*According to “Encyclopedia Britannica”:
Dinosaur, a term (ph) popularly used for the members of a great series of reptiles that were the dominant land animals during most of the Mesozoic Era (from 225,000,000 to 65,000,000 years ago), the age of reptiles, but became extinct at its close.
*According to “Webster’s New Collegiate Dictionary”:
“Dinosaur, any of a group (Dinosaurian) of extinct terrestrial carnivorous or herbivorous reptiles.”
*According to “Microsoft’s Encarta Encyclopedia”:
“A dinosaur one of a group of extinct reptiles that lived from about 230 million to about 65 million years ago…… dinosaurs [are distinguished] from other prehistoric reptiles by their upright rather than sprawling legs and by the presence of three or more vertebrae supporting the pelvis, or hipbone…… Dinosaur bones occur in sediments that were deposited during the Mesozoic Era, the so-called era of middle animals, also known as the age of reptiles. This era is divided into three periods: the Triassic (dating from 245 million to 208 million years ago), the Jurassic (208 million to 144 million years ago), and the Cretaceous (144 million to 65 million years ago)”.
So far, the only problem that whe have is the beginning of the Triassic Age (either 245 million years ago or 225 million years ago). Considering that the earth is 5.5 billion years old, this discrepancy is less than half of one percent, Minor.
*According to these definitions*
- A dinosaur was a reptile. There were mammals, fish, birds and other animals during the Mesozoic Era which also left fossils. These fossils will not be included.
- A dinosaur was terrestrial. That is, was a land animal. A dinosaur did not inhabit the oceans or the seas. Nor did it fly. There were marine reptiles and flying reptiles that also lived during the Mesozoic Era, along with the dinosaurs; but they were not dinosaurs.
- A dinosaur lived during the Mesozoic Era. A Dimetrodon (a carnivore) or an Edaphosaurus (an herbivore) are two sail-backed Permian reptiles. The Permian Age lasted from 286 million years ago until 245 million years ago; before the Mesozoic Era. These two reptiles existed before the dinosaurs; they are not dinosaurs as is often depicted. Animals that were ancestral to the dinosaurs will not be included.
- A dinosaur had upright rather than sprawling legs, which eliminates many of the other amphibious reptiles that lived with the dinosaurs.
I know these definitions may be simplistic, but to maintain a thematic collection of Dinosaurs on Stamps, I have had to define exactly what a dinosaur is. If I were indiscriminately include everything prehistoric in my topical stamp collection; it would distract the viewer, and may self, from the main theme which is Dinosaurs. Even though restricted, the collection has grown quite large. It presently includes over 80 countries, and thousands of stamps issued.
THE HISTORY OF DINOSAUR DISCOVERIES
Dinosaur bones have been firing people’s imaginations for hundreds of years, People in the middle Ages found huge bones that were probably fossils of dinosaurs and large aquatic reptiles, such as plesiosaurs and mosasaurus. These may have inspired the legends of dragons and giants. The oldest record of possible fossil dinosaur bones is in a Chinese book written between 265 and 317 A.D. It mentions “dragon bones” found at wucheng, in
Since those first discoveries, scientists have been trying to complete the picture of dinosaurs and their lives. All we have left of these amazing creatures are their fossil bones. Paleontologists continue their search to find all they can; each new fossil bone reveals a little more about dinosaurs. And each new dinosaur discovered tells us not only about that dinosaur also about its place in evolution.
The study of dinosaur fossils has come a long way from the first scientific description when scientific when scientists thought a Megalosaurus thigh bone belonged to a very large man. Now, scientists can tell what type of diet an animal ate, when it lived, even sometimes how it raised its young. Paleontologists are indebted to the work of the early dinosaur hunters. Their dedication laid the groundwork for today’s research.
Early Dinosaur Discoveries:- In 1677, Robert Plot, an Oxford professor, described the bottom portion of a huge dinosaur thigh bone of Megalosaurus in The natural History of Oxford shire, though he thought it was a giant human. Almost 90 years later, this bone was illustrated in an academic paper on British natural history.
Dinosaur track ways or fossilized foot prints are more common than dinosaur bones and there are many in the
Dinosaur Discoveries in 19th Century
British scientists knew that dinosaurs were reptiles, though they considered them large, overgrown lizards. In a fossil-hunting expedition in the British countryside in 1822, Mary Ann Woodhouse Mantel found fossil teeth that showed dinosaurs were different from other reptiles. She gave them to her husband, a physician. A worker at the
Harry Govier Seeley, an amateur paleontologist and professor, made a major contribution to dinosaur classification in 1887. He concluded that there were two groups of dinosaurs: the saurischians, with a lizardlike pelvis. With a few changes, scientists still use this same classification system today.
The Great American Dinosaur Rush: - In 1855, Ferdinand Vndiveer Hayden, a surveyor for the U.S. Geological Survey, took fossil teeth and other remains that he had found along the Judith River in
Two years later, William Parker Foulke made an amazing discovery while vacationing in Haddonfield, New Jersy. John E. Hopkins had found some large vertebrae on his property two decades before. Souvenir hunters had carried off many of the bones, but Foulke and his workers found the rest of the skeleton. Leidy described the headless specimen as a new dinosaur, Hadrosaurus foulkii. It was the first dinosaur skeleton found in North America and one of the best found anywhere up to that time.
In the late 1860’s two scientists took the spotlight. Their rivalry has become legend. Othniel Charles Marsh, Nephew of multimillionaire George Peabody, was a
Edward Drinker Cope grew up a Quaker in
Cope and Marsh’s rivalry grew out of their ambition to be the greatest paleontologist. By 1866, Cope had described his first dinosaur, the meat-eating laelaps aquilunguis. Marsh had not yet described a dinosaur. He pointed out errors in Cape’s 1868 description of the aquatic reptile from
Marsh’s and Cope’s ambition to be the first to describe the largest and most spectacular fossils started the “dinosaur rush” that lasted for a decade. They hired teams of men to find new locations, to dig for dinosaurs, and to send bones to
Cope died in 1897, and Marsh in 1899. After the smoke cleared, Marsh had described more dinosaurs than Cope. Cope’s interests in paleontology were wider than Marsh’s, though, and he made the greater contribution. The techniques of prospecting, recording, excavating, and shipping large fossils are perhaps the two scientist’s greatest legacy.
Henry Fairfield Osborn had just graduated from
The size and appearance of dinosaurs impressed Osborn. He realized that they also fascinated the general public. Using his connections, he secured funding to find, prepare, and display dinosaur skeletons. By 1940, the
As the 19th century was ending, Andrew Carnegie endowed a large natural history museum in Pittsuburgh. After reading about the
Earl Douglass went to work for the
Dinosaur Discoveries in
Geologist Thomas Chesmer Weston boated along the
Charles Hazelius Strenberg’s childhood interest in fossil plants led to a job as a fossil collector for Cope. The Canadian Geological Survey hired Sternberg in 1912 to find dinosaur skeletons and send them to
Workers have found more dinosaur specimens in southern
Dinosaur Discoveries in
Louis Dollo devoted his life to preparing, mounting, and studying these skeletons, making lguanodon the best known European dinosaur. Dollo’s work inspired younger European paleontologists, who carried the study of dinosaurs forward.
