Prehistoric lizard dinosaurs. Dinosaurs. Tyrannosaurs are the most famous dinosaur species.

At each stage of the conquest of the planet Earth, there were certain animals that became a kind of "elite" of their time. These creatures were last word evolution, as well as the most perfect, most intelligent and energetic at that time. In this article we will talk about dinosaurs - reptiles that dominated the Earth 200 million years ago, or rather, about their names.

Rise of a dynasty

The name of dinosaurs can be translated from Greek as "terrible lizard". at one time they were the real crown of creation, the pinnacle of the development of reptiles. They ruled the ball for more than 100 million years, remaining the permanent rulers of the land. These creatures were numerous and varied. Not a single living soul of that time could compare with the terrible lizards.

The drama of the rise, rise, and extinction of the dinosaurs has captured the imagination of mankind ever since people learned of the existence of the so-called Great Age of Reptiles. These animals are still carefully studied, collecting materials and finding more and more fossil remains. Until recently, there was no consensus on the reasons for the death of the dinosaur dynasty, and even now scientific disputes are constantly flaring up on this topic.

A bit of taxonomy

Dinosaurs (pictures with names are presented in the article), like modern animals, cannot be considered by scientists chaotically. In order not to get confused in the variety of mice, snakes, elephants, cats, frogs, beetles, zoologists eventually divided all animals into certain groups, so to speak, put them on the shelves. Each of these groups combines creatures that are similar in structure and origin.

The main group of animals is their species, which combines many identical individuals. Related species are grouped into genera, or superfamilies. The genus, in turn, is combined into families; families - in units; squads into classes, and classes into types. For example, our species is a reasonable person, representing the genus of people from the anthropoid family. We belong to the order of primates, the class of mammals, and we represent a subtype of vertebrates from Here is such a simple logic!

It is worth noting that it is simply impossible to do without systematics. Otherwise, you can get confused, because at present there are several million species of different animals on the planet: this is an amoeba, a worm, a fly, and a person. In the same way, systematics works with reptiles under the name and the names of these creatures that lived in different eras are also different. All of them briefly reflect the essence of the behavior or life of the animal, as well as the features of its structure.

Just don't break your tongue!

As a rule, the scientific names of certain animals sound unusual for a simple layman, and some of them are generally impossible to pronounce. It is understandable: traditionally they are given in Latin or ancient Greek. For example, the name of dinosaurs usually reflects the features external structure these reptiles family ties animals, so that a specialist (zoologist, veterinarian, paleontologist) immediately understands what species he is dealing with.

Fish lizard and giant lizard

The name of dinosaurs in most cases has a component - "saur": allosaurus, brontosaurus, ichthyosaur, tyrannosaurus, etc. For example, the name "Brontosaurus" is translated as a giant, huge pangolin (see the picture below). In addition, Brontes was the name of one of the Cyclopes - ancient Greek mythical giants. The name "ichthyosaur" is translated from as a fish lizard: "ichthyos" is a fish, and "saurus" is a lizard. In this case, the name of this marine reptile indicates to us its appearance.

dogtooth

Sometimes in the names of terrible lizards you can find the word "dont", or "don". It translates as tooth. For example, one of the most famous dinosaurs of this group are cynodonts. These are animal-like lizards, which are the ancestors of modern mammals. The name of these dinosaurs reflects the essence of the structure of their dental system, and is translated as a dog-tooth: "cynos" - a dog, "dont" - a tooth.

flying dinosaur

The name of the dinosaurs that rose into the sky has an unusual component - dactyl. Translated from Latin the word "dactylos" means finger. The most famous flying dinosaur is, of course, the pterodactyl. Translated into Russian, this is a finger-wing: the ancient Greek word "pteron" is a wing.

Who are the Zukhi?

Often the name of dinosaurs includes the strange word "zuhiya". In principle, there is nothing complicated here either. This component is quite often included in the names of fossil reptiles: mesosuchia, eosuchia, pseudosuchia, pastosuchia, etc. So they call the ancient crocodiles or animals similar to them, since the ancient Greek word "zuhos" is a crocodile.

Tyrant among lizards

Of course, it is impossible to ignore the most popular dinosaur in the world - a tyrannosaurus rex. He and many of his other relatives are predatory dinosaurs. The names of these reptiles speak of their superiority over other animals, as if crowning these lizards. The word "tyrannosaurus" is translated from as a lizard-lord: "tyrannos" - master, lord.

