocean today there are no living dinosaurs and their only living relatives are the crocodiles [Music] but are they some evidence suggests there may be many more from further back we might even view the birds as distant relatives of the dinosaurs and as much as birds and dinosaurs had a common ancestry towards the beginning of the age of reptiles one day scientists may prove that every feathered animal alive is descended from some of the smaller types of dinosaurs birds are one class of the vertebrate branch of life on earth today those animals that have a spinal column or backbone supporting their skeletons some vertebrates adapted to life in the sky others to life in the sea there are thousands of species of fishes vertebrates such as salamanders and frogs are amphibians living both on land and in the water a highly specialized class is the mammals warm-blooded animals that breastfeed their young finally there are the reptiles today this class contains about 6 000 species of lizards snakes crocodiles and turtles they are all that remain of the incredible variety of reptilian life that once existed that once ruled the earth the importance of the reptiles is that they were the dominant animals they were the uh animals occupying the swamps the highlands and the air and the sea [Music] the oceans were filled with a large number of reptiles among them the closest thing to a sea serpent that ever lived the mosasaur this was a gigantic sea-going lizard that ranged up to 12 meters in length to adapt to their watery environment they evolved flippers and a swimming tail fin instead of feet flying reptiles filled the skies the pterodactyls [Music] this is a display in preparation of what is probably uh currently the most famous fossil bone on record the object here is a replica of the upper arm bone from the wing of a flying reptile found in west texas and after careful study it is clear that this bone represents the largest flying creature ever found the wingspan of this flying monster would have been about fifteen and one half meters pterodactyls had a leathery skin instead of feathers this tough skin stretched between the neck wingtips and legs providing a large surface that enabled them to sail and glide across the land we believe they were scavengers their long necks let them reach deep into the bodies of dead dinosaurs to feed the way vultures do today flying reptiles ruled the air marine reptiles ruled the sea but on the land the greatest of all the reptiles the dinosaur was king [Music] dinosaurs came in all shapes and sizes the smallest ones were probably about the bulk of bulk of a turkey this one here an armored dinosaur known as ankylosaurus is uh about intermediate size and then they range all the way up to these gigantic amphibious dinosaurs such as the diplodocus diplodocus was by no means the biggest of the dinosaurs another type known as brachiosaurus was at least twice the size of the diplodocus duck bills were the most numerous of all dinosaurs this was a rather small one others grew to 15 meters in length [Music] these plant eaters or herbivores had as many as two thousand teeth in their jaws at one time a hundred of these might actually be in use the rest would be pushing outward to replace teeth that had worn away the duckbill dinosaurs lived and traveled in herds you might call them the antelopes of the age of reptiles they provided much of the menu for the carnivores such as tyrannosaurus rex as tall as a two-story building he could kill almost anything that crossed his path with massive jaws filled with razor-sharp teeth tyrannosaurus rex was a terrifying sight [Music] some dinosaurs develop protective armor to guard themselves from beasts like tyrannosaurus rex the most spectacular of these was triceratops a 10-ton monster the huge shield covered its neck and throat while its long vicious horns could tear apart the body of an attacker [Music] this armor-plated dinosaur is stegosaurus triangular plates of bone protected his spine and to defend himself he had a clump of long spikes on the end of his tail he could swing these spikes like a club to rip open the belly of an enemy stegosaurus had one of the smallest brains of all the dinosaurs its body was bigger than an elephant its brain the size of a walnut all dinosaurs had extremely small brains because of this they are often thought of as unintelligent this is the brain case of a diplodocus dinosaur which fits in this skull in this position this opening here corresponds to this opening this edge corresponds to that edge and so you can get from that a fairly uh graphic idea of just how small a space was occupied by the brain of the dinosaur when one comes to discuss intelligence a matter of definition is necessarily involved what constitutes intelligence if survivability of a group of organisms has anything to do with intelligence then i think that there's some food for thought in the fact that the dinosaurs with their gigantic bodies and their tiny brains survived on earth for a period of 150 million years or so whereas man with his tiny body and gigantic brain has been on earth only 2 million years or so and according to some may be close to the end of his existence here [Music] the dinosaurs are dead yet in our imaginations in books and in films they are very much alive they are strange wonderful and mysterious animals [Music] so [Music] in some ways we know little about dinosaurs one reason is that finding and restoring the bones of these monsters is a difficult costly task this is the skeleton of a sauropod dinosaur one of the giant amphibious dinosaurs that lived about 120 million years ago this skeleton belongs to a species technically called diplodocus but perhaps more popularly known as a brontosaurus the name brontosaurus means thunder lizard because the people who first described brontosaurus suggested that it was so big that when it walked the ground must have thundered it's a very costly business nowadays to articulate a dinosaur which explains probably why so few large specimens such as this diplodocus at the houston museum have been assembled since world war ii starting from scratch a skeleton of this type today would cost a hundred