One colorful character was Franz Baron Nopcsa won Felso-Szilvas, a Transylvanian nobleman. He became intrigued with dinosaurs when his sister chanced upon some bones on her property in what is now
Much of Nopcsa’s work was to describe the dinosaurs of central
Dinosaurs of Africa:- W. B. Sattler found the most interesting African dinosaurs in 1907 near
One spectacular result was the 40 feet tall skeleton of Brachiosaurus brancai which now stands in the East Berlin Natural History Museum. Assembled from the bones of several animals, it is the tallest mounted dinosaur skeleton in the world. Also found were skeletons of the spiny plated dinosaur kentrosaurus and remains of the huge plant eaters Barosaurus africanus and Dicraeosaurus. The Tendaguru finds resembled the dinosaurs discovered in the western
After World War I, the English continued the work at Tendaguru. By 1929, work at Tendaguru ceased. Recently, paleontologists have returned to the region to continue the search for dinosaurs.
In the autumn of 1912, word of a find of large dinosaur bones reached Ernst Freiherr Stromer von Reichenbach at the
In the early 1930s, Stromer wrote up three Egyptian dinosaurs: Aegyptosaurus, a giant plant eater; Gahariasaurus, a giant meat eater rivaling Tyrannosaurus; a smaller carnivore. Unfortunately, a bombing raid during World War II destroyed Strummer’s specimens, including some that had not been described.
From the late 19th century until the 1950s, French paleontologists studied the dinosaurs of
In 1936, an expedition sponsored by the Museum of Comparative Zoology of Harvard University went to the Santa Maria Formation of Rio Grade do Sul. Headed by Llewellyn lvor Price and Theodore E. White, the prospectors brought back a large collection of fossils that included the partial skeletion of Staurikosaurus pricei. It was described by Edwin Colbert in 1970. Scientists consider this the oldest known “true” dinosaur.
Price remained in
In 1958, Sohan Lall Jain, Tapan K.
Workers found more dinosaur fossil pieces later at
In the late 1920s, two partial skeletons of large, long necked plant eating dinosaurs turned up. Paleontologist Heber A. Longman named them Rhoetosaurus and Austrosaurus.
Dinosaur Research Today:- During the past two decades, many scientists have turned to the study of dinosaurs as a career despite the low pay. Also, more museums and universities have developed dinosaur research programs. So the number of known dinosaur species has doubled since the 1960’s, and our under standing of dinosaurs has greatly increased. New dinosaur species continue to be described at a rate of about one every seven weeks.
Hohn R. “Jack” Horner has discovered hatchling duckbilled dinosaurs, dinosaur eggs, embryos, and nesting grounds in
Farther south, in
Spencer G. Lucas and Adrian Hunt started several projects in
In 1947, an
In the early 1970’s Robert T. Baker drew on the work of anatomist Gerhard Heilmann and paleontologist Hohn Ostrom and argued that dinosaurs were not slow moving, but rather warm blooded, active, mobile creatures. He also argued that dinosaurs are the direct ancestors of birds.
The eastern half of
In the past,
James M. Clark, Rene Hernandez, and other paleontologists are now working a site of roughly Middle Jurassic age in
Bonaparte has also discovered dinosaurs from the Middle Jurassic in
The Cultural Revolution of the 1960s stopped most research in
The Polish Mongolian Paleontological Expeditions of the late 1960s and early 1970s returned to the
Eric Buffetaut has participated in several recent discoveries. In the late 1970s, while searching for crocodile remains in
Because much of the
Recent studies by
In 1970s, French paleontologists discovered interesting Middle Cretaceous African dinosaurs near the Tenere Oasis in the southern
Ralph Molnar of the
Also working in
No paleontologist doubted that dinosaurs lived in
Some of the most interesting work is not always the discovery of ever odder dinosaurs. For some paleontologists, the most interesting work is the analysis of fossils gathered years, decades, or ever a century ago. We do not know what piece of fossil may lead to new insights into dinosaur behavior or evolution. With the continuing work of dedicated scientists, our knowledge of these wonderful creatures increases almost daily.
DINOSAUR CLASSIFICATION AND EVOLUTION
Dinosaurs ruled the world during the Mesozoic Era, which is divided into three Periods. During the Triassic Period, dinosaur ancestors were evolving. In the Late Triassic, the world saw the first true dinosaurs. In the Jurassic Period, many different types of dinosaurs had evolved.
Paleontologists study the different kinds of dinosaurs to find their relationships to other dinosaurs and to find the ancestors of the dinosaurs. This can tell scientists much about evolution. It can also tell them some things about the world the dinosaurs lived in. Dinosaurs that could migrate were similar, but those dinosaurs that were isolated evolved differently from their relatives on other continents.
In order to study dinosaurs, scientists use a system of classification called taxonomy. This groups related animals into species, genera, families, infraorders, suborders, orders, classes, phyla, and kingdoms. Animals are grouped together because of common traits that they inherited from common ancestors.
Because scientists have incomplete information for dinosaurs, groupings may change when new information is found. So each new dinosaur fossil that is discovered could be a key that unlocks some of the information about dinosaur evolution and ancestry.
The Linnaean System of Classification:- In the 1750’s, Swedish botanist Carl von Linne (who is known by the Latin form of his name, Linnaeus) developed a system to classify all living things. Each living thing has two scientific names, a genus and a species name. The scientist who first describes a new organism (any living thing) names it. Since Linnaeus began using this system, over a million species have been named.
A scientific name is given in the Linaean System because living organisms are called different thing is different languages. The house cat, for example, is die Katze in German; le chat in French; but English, French, and German biologists call it Felis catus.
In choosing a name, a scientist may highlight an interesting feature of the organism or may name it in honor of a person or the place it was found. So, the enormous meat eating dinosaur Tyrannosaurus rex is the “tyrant lizard king’ that reigned over other dinosaurs.
In the Linnaean System, similar species are grouped into a genus, similar genera into a family, similar families into an order, similar orders into a class, similar classes into a phylum, and similar phyla into the genus Canis. Vulpes, the fox genus, and Canis are both in the dog family Canidae. Canidae and Ursidae, the bear family, are part of the order Carnivora (meat eating animals). Carnivores and people are in the class Mammalian (all mammals). Mammals and fishes are in the phylum Chordata (animals with back bones, or chordates). Chordates and corals are members of the kingdom Animalia (animals). These categories are known as taxa (singular: taxon), and the study of these classifications is called taxonomy.
Classification and Evolution:- After Charles Darwin published his theory of evolution, biologists began to understand why organisms fall into natural groupings. For example, species in the dog genus Canis look like one another because they all had a common ancestor. Foxes (genus Vulpes) and dogs (genus Canis) do not look as much alike because their common ancestor was farther back in time. The farther back a common ancestor lived, the longer its descendants have had to evolve and change.