Reptile family tree

As you already understood, reptiles are separate class vertebrates, subdivided into various subclasses. The most ancient and most primitive group of reptiles is the Anapsid subclass. Paleontologists have come to the conclusion that not a single representative of the anapsids has survived to this day, and their last representatives died out 200 million years ago!

From the very root of the anapsids, a branch separated, which was called the synapsid. Paleontologists refer our ancestors to this subclass of ancient reptiles - the ancestors of modern mammals, to which humans belong. Unfortunately, synapsids also died out, never having lived to see the heyday of their descendants.

This is another subclass of ancient reptiles, separated from the base of the ancient trunk - a subclass of anapsids. This branch was divided into two others - archosaurs and lepidosaurs. The former include crocodiles, flying and land dinosaurs, and to the second - currently living tuataria, snakes and lizards. Lepidosaurs also include already extinct aquatic called plesiosaurs.

Dinosaur species of this group lived in the late Jurassic period on the territory of modern North America about 150 million years ago. Paleontologists consider diplodocus to be one of the most easily identifiable dinosaurs. Moreover, this species is the largest of all dinosaurs known from complete skeletons found. Diplodocus were herbivores, and their huge size was a deterrent to the predatory lizards of those times - ceratosaurs and allosaurs.

Allosaurus - a thunderstorm of diplodocus!

Within the framework of this article, we will not be able to consider all types of dinosaurs with names, so we will only turn to the most prominent and famous representatives of these legendary giants. One of them is the Allosaurus. This is a representative of the genus of carnivorous dinosaurs from the group of theropods. Like diplodocus, allosaurs existed in the Jurassic period about 155 million years ago.

These creatures walked on their hind legs and had very small forelimbs. On average, these lizards reached a length of 9 meters and a height of 4 meters. Allosaurs were considered large bipedal predators of the time. The remains of these insidious creatures were found on the territory of modern Southern Europe, East Africa and North America.

Ichthyosaurs - legendary fish lizards

They represent an extinct order of large marine reptiles reaching a length of 20 meters. Outwardly, these lizards resembled modern fish and dolphins. Their distinguishing feature was big eyes protected by a bone ring. In general, at a short distance, ichthyosaurs could well be mistaken for fish or dolphins.

The origin of these creatures is still in question. Some paleontologists believe that they come from diapsids. This version is supported only by conjecture: apparently, the shoot of ichthyosaurs somehow branched off from the main diapsid stem even before this subclass split into archosaurs and lepidosaurs. However, the ancestors of these fish lizards are still not known. Ichthyosaurs died out about 90 million years ago.

Dinosaurs take to the sky

At the end of the Triassic period, the first flying species of dinosaurs appeared on the planet, which appeared unexpectedly in the fossil record. Curiously, they were already fully formed. Their direct ancestors, from which they developed all this time, are unknown.

All Triassic pterosaurs belong to the Rhamphorhynchus group: these creatures had huge heads, toothy mouths, long and narrow wings, and a long and thin tail. The size of these "leather birds" varied. Pterosaurs, as they were called, were mostly the size of both gulls and hawks. Of course, among them were 5-meter giants. Pterosaurs died out about 65 million years ago.

Tyrannosaurs are the most famous dinosaur species.

The list of ancient lizards would be incomplete if we did not mention the most majestic dinosaur of all times and eras - the tyrannosaurus rex. It's insidious and dangerous creature fully justifies its name. This creature represents a genus from the coelurosaur group and theropod suborder. It includes a single species - a tyrannosaurus rex (from the Latin language "rex" is a king). Tyrannosaurs, like allosaurs, were bipedal predators with massive skulls and sharp teeth. The limbs of Tyrannosaurus Rex were a complete physiological contradiction: massive hind legs and tiny hook-shaped forepaws.

Tyrannosaurus is largest view within their own family, as well as one of the largest terrestrial predatory lizards in the entire history of our planet. The remains of this animal were found in the west of modern North America. According to scientists, they lived about 65 million years ago, that is, it was in their century that the death of the entire dynasty of ancient lizards occurred. It was the tyrannosaurs that crowned the entire great era of dinosaurs, which ended during the Cretaceous period.