thousand dollars or more from the time it was discovered until it was finally installed for public view in the museum [Music] the search for dinosaur bones begins in a place like this the mountains of western colorado once this was a broad low-lying plain covered with tropical vegetation today it has been raised 2300 meters above sea level as the earth's crust was pushed up erosion weathered away the rock exposing long buried fossils this quarry has provided scientists with many dramatic fossil discoveries i found one of the world's largest land animals at the dinosaur that stood between 50 and 60 feet tall and probably weighed about 80 tons [Music] we never dig until we see dinosaur bone coming out of the ground otherwise we might dig forever and never find a bone but to find a dinosaur bone or skeleton one must walk a long ways climb a lot of sweaty mountains and uh go thirsty and be subjected to gnats and heat and that sort of thing but when you find something like this it may be something that's never been seen before so it's an exciting pursuit this is the vertebrae right up next to the skull the first one we found of this kind it's called the atlas axis for some members of jim jensen's crew the quarry is also a classroom the excitement of a dinosaur hunt brought rod and mike sheets to this site the two boys found their first fossils when they were on a family picnic they were soon caught up in the world of dinosaurs i first started working this great three years ago and i worked in a certain area with my little brother along with dr jensen and his son my last project i worked on in school was on dinosaurs in general but right now i'm working in the query at the same time i'm working on uh pterosaurs pterodactyls pteranodons and thinking of two things at the same time off workout imagine a pterosaur flying through the air and yet also thinking about wanting to do tomorrow in the quarry once a dinosaur bone is found and uncovered it is hardened with shellac then it is covered with tissue paper so plaster won't stick to it a coat of plaster of paris and burlap is applied forming a protective jacket around the bone the crew then digs down into the ground around it deeply enough so that it can be turned over digging these bones out of the ground is a slow process after the bone is turned over the same procedure is followed the bone is shellacked tissue paper is applied then the plaster jacket now a stick or tree limb will be plastered in alongside the bone so that the entire block can be picked up by a chain or cable without damaging the specimens inside the plaster blocks are then hauled to a museum laboratory using these methods in the first year jim jensen and his crew took 18 tons of rock and bone out of the colorado quarry when you see this ball oh this block was probably always about two or three hundred pounds in a laboratory like this one in austin texas the bones are prepared for study the first step is to cut away the plaster jacket the bones are always surrounded by a rock matrix this was originally mud or sand that covered the dinosaur when it died it has become solid rock through countless centuries of pressure from layers of earth that built up over it when the jacket has been removed the matrix must be carefully chipped away it is a slow process time seems to take on a different meaning for those scientists who work in the world of dinosaurs perhaps it is understandable these bones have been buried in the earth for many millions of years actually the way this material was coming off of here it won't take too long to work this bone out probably a month or so this is a reconstructed rib that will be installed on the diplodocus skeleton fossil skeletons are never found complete they're always missing bones missing parts parts that are crushed or broken to the point where they can't be used and in instances of that type we use a best estimate of what the missing part may have looked like and model it out of plastic or plaster or some such material enough fragments of this rib were found so that the original bone could be mounted on the reconstructed skeleton a hole is drilled through each of the pieces so that the supporting steel framework will be hidden from view hey all right it's perfect good fit real good fit now we have about 16 more like it we have to make the rest of the objects which you see here uh are bones that have been largely uh reconstructed completed and are ready to assemble on the steel framework every dinosaur skeleton presents its own special set of problems by the time this diplodocus was completely ready for public display in houston texas many years had passed that time included all the scientists work discovering the specimen in the field collecting it and preparing it in the laboratory mending broken bones reconstructing missing bones building the huge steel framework and finally assembling the skeleton but when the last bone was put into place and the skeleton was complete these men certainly felt a strong sense of accomplishment they had brought back to life one of the greatest animals that ever walked the face of the earth we have much to learn about the age of reptiles but one thing we know for certain about 70 million years ago the flying reptiles the marine reptiles and the dinosaurs banished from the earth and there has never been anything quite like them since still the biggest question of all surrounding the dinosaurs is why did they suddenly become extinct organisms must be able to adapt to changing environmental conditions the dinosaurs became extinct because some conditions in their environment changed and they were unable to adapt to the new conditions we may not know what these changes were but this is the ultimate explanation of extinction of all organisms when the dinosaurs died a spectacular chapter in the history of life on earth came to an end man is working to reconstruct that chapter word for word to find out how the dinosaurs lived where they lived and why they disappeared someday we may unravel the mystery of why the dinosaurs became extinct if we do we may use that knowledge to prevent the extinction of another of nature's great experiments man [Music] you