It is almost impossible to prove that two species share a common ancestor. But by making an extensive list of characteristics scientists can show how likely it is that two species are related. The more traits two species share, the more likely they are closely related and got those traits from a shared ancestor.
For example, both sparrows and bats have arms and hands that are wings, but sparrow wings and bat wings are much different. Sparrow wings and bat wings evolved separately, and not because of a common ancestor. This is called convergent evolution. On the other hand, the wings of sparrows, eagles, ostriches, and all other birds are alike. This shows that today’s bird’s species are closely related and came from a common ancestor.
Dinosaurs as Archosaurs:- Only a few dinosaurs are known from complete or nearly complete skeletons; almost half of the known species are based only on teeth or bone fragments. The shapes of bones are used for dinosaur classification. Only the hundred or so dinosaurs for which good remains are known can be studied for relationships.
Bones are rarely fossilized. Living things usually decay and vanish after death. It is difficult for paleontologists to describe an incomplete fossil skeleton and to decide what the animal looked and acted like from just a few fossilized remains. The discovery of a new dinosaur or new fossils of a poorly known dinosaur may change the family tree. We will never know all the different dinosaur groups that lived, so their family tree will always be incomplete.
Dinosaurs are classified as reptiles, but all reptiles do not form a single clade (a group that includes a common ancestral species and all the species that descended from it). There are two reptilian clades. One clade includes all living reptiles, dinosaurs, ichthyosaurs, plesiosaurs, and birds (the Sauropsida). The other clade is the mammals and the extinct mammal like reptiles (the Theropsida).
Crocodilians and birds are more closely related to each other than either is to lizards and snakes. They are part of a smaller sauropsid clade, the Archosauria. Lizards and snakes are in the clade Lepidosauria. Archosaurs had a large opening in the front of each eye. As the many groups of archosaurs evolved, this antorbital fenestra (“window in front of the eye”) sometimes closed (in crocodilians and the later plant-eating dinosaurs) or merged with the nostril (in pterosaurs). It was the largest opening in the skull of the large predatory dinosaurs, such as Allosaurus and Tyranosaurus.
The earliest archosaurs are found in Permian rocks, formed before the Mesozoic Era began. In the beginning of the Mesozoic, when animal life was recovering from the worst mass extinction I the world’s history, the archosaurs expanded and quickly spread. Most of those first archosaurs were extinct by the end of the Triassic period, but the Pterosauria, Saurischia, and Ornithischia survived to the end of the Mesozoic, and the Crocodilia survived to the present. Birds have not been found in the Triassic, although some puzzling Triassic birdlike animals have recently been discovered in Asia, Europe, and
Archosaurs Evolve:- Two important evolutionary changes took place among the archosaurs. They changed from sprawling, lizardlike animals to animals that walked with their legs held directly under their bodies. The other change was from a cold blodded, lizardlike metabolism (the way a body uses energy) to a warm blooded, birdlike metabolism. These changed did not take place in all archosaurs, but they happened in the dinosaurs. Corocodilians are the only surviving group in which they did occur.
Warm bloodedness may have appeared early in the dinosaur bird clade, so that almost all dinosaurs were warm blooded. This trait may have been inherited from a common ancestor dinosaurs shared with birds. Or, these changes may have happened after dinosaurs and birds separated, so that only a few advanced predatory dinosaurs were warm blooded.
The ancestors of dinosaurs developed a stronger ankle. This kind of ankle occurs in pterosaurs, dinosaurs, and birds. Lagosuchus, Lagerpeton, and Pseudolagosuchus were small, bipedal (they walked on two legs) archosaurs with advanced ankles and other features that suggest they were closely related to dinosaurs.
Harry Govier Seeley split dinosaurs into two groups, the Order Saurischia (“lizard-hipped” dinosaurs) and the Order Ornithischia (“bird-hipped” dinosaurs). Both orders probably had a common ancestor that lived sometime during the Middle Triassic. Birds belong to the saurischians dinosaur clade.
As in all land animals, there were three bones in each side of the pelvis. The left and right ilia (singular: ilium) firmly gripped the spine in the sacrum. The left and right pubes (singular: pubis) extended down beneath the ilia. The left and right ischia (singular: ischium) extended down and back beneath the ilia and behind the pubes. In some dinosaurs, the pubes extended down and forward, as they do in lizards. This is why Seeley called them saruischian, or “lizard-hipped” dinosaurs. In other dinosaurs, the pubes extended down and back, running beneath and parallel to the ischia, as they do in birds. Seeley called these dinosaurs’ ornithischian, or “bird-hipped” dinosaurs.
Ornithischian dinosaur pelves (the plural of pelvis) developed from evolutionary changes of the primitive saurischians pelvis. Ornithischians also had other traits that grouped them together: a bone, called the predentary, was at the front of the lower jaw. Also, an “eyelid” bone rimmed the upper part of the eye socket.
Some dinosaurs were neither saurischians nor ornithischians. The earliest, most primitive dinosaurs, such as staurikosaurus and Herrerasaurus, fit into neither order. They were too specialized to be the direct ancestors of the dinosaurs.
Interpreting Dinosaur Fossils
Our knowledge of dinosaurs comes from what they left on earth as fossils. But very little dinosaur material has been fossilized by nature, and the nature itself often becomes the fossils’ enemy. Wind and weather can damage fragile fossils, but erosion also uncovers them for collectors and paleontologists.
Scientists study dinosaur skeletons to learn about animals’ behavior and appearance. The skull is especially important. A dinosaur’s teeth can tell us whether it was an advanced or primitive dinosaur, whether it ate plants or meat, or even whether it ate soft or tough plants. Its skull will tell if it had a large or small brain or if it had good or bad eyesight, hearing, and sense of smell. The shape of a dinosaur skull can also tell us what other dinosaurs it was related to and where it fits in the family tree.
Though the skull is important, paleontologists can tell much about a dinosaur skeleton without a head; many skeletons are found without skulls. And there are other clues that dinosaurs left behind, all giving information about their lifestyles and habits. Scientists have discovered dinosaur track ways (fossilized footprints), nests, and eggs. But even with this information, there is much that will never be known. The fossil record is incomplete and can be misleading. Paleontologists continue to search, hoping to uncover other clues that will give them more information about dinosaurs.
How Dinosaurs Became Fossils:- The term fossilized is important. It is not the dinosaur bones themselves that paleontologists find, but their stony replicas. Fossil bones are created by the slow replacement of bone molecules with the molecules of minerals in ground water. This process sometimes preserves even the delicate cell structure of the bones. Other times the bones dissolve completely and only their imprint is left on the rocks.
Teeth and bones are the most durable parts of a vertebrate’s body. They may survive long after the animal’s soft parts have rotted or been eaten. Except for fossilized footprints, skeletal remains are the most common fossils. Unfortunately, few animals ever become fossilized, compared to the millions that lived.