Feathered heritage

It is no secret to many people that birds are direct descendants of dinosaurs. Paleontologists saw in the external and internal structure Birds and dinosaurs have a lot in common. It should be remembered that birds are descendants of land lizards - dinosaurs, and not flying lizards - pterosaurs! Currently, two subclasses of ancient reptiles are "hanging in the air" because their ancestors and exact origins have not been established by paleontologists. The first subclass is the ichthyosaurs and the second is the turtles. If we have already dealt with ichthyosaurs above, then nothing is clear at all with turtles!

Are turtles amphibians?

And therefore it is clear that, considering such a topic as "Types of dinosaurs", one cannot fail to mention these animals. The origin of the turtle subclass is still shrouded in mystery. True, some zoologists still believe that they originated from anapsids. However, they are opposed by other pundits who are sure that turtles are the descendants of some ancient amphibians. And they do not depend on other reptiles at all. If this theory is confirmed, then a big breakthrough will occur in the science of zoology: it may happen that turtles will not have the slightest relation to reptiles at all, because then they will become ... amphibians!

Dinosaurs are the most numerous, diverse, and most famous order of extinct that have lived on Earth for over 150 million years. Mesozoic era in the history of the development of our planet is often called the era of dinosaurs. It was they who became the ancestors of modern.
These extraordinary lizards existed on all continents and were very diverse. Along with the giant brachiosaurs, there were small, chicken-sized Compsognathae.
Some species were - hunted or collected carrion. Others were herbivores - they ate plants and swallowed stones.
Prehistoric dinosaurs lived in pairs, laid eggs and raised offspring.
Depending on the species, they moved in different ways - on four or two legs. Some pangolins swam or tried to fly. Life in those prehistoric times was full of dangers, and the dinosaurs had to fight, to escape persecution, to be able to hide well. Therefore, the structure and appearance of dinosaurs is extremely diverse. Their torsos, heads, tails are covered with leathery scales, armored plates, spikes of various sizes and configurations. These are not only elements of intimidation of the enemy, but also protective measures or additional weapons in a cruel and merciless struggle for existence.
It has been 65 million years since these amazing animals became extinct. Until now, scientists cannot confidently name the reason that caused such a catastrophe. The memory of dinosaurs was preserved by stones, or rather, fossils. It is from the fossilized remains of animals and plants that scientists find during excavations that we learned about the existence of ancient pangolins. The researchers were able not only to restore the skeletons of these amazing ones, but also to reconstruct their life.
All known species dinosaurs were classified, grouped into families and groups according to the existing identical hallmarks. The main division occurs according to the composition pelvic bones into two orders - lizards and ornithischians.
Within each group there are animals moving on four and two limbs, giant individuals and very small ones, herbivores and predators.
In addition, the groups differ in the structure of the jaws and teeth, which is associated with a difference in nutrition.
Representatives of the lizards, for example, could not chew food, they swallowed it. Among the representatives of this species there were both herbivores and predators.
The ornithischian species consisted exclusively of herbivores. By the 21st century, researchers were able to give descriptions of more than 500 genera of prehistoric dinosaurs and 1000 species on all continents. The annual finds of paleontologists replenish the already existing list of dinosaurs with new finds.
giant size herbivorous dinosaurs, long neck and a huge strong tail, united in the order of sauropods, which is divided into smaller groups, for example - diplodocus. The theropods, which were bipedal predators, belong to the lizards, completely different from the diplodocus. This group includes allosaurs, tyrannosaurs, oviraltors and the first bird Archeopteryx.
Herbivorous ornithischian dinosaurs are divided into three main groups:
- ornithopods;
- horned dinosaurs;
- armored dinosaurs.
All the names of ancient lizards have Greek roots, like the term “dinosaurs”, which appeared in 1842 at the suggestion of the English scientist Richard Owen and translated from Greek means terrible lizards.
The largest were herbivorous reptiles from the group of diplodocus. Their length reached 30 meters, and the weight was generally fantastic - from 100 to 130 tons!
The most ferocious, terrible and dangerous predator prehistoric period was the tyrannosaurus. It differed not only in its gigantic frightening size, but also in the structure of the jaws, which did not cut, but tore, crushing and grinding the victim.

Behind long years publications of textbooks on biology and popular science books, a certain tradition has developed to depict dinosaurs. Ancient lizards are depicted as gigantic leathery creatures, with huge fangs - if it is a predator, and with a tiny head sitting high on a thin neck - if the lizard was a herbivore. The latest paleontological evidence proves that was not the case, and dinosaurs were literally soft and fluffy.