Animals seldom die where they can be fossilized. A recently deceased animal that remains above ground will be dissolved by the chemicals in soil and converted into plant food. This is why the bodies of even large animals are seldom found in the woods and why fossils are most often found in deserts and other “bone-dry” places where there are not many plants.
In order for a skeleton to become a fossil, a layer of sediment must quickly cover the body. This prevents the skeleton from being destroyed by other animals or nature. Over the following thousands and millions of years, this sediment hardnes into a protective layer of rock, such as shale, silt-stone, mudstone, or sandstone.
Dinosaur bones could have been covered by sediment in still water, such as at the bottoms of lakes, slow moving rivers and river deltas, shallow seas, and seacoasts. The sediment could also have been brought volcanic ash falls. The places where conditions are right for skeletons to become fossils are only a small percentage of the world’s land area at any time. Many species of dinosaurs lived where no fossils could form. Partly for this reason, there are many evolutionary “missing kinks” between groups of dinosaurs. So there is an incomplete picture of dinosaurs from the fossils record.
Problems with the Fossils Record:- The fossil record can give us large amounts of knowledge. But there are many other ways that the fossil record is incomplete or misleading. Scientists must keep these problems in mind when they are reading the fossils record to come to conclusions about dinosaurs and their lifestyles.
Large, heavy bones are more likely to be preserved than small, lightly built bones. So, although small vertebrates usually out number large, fossils of small vertebrates are scarce. This might seem to suggest that big dinosaurs dominated the landscape and that were fewer small animals. This was probably not the case.
For dinosaur fossils to be found, the rocks where the fossils are located must be accessible. Many dinosaur bearing formations were eroded by wind and weather long before humans were around, so their fossils have been lost forever. Other dinosaur bearing formations are buried beneath hundreds of feet, even miles, of rock. These fossils are waiting to be excavated in the future. Only dinosaur bearing formation that are now at the earth’s surface are ready to be researched. So there is much information about the fossils record that has already been lost to erosion, but there is still much that today’s paleontologist will never be able to find and evaluate.
We can also get a wrong idea about dinosaurs when scientists and paleontologists make mistakes. In the past, researchers were interested mainly in well preserved skeletons that could be displayed in museums, so they sometimes ignored dinosaur bones unless they were new dinosaurs. Other times, they removed only the most interesting parts of the skeleton, such as the skull. They may have done this because they did not have the time or the money to excavate the whole skeleton, so they left the rest to erode.
Some museum specimens are useless because important information was recorded incorrectly or not at all. Dinosaurs have occasionally been mounted in museums with the bones in the wrong places. Museum workers have sometimes used too much plaster, restoring missing parts incorrectly. This may have mislead other researchers who relied on the published drawings and photographs of the restored skeletons. Modern methods of fossil collection and preparation have eliminated many of these problems with newly collected material. But museums have many fossils in their collections that need to be restudied.
So, everything we know about dinosaurs comes to us through an incomplete fossil record and the imperfect people who investigate it. But there is still much information that this fossil record gives us.
Dinosaur Appearance and Behavior:- Dinosaurs with almost complete fossil skeletons give us clues about what they were like. We get a good idea of the dinosaurs’ size, weight, and appearance in life. The cell structure of fossilized dinosaur bones can tell us about the biology of a dinosaur. We then have information about how rapidly they grew, and perhaps about whether they were warm blooded or cold blooded. Fossilized bones sometimes leave evidence of bone diseases and the tooth marks of predators. Muscle tissue is almost never preserved (only two good “dinosaur mummies,” with soft parts intact, have been discovered). But we can still tell how dinosaurs moved from the traces of ligaments and muscle scars on the bones.
Dinosaurs’ teeth can tell us what kinds of foods they ate. Occasionally the actual stomach contents are preserved, so scientists can study what a dinosaur had for its last meal. The smooth “stomach stones” with which some dinosaurs ground up their foot are sometimes preserved, and even fossilized dinosaur droppings, which are know as coprolites, have been found. All this gives us more information on dinosaur diets.
Fossilized skin impressions can be seen on very well preserved skeletons. The fine grained sandy rocks of
Scientists study locations and distribution of dinosaur bones for information about the dinosaurs’ environments. The direction in which bones are pointed and the way they are arranged in dinosaur bone beds are clues about the size and strength of rivers dinosaurs had to wade through. Scientists compare the number of different types of dinosaurs from one location to find out about dinosaur habits and life styles. For example, if there were few predators and many animals that would have been their prey, it would show that the predatory dinosaurs had a quick metabolism and were probably warm blooded.
Dinosaur Tracks:- Fossilized dinosaur footprints are most common than dinosaur skeletal remains. This is not surprising because each dinosaur could have left hundreds of thousands of prints over its lifetime. Unfortunately, footprints give few details about what the dinosaur looked like and what species it belonged to, though the skin texture of the soles of its feet is sometimes imprinted. The tracks can tell us an enormous amount about how the trackmakers walked, curised, ran, sprinted, and even swam.
We know from their footprints, for example, that large theropod dinosaurs either roamed by themselves or in small groups. Smaller dinosaurs, both plant eaters and meat eaters, often gathered in herds that left many directionless footprints. Large sauropods also probably lived in herds. After more study by paleontologists, track ways may show that dinosaurs migrated along thousand mile long “highways” in search of food.
By measuring stride lengths and foot print sizes, and comparing them with modern animals, it is possible to estimate how fast dinosaurs walked and ran. Typical walking speeds were about four or five miles per hour, though large sauropods may have walked two or three miles per hour. Since animals do not run at top speed for any length of time, tracks of fast running dinosaurs are rare. Estimated theropod speeds may be more than 30 miles per hour, and ornithomimids may have faster than ostriches.
Dinosaur Eggs:- Fossilized dinosaur eggs were first unearthed in
But the recent discoveries of dinosaur nests, nurseries, eggs, embryos, hatchlings, nestling, and juveniles in
Dinosaur Skeletal Structures:- Dinosaurs are known for the special skeletal structures they evolved. These include the horns and frills of the ceratopsians; the sailbacks of certain iguanodontids and theropods; the domed skulls of the pachycephalosaurians; the cranial crests of the hadrosaurs and certain theropods; and the plates and spines of the stegosaurians and ankylosaurians. These special skeletal structures would have been bold and obvious, so these structures may have been for display. Many also had other uses, including regulation of body heat, making noise, and defense.
Sight was an important sense to dinosaurs; their eyes were large. Dinosaurs were closely related to birds and crocodiles; both see colors and have a wide range of visual signals. So, these special skeletal structures of dinosaurs may have been brightly colored or boldly patterned. Closely related but different species may have been differently colored so they could be told apart during mating season.
Some of these structures, such as stegosaurian plates and ceratopsian frills, were made of thin bone that had many passages for blood vessels. Blood must have run through these passages, either to cool the animal off (if the dinosaur were warm blooded) or to warm it up (if the dinosaur were cold blooded). By regulating the blood flow to these structures, a dinosaur could regulate heat loss or heat gain and maintain a reasonably constant body temperature. The dinosaur may also have been able to change the structure’s color by changing the blood flow. This would have given dinosaurs a way of expressing their emotional state to others of their kind.
Birds and crocodiles have excellent hearing, and their relatives the dinosaurs probably did, too. Some dinosaur skulls have the delicate bony structures of their middle and inner ears preserved. By examining these, scientists can confirm that most dinosaur groups could hear very well. Since that is true, they may have been able to vocalize. The head crests of the lambeosaurines were part of their nasal passages. An animal inhaled air into its crest, which then went down through the back of its head into the lungs. This was a very complicated pathway, but it may have been used for making sounds. The lambeosaurine could have inhaled air and vibrated its looping nasal passage, emitting a deep, low frequency call. As far as we know, no two lambeosaurines had exactly the same crest shape, so no two would have made the same call. Their crests may have vocally distinguished individuals from on another.
The function of the horns of ceratopsids seems obvious: To fight an attacking tyrannosaurid. Also, rival ceratopsids probably locked horns in shoving matches over mates. Today’s moose and elk use their antlers like this and fight predators by using their sharp hoofed feet, not their antlers. Ceratopsids could also have used their sharp beaks to inflict painful, sometimes fatal wounds on predators.
It is difficult to understand that the world was a far different place 65 to 240 million years ago and that it was populated by huge and strange looking creatures. All the large animals in today’s zoos, from elephants to zebras to kangaroos (except crocodiles), evolved well after dinosaurs were gone. We are fortunate that some of the dinosaurs left their traces in rocks, which scientists have been able to study and compare with living animals. Scientists can then make educated assumptions about dinosaur lifestyles. In a world with a history that spans four and a half billion years, perhaps the most interesting thing about dinosaurs is that we have been able to learn anything about them at all.
Dinosaurs had not arrived as the Permian Period ended and the Triassic began. The earth’s land and climate were changing, the ancestors of the dinosaurs were evolving, and many plants and animals were becoming extinct. Because these events took place, dinosaurs became rulers of the earth by the Jurassic Period.
At the beginning of the Triassic Period, all land was joined as a single large mass called Pangaea. It stretched nearly pole to pole. The only block of land not joined to Pangaea was southern
Large and masses are more sensitive than oceans to heating and cooling. During a hemisphere’s summer, a large land mass warms the hemisphere. It then becomes the center of cooling during the hemisphere’s winter. This produces air pressure changes, which result in strong seasons. Although scientists disagree about the exact climate, it seems the Triassic started out cool and dry and became warmer, which rainy summers and drier winters. This became a monsoon weather pattern, as in south
This weather pattern affected the soil and land. Vertisols are fossil soil produced by a wet season followed by a dry season. This soil is found in Triassic formations. Red beds are also widespread in Triassic formations. Red beds get their color when iron in the soil oxidizes (rusts) because of warm, some what dry weather.
Triassic plants included ferns, conifers and cycads. These plants would have needed warm, most plants were becoming extinct and other was evolving. The Late Triassic plant Sanmiguelia may be the ancestor of flowering plants, though it did not become established until the Early Cretaceous.
Dinosaurs did not appear until the Middle to Late Triassic. But many other animals lived in the Triassic world. The therapsids were mammal like reptiles that ruled the earth before dinosaurs. They included the labyrinthodonts, the late survivors of the early amphibians; dicynodonts, the turtlebilled plant eaters; and cynodonts, the ancestors of mammals.
Triassic Map:- Lystrosaurus, a dog-size dicynodont, was the ruling animal at the beginning of the Triassic. Scientists have found its fossils in Asia, Africa, South America, and
Archosarus first appeared in the Late Permian as a minor part of the fauna. Dinosaurs, crocodiles, pterosaurs, and thecodonots all belong to the group Archosauria. The thecodonts were the first archosaurs. They were divided into five groups: the proterosuchians were the first thecodonts; the rauischians were crocodile like; the phytosaurs lived in water; the aetosaurs were the only plant eaters; and the ornithosuchians were probable descended from some type of proterosuchian. Proterosuchus was a thecodont from the earliest Triassic. It was almost the size of a modern crocodile.
Halfway through the Early Triassic, the Lystrosaurus fauna was replaced by other dicynodonts, cynodontsn, and archosaurs. Important archosaurs that appeared were Erythrosuchus, a large meat eater; and Euparkeria, a fast, small meat eater. Euparkeria was important because it had features of later archosaurs; it stood more upright, it had armor, and it had no teeth on its palate. Also appearing around this time were the rhynchosaurs. This group of land herbivores were close relatives of the archosaurs and were among the most plentiful plant eaters in the Middle and early Late Triassic.
The Middle Triassic is important as a time of transition. The archosaurs were becoming more important and more meat eaters were emerging, including many kinds of small, crocodile like archosaurs. Also showing up were the large, four legged predators, the Prestosuchidae and Rauisuchidae, and the small land carnivore Gracilisuchus. All these were members of the line leading to crocodiles.
The ancestors of the dinosaurs were beginning to be important. Lagousuchus, Pseudolagosuchus, and Lagerpeton were tiny meat eaters with ling lets. They were close to the common ancestors of dinosaurs and pterosaurs, with ankles like later dinosaurs.
The earliest dinosaurs appeared in rocks that date to the late Middle Triassic or earliest Late Triassic. These were found in the Santa Maria Formation of Brazil and the slightly younger Ischigualasto Formation of Argentina. However, there are three toed, dinosaur like footprints from as early as the end of the Early Triassic.
The earliest dinosaurs were rare. The Middle to Late Triassic was a time dominated by rhynchosaurs. Big dicynodonts and medium to large cynodonts were in decline. The non dinosaur archosaurs included the mostly meat eating rauisuchids and proterochampsids; and the armored, plant eating aetosaurs. A Late Triassic rauisuchid was Postosuchus. The earliest dinosaurs were Staurikosaurus, Herrerasaurus, and Pisanosaurus. Soon after, the herbivorous prosauropods and the carnivorous theropods appeared.
Half way through the Late Triassic, a major change happened. New groups of phytosaurs and aetosaurs appeared, and a number of herbivore groups, including dicynodonts and rhynchosaurs, disappeared. Where this happened, theropod (meat eating) dinosaurs appeared in larger numbers. Larger theropods were also emerging.
In the latest part of the Late Triassic Period, dinosaurs increased. In the latest Triassic beds in Europe, South America, and southern
At the end of the Triassic, a major extinction occurred. All archosaurs became extinct except for the dinosaurs, crocodilians, and pterosaurs. These extinctions probably happened because Pangaea was moving north and breaking apart, which caused the climate to change. Different dinosaurs then arose during the Early Jurassic, such as the two crested theropod Dilophosaurus. Scutellosaurus, an armored ornithischian, and Vulcanodon and Barapasaurus, the first sauropods, also emerged.