Appearance

Reconstructing the appearance of dinosaurs is a very difficult task due to the scarcity of surviving remains. Sometimes paleontologists manage to find the skeletons of ancient pangolins almost entirely and even with fragments of soft tissues. However, much more often, scientists come across individual bones or parts of them. In order to recreate the appearance of a person or a dinosaur, specialists need to determine how the muscles and tendons were attached to the bones, determine the approximate volume of soft tissues, place cartilage on the resulting "semi-finished product" and cover it all with skin. To do all these procedures, researchers first need to do a lot of calculations and decide on the most likely hypothesis. anatomical structure object.

If paleontologists are lucky enough to discover so far undiscovered dinosaur bone fragments, they can refine existing models of their appearance. Sometimes the amendments made do not change much big picture, but sometimes they force scientists to significantly reconsider their view of the appearance of ancient reptiles.

It was this kind of radical restructuring that occurred with the sauropod model. These giant herbivorous dinosaurs are considered the largest animals ever to have lived on land. The length of the smallest representatives of this group of ancient lizards was about 6 meters. The length of the record holders approached 60 meters. Scientists who discovered the first sauropod fossils suggested that their giant bodies rested on four thick legs, and a tiny head was located on a thin neck stretched upwards. Due to their size, sauropods could well eat leaves with tall trees like modern giraffes.

In order to ensure a normal blood supply to the head, giraffes, which are significantly inferior to sauropods in the length of the neck, have to resort to many tricks. They have acquired a very powerful heart, which creates a pressure three times higher than that of a human, and the blood of giraffes is three times thicker than that of Homo sapiens. Without these devices, the animals would immediately die from the pressure difference when the head is raised or lowered.

Sauropods have difficulty maintaining blood pressure there would be even more. According to recent calculations by researchers, the heart mass of pangolins should have been at least five percent of their body weight (for comparison, in humans this figure is about half a percent). Therefore, scientists came to the conclusion that the neck of the ancient giants was not directed upwards, but forward. That is how - horizontally elongated along the head-tail line - sauropods are depicted in most publications. However, more recently, work has appeared, the results of which may force paleontologists to return to the original point of view on the anatomy of sauropods.

T. rex with almost "correct" paws. In one of the recent works, it was proved that these lizards had three fingers on their forelimbs.

The authors of the new study proceeded from the assumption that colossal lizards were "arranged" in the same way as other animals moving on four limbs. In the course of evolution, they have acquired precisely those features that provide the best adaptation to the terrestrial lifestyle. Scientists have no reason to believe that sauropods have become an exception. Analyzing the structure of the skeleton a large number vertebrates, which included cats, rabbits, turtles and crocodiles, showed that their necks have a characteristic S-shaped curve that points upwards. The researchers concluded that sauropods most likely held their necks upright.

Comparative sizes of various sauropods and humans.

The new data has changed ideas not only about herbivorous pangolins. carnivorous dinosaurs also turned out to be not quite the same as it was commonly believed. Looking at pictures depicting huge bipedal theropods - a suborder of lizard dinosaurs, to which the famous Tyrannosaurus rex, - many paid attention to their forelimbs. Judging by these drawings, the tiny paws of predators dangled helplessly, palms down, somewhere at chest level.

A detailed analysis of the anatomy of the theropod forelimbs showed that, despite their unpresentable appearance, they were very strong. Scientists have put forward several hypotheses to explain the function of the forepaws. Most agreed that, most likely, with their help, predators held the caught prey for greater convenience of "processing" with their jaws. A recent paper has suggested that theropod's slightly absurd limbs were underdeveloped wings. Based on the analysis of fossilized footprints, scientists concluded that the palms of the front paws did not look down, but at each other.

The findings of the researchers move the beginning of the evolution of bipedal predators into birds. Until now, it was believed that the characteristic anatomical features began to appear in theropods at the end jurassic(slightly earlier than 145 million years ago). New data shift this event 45 million years ago, to the very beginning of the Jurassic.

What happened during the evolution of reptiles into birds can be observed every day. The appearance of winged dinosaurs is not so obvious to researchers. Long time paleontologists believed that the wings of pterosaurs were smooth and leathery and resembled the wings of modern bats. At the end of September 2009, a group of researchers presented evidence to the scientific community that this view was incorrect.

The authors new work studied the perfectly preserved remains of winged lizards found in Inner Mongolia. On the bones of reptiles Cretaceous there were even pieces of soft tissues. Their analysis showed that the skin of pterosaurs was covered with fine hairs, thickening closer to the surface of the lizard's body. At the moment, it is not clear whether they resembled the fur of mammals, or resembled the proto-feathers of some dinosaurs. What function the hairs performed is still unclear.

habits

The way of life of dinosaurs is even more difficult to restore than the appearance. Scientists judge the habitat, ways of feeding, reproduction and place in the ecosystem largely on the basis of the alleged appearance of pangolins. Accordingly, as certain ideas are clarified or rejected, the conclusions of researchers about the ecology of ancient pangolins also change.

So, quite recently, a group of Tokyo paleontologists stated that pterosaurs, considered a thunderstorm of the Mesozoic sky, flew very mediocrely. Scientists have analyzed the way of flight of several species of birds and determined the maximum possible body weight at which the bird is able to move efficiently in the air. According to the authors' calculations, pterosaurs were about six times heavier than the critical limit (the mass of these lizards could reach 250 kilograms).

On the other hand, pterosaurs could compensate for excess body weight due to a special respiratory system. A group of paleontologists from the US and the UK examined the bones of flying lizards using computed tomography and x-rays. Scientists have found characteristic cavities in them. In modern birds, air sacs are located in the cavities - organs where part of the inhaled air enters. The presence of air sacs allows oxygen-enriched air to pass through the lungs on both inhalation and exhalation.

Recent evidence suggests that another characteristic of dinosaurs has been misjudged. The fearsome predator T. rex may not have been so formidable at all and preferred to prey not on adult herbivorous giants, but on defenseless young. Scientists made such a conclusion based on the analysis of the bones of herbivorous pangolins discovered by paleontologists to date. The fossils found extremely rarely testified that the lizard was killed and "butchered" by a predator. But the half-digested bones of the young herbivorous dinosaurs and many of their embryos have been found.

Other predators of the late Cretaceous period also showed atypical behavior. Small, but nevertheless dangerous velociraptors liked to wait for their victims, hiding on the branches of trees. This conclusion was the result of work on modeling the biomechanics of the claws of ancient predators.

In addition to trees, the ancient lizards mastered another ecological niche- holes. Moreover, dinosaurs dug them themselves and experienced harsh conditions underground. Burrows have been found in Australia and North America. At the time of the dinosaurs, these territories were located at higher latitudes than they are now, since the continents in their modern form not yet formed. During cold periods, the temperature at night fell below zero, and the dinosaurs needed shelter. Some more data collected for last years, suggest that the ancient reptiles were much more frost-resistant than is commonly believed.

The inconsistencies between traditional ideas about dinosaurs and new evidence can be listed for a very long time. It can be mentioned that the sense of smell of dinosaurs was comparable to the scent of bloodhounds, that the eggs of some of the ancient giants were incubated by males, and the "teenager" dinosaurs gathered in gangs and independently obtained their own food.

As new facts are accumulated and verified, textbook authors will have to order new pictures and rewrite old texts. So the next generation of kids will have a completely different idea of ​​dinosaurs than we do. And what actually happened on Earth in the era of giant lizards, we, most likely, will never know at all.

Lizards is a conditional paleontological name for all vertebrates that are not fish, not a bird, and not a mammal. So, in general, lizards turn out to be naked frogs, and scaly lizards, dinosaurs, and armored turtles, and shaggy theromorphs (ancestors of mammals), and dozens of the most unexpected fossil groups of animals. This is how this tradition has developed in paleontology. The names of these animals usually include integral part words: "zaura" (lizard), or "zuhus" (crocodile), or even "gerpeton" (snake). The heyday of the lizards covers about 300 million years.

Carbon. The main variety of tetrapods was noticeable even in the water. Large and small, active predators and passively lying in wait for prey, flat-headed eaters of aquatic invertebrates, they occupied all coastal habitats, almost completely displacing lobe-finned and lungfish. Localities of this age are very rare, there are few of them in Europe and North America, and they have not yet been studied enough. Found mainly representatives of two, later widespread groups - batrachomorphs and anthracosauromorphs, known already from the Devonian, since Ichthyostega belongs to the first, and tulerpeton - to the second.