In the Early Jurassic, except for the sauropods, few new major groups of dinosaurs appeared. Instead, the existing dinosaurs of this time mostly increased in number and diversity. They became, by the beginning of the Jurassic, the most important land animal.
Dinosaurs take over the world
By the Middle and Late Jurassic, dinosaurs had taken over the world. There were herds of Apatosaurs; each adult was as large as five or six elephants. Allosaurus, a two ton meat eater, waited in the bushes for its next meal; it needed to eat often to fill its appetite. Bony plates protected slow, steady Stegosaurus, which had little fear of predators. The land quaked with dinosaur footsteps. Dinosaurs controlled this Jurassic world.
Pangaea continued to break apart in the Jurassic. It was splitting both north and south, and east and west. The land masses were beginning to resemble the shapes they have today. The
The northern part of the Atlantic Ocean began to open during the Jurassic, and it separated Laurasia into eastern (Europe and Asia) and western (
All these changes in the continents changed the way the ocean waters flowed. Cold ocean currents in the southern hemisphere produced temperate climates in what is now South America, southern Africa, Antarctica, India (an island off eastern Africa), and Australia. The rest of the world was also warm and moist, and the Triassic deserts deserts were shrinking and were gone by the Late Jurassic. There were no polar ice caps.
In this dry and semi dry Jurassic landscape, conifers dominated wherever trees grew. Except for dinosaurs, the Jurassic plants and animals were much like those of earlier times. There were many ferns, tree ferns, cycads, ginkgos, and horsetails. Grasses had not yet evolved, but some ferns may have served as low ground cover.
Pterosaurs glided and flapped their way to feeding grounds. There were two types of pterosaurs, ones with tails and ones without. The Pterosaurs with tails did not last past the Late Jurassic; the pterosaurs without tails survived into the Cretaceous. Crocodiles, which replaced the phytosaurs of the Triassic, lurked in the undergrowth near water. Mammals, the descendants of the therapsids, were still running around. They were mostly shrewlike creatures that were four to five inches long, eating insects or chewing fruits and seeds. New insects were also evolving, including the ancestors of earwigs, flies, and bees, among others.
The mammallike reptiles that were so important in the Triassic were gone by the Middle Jurassic, as were the rauisuchids and other archosaurs. Late in the Jurassic, small lizards, frogs, and salamanders crawled around under the cover of plants. Turtles, though not large, had also appeared. In the seas, corals, clams, and snails flourished, as did sharks and the marine reptiles, including plesiosaurs and ichthyosaurs.
The landscape provided food, forage, and home for the dinosaurs. As the land became greener in the Late Jurassic, the sauropods gained the advantage. They reached from
The large plant eaters such as Apatosaurus moved constantly, perhaps like elephants feeding almost around the clock. They probable destroyed plant life as they grazed through an area, but at the same time they opened the ground to more sunlight for new growth. Migration of the sauropods was random and only loosely tied to a region. They may have had separate areas for laying eggs, where the young would hatch away from the adults. The large herds probably were mostly adults, with the adults protecting the young.
The large sauropods browsed at the tops of trees for food, where no other dinosaurs could reach. The smaller plant eaters ate ground cover and shorter brush. Some, such as Stegosaurus, probably reared up on their hind legs to get higher brush. The small meat eaters probable ate lizards and scavenged meals from other animals. Large meat eaters would have eaten smaller dinosaurs and even attempted to kill a sauropod, perhaps a youngster that strayed from the herd.
Dinosaurs of the Late Jurassic in
Archaeopteryx flew from conifer tree to conifer tree. It was an ancestor of modern birds. A coelurosaur dinosaur of the Middle Jurassic may have been its ancestor.
More and more kinds of dinosaurs were evolving in the Middle and Late Jurassic Period, but the most important dinosaurs of this time were the sauropods. These immense creatures roamed the earth searching for food to sustain their enormous size. The earth did provide for them, though there are still some questions scientists have about their diets. These animals were the most successful dinosaurs, with their numbers growing rapidly. They were truly the masters of their universe.
DINOSAURS BUILD THERE EMPIRE
The earth was still in the process of change as the early Cretaceous began. The land masses were drifting and the climates were changing. These changes affected the plant and animal worlds. Dinosaurs were becoming more plentiful and many more types were evolving. Some of the more fanciful dinosaurs with unusual crests and frills appeared. In contrast to earlier periods, dinosaurs at this time were different in different areas. Dinosaurs in
When the Early Cretaceous Period began 144 million years ago, the huge land mass known as Pangaea had already started to separate. Laurasia (present day North America, Europe, and Asia) was almost completely separated from Gondwanaland (present day South America, Africa,
The Early Cretaceous world was very warm. There were wet and dry seasons rather than summer and winter. Most areas of the world were covered by tropical and semitropical jungles. The low growing plants were ferns and fernlike vegetation. Plants of medium height were the cycads and their relatives. Treelike plants over 60 feet tall were mostly tropical conifers, ginkgos, and czekanowskian trees (an extinct group of trees with long, needlelike leaves). Fast growing angiosperms flowering plants appeared for the first time.
Surprisingly modern looking frogs, salamanders, turtles, and crocodiles lived in the rivers and lakes. Snakes had only begun to evolve, but there were many lizards, along with primitive furry mammals. All these animals provided food for small predatory dinosaurs. The long tailed pterosaurs from the Jurassic were replaced by short tailed ones, including Anhanguera, Tropeognathus, and Tupuxuara.
As Laurasia and Gondwanaland broke into smaller continents, dinosaurs on the separated continents evolved differently.
Other plant eaters from this area include the sauropod pelorosaurus, with a long, slender upper arm bone; it seems to have been a brachiosaurid. Craterosaurus is the only known stegosaur; the ankylosaur Hylaeosaurus seems to have been quite a bit more abundant than Craterosaurus. Armored dinosaurs were short and probable ate lower growing plants. The small herbivore Stenopelix also lived during this period. It was possibly the earliest known ceratopsian. Yaverlandia is thought to be a very early pachycephalosaur.
Since North America was still joined to Europe (via Greenland), it had dinosaurs quite similar to those of
Large ornithopods were not common in the Early Cretaceous of eastern
Preying upon these herbivores were large and small theropods. Kelmayisaurus was megalosaurid that probable ate the armored Wuerhosaurus. Chilantaisaurus maortuensis could easily have held a struggling Probactrosaurur in the grip of its powerful front limbs.
Dinosaurs from the Early Cretaceous of Gondwanaland are less well known than those of Laurasia and show some intriguing and unexpected differences. Sauropods remained prominent in the southern hemisphere sespite their drastic decline in the northern hemisphere. Large ornithopods were more scarce than their northern relatives; small ornithopods were common. Theropods in the South were often from families different from those in the North.
Dinosaurs from northern
In the early Cretaceous, many new dinosaurs appeared. They also greatly increased in number. During this period, dinosaurs not only maintained but also expanded their “empire”.
DINOSAURS ADVANCE AND RULE THE WORLD
During the Late Cretaceous, land and seas continued to change and move. The climate of the world changed toward cooler and more seasonal weather. New types of plants and animals were appearing. An amazing collection of dinosaurs had evolved. Some had become advanced, even caring for their young. Dinosaurs, at first plentiful, disappeared from the earth by the end of the period.
The continents continued to separate during the Late Cretaceous. North and South America moved west into the Pacific Ocean, and the North and
A shallow sea covered
Flowering plants spread rapidly throughout the northern hemisphere in the early Late Cretaceous, appearing first as small weeds. They quickly became the most important land plants. They provided a dense clutter of leaves, stems, and branches. In drier areas, flowering plants became underbrush. Able to grow rapidly after being eaten or trampled, flowering plants fed a larger number of animals.
During the early Late Cretaceous, the climate was warm. As the period came to a close, the average climate became cooler, but it was still much warmer than today. By the end of the period, the tropics were only in areas near the equator. The climate in the farther northern and southern hemispheres (and polar regions) became temperate and more seasonal, with cool winters and warm summers. Forests in the temperate zones became less tropical, with magnolias, sassafras, redwoods, and willow trees plentiful.
Dinosaurs remained the main large land animals. Smaller land animals included turtles, crocodiles, snakes, lizards, frogs, and salamanders. Mammals remained small, but mammals that gave birth to live young appeared for the first time.
Almost all Late Cretaceous flying birds were tiny. But pterosaurs became the largest flying creatures ever known. Ichthyosaurs became extinct, and mosasaurs became the main marine predators. These evolved from small to medium size monitor lizards. They shared the seas with plesiosaurs.
As many dinosaur species are known from the Late Cretaceous as are known from all the other periods together. In
Although the hadrosaurids are best known for their broad, horny, ducklike beaks, they are also famous for the different shaped crests on their heads. Perhaps used for vocalizing, the crests may also have identified male and female animals during mating season. Horns and frills evolved for the same reason in ceratopsians, with norns also used for combat and defense.
Plant eaters were eaten by fierce tyrannosaurids. Most of those known from
There were many small predators in
Eastern Asia especially
The most interesting dinosaurs discovered in
Small predators closely related to those in western North America abounded in eastern
The Gondwanaland continents had different Late Cretaceous dinosaurs. Almost all the Late Cretaceous Gondwanaland sauropods were titanosaurids. They were found mainly in South America, Africa,
Ceratosaurus:- This medium sized carnivore measured around 20 feet long and weighed up to 1,200 pounds. We do not know its exact range but fossils or indications seem to place it in the
What is unusual about this dinosaur is that it had a distinctive horn and two bony ridges on its skull that gave it a very fierce appearance. Its name means "Horned reptile." We do not know the exact reason for these horns, but it is somewhat likely that they served as displays to impress the females and possibly acquire either a "harem" or better breading rights through prime territories or some such much like Elk do today. In the same unusual vein this ancient reptile also was the only meat eater to have some armor. The exact function of the smallish armored bumps is unknown and again may have been due to a selection process of the females of the species who may have simply "liked it."
Another unusual feature is that unlike the T rex with two fingers or the Allosaurus with three fingers the Ceratosaurus had four fingers. They do not appear to be strong enough for grasping or tearing so they likely had the same function that those of the T rex did.
The teeth were very sharp and the structure of the jaws tells us this species likely sliced off large sections of its victim and possibly let them bleed to death before feeding.
Camptosaurus:- This early member of the iguanodontids has only one recognized species from
It is highly likely that this late Jurassic plant eater was a favorite prey of the carnivores like Allosaurus. Its name means "bent lizard" which is referring to the fact that the large thigh bone in the leg is curved in order to keep its legs further apart so that they could clear the wide rib cage. This dinosaur because of its anatomy and lifestyle probably spent most of its life walking on two legs. Its shape was rather bottom heavy but because of this the Camptosaurus was likely fairly maneuverable.
The teeth were much like grinders and likely preferred leafy vegetation which must have been retained in the cheek pouches until it was well chewed. They have often been found in the vicinity of Stegosaur and Camarasaur fossils so likely did not compete for food with them but liked the more sparsely available vegetation in this type of habitat so as not to compete with the much larger sauropods.
Camarasaurus:- A close relative of the brachiosaurs and titanosaurs, this late Jurassic dinosaur was apparently quite common in North America and some areas of Europe and
This sauropod was very heavily built and its head looked a bit like a cross between a bulldog and a horse. Its teeth were very unique in that they looked like ivory spoons and this dinosaur was obviously adapted to eating hard and fibrous plant materials. It likely bit off large portions of trees and bushes and swallowed them whole. The stomach was adapted to grinding up these large bites with the aid of stones. One prominent paleontologist commented that the Camarasaurus should be likened to an elephant but with its head on the end of its trunk and its teeth in its stomach.
Brachiosaurus:- One of the largest of all the sauropods was the Brachiosaurus. Who can forget that moment in Jurassic park when they first saw these magnificent creatures walk out of the water and stand up to browse from the top of a tall tree. The name means "arm lizard" which refers to the fact that its front legs or "arms" were longer than the rear legs. In size we find a true giant with lengths to 30 feet and weights of up to 80 ton with heads as tall as 50 feet above the ground.
Like many other large sauropods wherever weight could be saved it was. The head of brachiosaurs were very light weight and had many hollow areas throughout. This creature when full grow would have no competition for food and it is unlikely any carnivore or even a pack of carnivores would not even try and tackle this formidable plant eater.
The species were undoubtedly restricted to areas where tall trees grew in profusion. Fossil recorders from
Stegosaurs:- A Middle Jurassic to late Cretaceous dinosaur that almost everyone knows is the Stegosaurus whose name means "roof lizard" in mention of its plates running down its back that actually grew right out of its skin. In size we find a 20 to 30 foot length with body size similar to present day rhino's.
What a traumatic but fascinating scene in Walt Disney's Fantasia scene where the Stegosaurs gets killed to dramatic music by a Rex. Like its close relatives the ankylsaurs, this was a veritable tank when it came to defense. The plates on its back likely served the function of both heating & cooling as well as protection. They were apparently covered only with skin and many blood vessels rather than the horny protection originally thought. Around its throat was a network of bony studs. And its sideways pointing spikes that were over 3 1/2 feet long served as a powerful deterrent to any would be predator and may have been used as displays of dominance or courtship for mate selection.
For food these ornithischians most likely cropped low growing vegetation and possibly reared up to get higher growth in trees. Likely they were like a high lawn mower in that they ate everything within their reach before moving in any other plane or direction. Their stomachs have been described as being "moving fermentation vats that gave off enormous amounts of heat. This may explain another use of its plates, "as heat exchangers."