Permian. That's when the descendants of batrachomorphs and anthracosauromorphs, relatives of ichthyostega and tulerpeton, felt at ease. Hundreds of animal species from thousands of locations on all continents have been studied. Aquatic, primitive, perhaps breathing in addition to weak light gills, were replaced by fast, active, scaly, sometimes even armored ones. Labyrinthodonts-batrachomorphs are especially numerous, less armored anthracosaurs, and even fewer of their small terrestrial relatives. These lizards are without scales: through their bare, moist skin, wetted by special skin glands, one can breathe on land, although not for very long, in addition to still weak lungs. The paws of the ancient lizards were already well developed: you can not only walk, but also run. Small adjustments in the sense organs ("fitting" them to the air environment) - and you can rightfully be called an amphibian, that is, living in water and on land.

Later, batrachomorphs also created the same design, by the beginning of the Triassic, tailless (anura) appeared: toads and frogs. Quietly and calmly they lived to this day. Such a quiet life was not to the liking of the descendants of toothy anthracosaurs. True, some, such as parareptiles, remained at this level until the end of the Permian. But other, small ancestors of diapsid and theromorphic reptiles, already at the beginning of the Permian, began to go far on land in the excitement of hunting for insects. They went so far that there was no point in returning to the water. So, again I had to adapt: ​​the main thing is to protect your body and eggs from drying out. The eggs were covered with shells and special shells. Now the embryo developed as if in a small, own reservoir. On the other hand, it was no longer fish-like larvae with gills that came out of such eggs, but real small ... reptiles. The protection of the body of the reptiles was radically decided: some, diapsid reptiles, seemed to remember the ancient horny scales of their ancestors and covered themselves with its dense armor; others, theromorphic, acquired a dense coat with a thick, woolly awn, which reduced evaporation from the surface of the body. Both designs were successful - by the end of the period, both groups had spread widely around the world.

Triassic. Terrestrial localities of the beginning of the Triassic differ little from the Permian ones. At sea, conditions have changed; on land, changes have so far been late. Although some ancient groups have already begun to disappear. Batrachomorphic labyrinthodonts still lived quietly in the water, even made attempts to enter the sea, but the Permian diversity of parareptiles had already begun to wane, so that by the end of the Triassic, only turtles remained of them, which had completely changed to reptilian diapsidism. Large theromorphs disappeared, but small ones acquired many of the most useful structural features, which were very useful to them later, when their descendants became mammals, towards the end of the period. Only the diapsids not only did not give up, but, on the contrary, simply gained strength. With the end of the Middle Triassic, the "land Paleozoic" also ended - Frogs, turtles, lizards, primitive mammals, dinosaurs - this is a typical set of "land Mesozoic".

Yura. This is the era of the onset of shallow seas, warm and slightly saline. Of course, some of the lizards adapted to these conditions - they moved to live in the seas. Cephalopods - ammonites and belemnites, fish, ichthyosaurs, plesiosaurs - are the main population of water spaces. Unfortunately, we know less about land: the remains of terrestrial primitive mammals are very rare, the collection of remains of diapsids - lizards, crocodiles, dinosaurs - is richer. Among the latter, by the end of the period, real giants appear - eight-meter predatory megalosaurs, thirty-meter herbivorous sauropods, combed stegosaurs. By the end of the period, apparently, the first birds also appeared, although flying monsters dominated the air - toothed tailed rhamphorhynchus and toothless giant pterodactyls.

Chalk. The fauna and flora of the sea and land are becoming more and more modern. Still thrive cephalopods, ichthyosaurs, although the diversity of both begins to decline steadily. But now new water giants appear - relatives of monitor lizards mosasaurs. We find whole cemeteries of bones of giant bipedal and quadrupedal dinosaurs in the Cretaceous sandstones of many places on the Earth. True, there are very few supergiant sauropods, and by the middle of the Cretaceous, the diversity of bipedal herbivorous dinosaurs also decreases, only one group out of five in the Upper Cretaceous is flourishing. By the middle of the Cretaceous, stegosaurs disappear, and instead of them, horned ceratopsians quickly appear and disappear almost as quickly. Much less diverse than in the Jurassic are pterosaurs. But more and more remains of birds and mammals are found by paleontologists. They are still small, not very diverse.