There were actually two species of Stegosaurs found in
Allosaurus:- Allosaurus:- Allosaurus was a very successful and abundant theropod dinosaur found through out the world from the middle Jurassic to late Cretaceous. In fact the largest carnivores ever found have been Allosaurs. In
The fossils have been plentiful and
It is speculated that the habitats frequented by North American Allosaurs was similar the plains of Amboseli in
Opisthias:- One of the most unusual lizards left on this planet is the Tuatara of New Zeland. Opisthias is an ancestor of this true "living fossil" and likely looked very similar. The Sphenodon's are currently represented by only the Tuatara, but that was not always the case. These "lizard-like" reptiles are not true lizards but are in fact a side-path of evolution that started in the Middle Triassic and continue down to the one species left today. Some relatives took to the water and became known as the pleurosaurs. Others were very similar to today's living fossil, in fact the same basic body type and lifestyle has been running virtually unchanged for nearly 200 million years.
Opisthias was a late Jurassic reptile that likely lived on small creatures like insects, worms, and small lizards in a lifestyle similar to modern day
Edmontonia:- A member of the Nodosaurs (which lack tail clubs or spikes) the four ton and 20 plus feet Edmontonia, meaning near Edmonton, was the closest thing to invulnerable in the Pacific Northwest dinosaur enclave that existed in the late Cretaceous North America. With its flexible armor, long and sharp shoulder spikes, and a two layer boney head it would be surprising that this subgroup of the ankylosaur dinosaurs were often preyed upon.
Climate and habitat at this time favored certain species of dinosaurs over others. Temperatures were up about 75 million years ago as was humidity. There were peat bogs and bald cypress swamps. Just back from these areas and inland were much flatter areas composed of river systems flowing to the seas. Many feeder and tributary stream channels crisscrossed the region and greatly affected the many dinosaurs in the area. Nearly half the plants found in this region were flowering. Cycads, ferns, katura trees, fern trees, and many types of conifers dominated the flora. The lower and tough members of these plants were preferred by Edmontonia and they were also likely to favor more open scrub land closer to the sea. It would not have been all that usual for them to occasionally see an elasmosaur far up the rivers looking for a fishy meal.
Einiosaurus:- Among the strangest looking of the ceretopsian dinosaurs was the Einiosaurus meaning "buffalo lizard." This late Cretaceous horned dinosaur has only been found in Northern Montana and in fact may have been relatively rare and in an isolated population separated from its more common contemporaries such as Triceratops or Styracosaurus. Not much is known about this recently discovered dinosaur but it likely behaved as did most of the other horned dinosaurs.
Daspletosaurus:- This coelurosaur, a likely ancestor of T rex, was truly a "frightful lizard." At 3 tons and over 30 feet in length this fast meat eating dinosaur was certainly the king of his late Cretaceous territory. In time Daspletosaurus was earlier than the rex but likely hunted the same prey in much the same manner. Another formidable carnivore at the same time and place was the somewhat more slender tyrannosaurid Albertosaurus. It is likely that little competition existed between these two species, much like lions and leopards coexist on the same African plain.
Like all tyrannosaurids this meat eating creature had only two arms, powerful jaws, and thick sharp teeth able take very large bites out of its prey. The size and depth of these bites may well have killed the victim from shear shock rather than actual attach trauma or blood loss.
Palaeosaniwa:- A close relative of monitor lizards Palaeosaniwa "before Saniwa" (another true lizard form the start of the mammals reign) was roughly the size of the more modern Komodo dragon. This puts it in the 10 to 11 foot and 350 pound range. The varanoid lizards of the past included forms like the ocean going mosasaurus which grew to lengths up to nearly 50 feet and Estesia which is believed to be venomous and related to today's Gila Monsters. Some scientists believe that snakes evolved from varanids like Palaeosaniwa but currently there is debate on whether that is the case or not.
Monitor lizards are true opportunists. They will usually eat almost anything from worms and fish to mammals and carrion. Some like the Komodo are ambush hunters and some are simply opportunists that will eat literally anything that is edible and will fit in the mouth. It is very likely that Palaeosaniwa lived a lifestyle very much like today's more modern but not very much changed from their earlier ancestors.
Corythosaurus:- This hadrosaur from the late has a crest much like Grecian warriors and thus its name means "Corinthian helmet lizard." It is closely related to Iguanodon and is called a duckbill dinosaur because it had no teeth in the front of its mouth and instead had a horny duckbill look. The teeth started way back in the jaw which is highly unusual as plant eating dinosaurs as whole just swallowed plants whole and let the stomach digest the mass. In addition these teeth were self sharpening and self renewing.
There has been a little debate as to how much time the duckbill dinosaurs spent walking on 2 legs versus all 4 and no real determination has been made. But the shape of the front feet indicates that they certainly could walk on all fours. There has also been much speculation on exactly what the high crest on the head was for. Modern research with cats can x rays seem to show that the hadrosaurs used these unusual shaped head ornaments to produce various sounds for either communicating or attracting mates or both. One can well imagine that several herds of different hadrosaurs may well have sounded like an unruly orchestra warming up with a clashing of different sounds. It was likely to either attract or drive of the meat eaters of the day depending on whether they were very hungry or music critics.
Ornithomimus:- Meaning "bird mimic" this extremely fleet ostrich dinosaur was about the size of or slightly larger than today's flightless ratite ostriches. At fifteen feet or so in length and over 300 pounds of speed these Cretaceous omnivores were perhaps the fastest family of dinosaurs ever seen on this planet. Close relatives were Struthiomimus, and who can forget that scene in the movie
Ornithomimus had a toothless jaw and what can only be described as a horny bird like beak. Because of their large brain size relative to other dinosaurs and their large eyes it is thought that they were among the most advanced dinosaurs ever to come onto the scene.
Parasaurolophis:- Truly one of the most unusual looking of all dinosaurs this duckbill dinosaur's name means "like or beside Saurolophus" and was a member of the hadrosaur lambeosaurid family. Very few skeletons of this trombone crested late Cretaceous dinosaur have been found and it may have been much rarer than its more common cousins but was definitely in parts of Western Canada, Utah, and New Mexico. This plant eating Ornithopod ran on two legs but likely browsed on all four and was at least 33 feet long and a head crest of 5 to 6 feet that was possibly attached to the neck or back with a skin frill.
It is highly likely that the crests on all the hadrosaur family dinosaurs was used to sound alarms, troll for mates, and generally communicate with each other. It is thought that they were all very social animals and possibly migrated together in large herds for protection from the many hungry carnivores just waiting for an opportunity for a duckbill steak.
Goniopholis:- A late Jurassic reptile closely related to the dinosaurs with relatives still living today is the Goniopholis which means "angled scutes." This ancient crocodilian looked very much like many of the crocs found today.
Many people think only that various dinosaurs populate the Mesozoic, but this actually a great distortion. As far as numbers and species count most of the know ancient world was likely to be very much like today in terms of turtles, tortoises, frogs, lizards, crocodilians, and their prey which consisted of insects, salamanders, and even small dinosaurs. The big boys of the dinosaurian persuasion were truly awesome and terrifying, but they were a very small part of the total picture ecological.
Ancient crocodiles have been around as long as the dinosaurs and from their first beginnings about 235 million years ago as long legged running archosaurs they have evolved out into a myriad of forms.