How dinosaurs appeared on earth How dinosaurs appeared on earth When Dinosaurs Lived How Dinosaurs Used to Live

The word "dinosaur", which translates as "terrible lizard", appeared in 1842, when humanity was just trying to figure out what kind of bones these are found during excavations. It was then that the science of paleontology was born. The history of dinosaurs has been rewritten many times since then, and this moment there are many versions about their origin, formation and extinction. Consider the most common and relatively official version.

The origin of the dinosaurs

Attempts to explain plain language The history of dinosaurs in a film or cartoon has been made repeatedly, but the events that preceded their appearance on our planet were practically not covered anywhere. As you know, the ancestors of these creatures are reptiles and birds. In particular, the crocodiles that exist at the moment have the most similar features to the ancient monsters. About 300 million years ago, when lizards already existed in the form we are used to, there was a serious climate change. Rainforests were largely destroyed, and the remnants of life huddled in the remaining small enclaves. This gave the first impetus to a huge variety of species, as each population developed independently of each other and tried to adapt to the conditions in which it existed. And they were very different different regions. This is how the ancestors of dinosaurs appeared, called archosaurs by scientists.

First views

The history of dinosaurs, at least in the form in which they are presented modern man, began about 200-245 million years ago. There is practically no exact data on the features and differences of these creatures compared to later samples, but something can be said for sure:

• They were bipedal (dinosaurs with four legs appeared a little later, although the opposite situation would have looked logical).
• The creatures were quite large, mostly their growth reached 2-4 meters.
• All of them were cold-blooded. Because of this, the need for food, despite its impressive size, was not too great.
• On the early stages development, most likely, there were no flying species of these pangolins.

In general, humanity knows very little about this period. Most of the information is guesswork and theories based on various findings and circumstantial evidence. So things could be completely different.

The Last Dinosaurs

The size of the "terrible lizards" gradually increased, and this continued until about the end of the Jurassic period (this was about 145 million years ago). In the middle of their life cycle, dinosaurs reached enormous sizes (up to 12 meters in height and 1 ton of net weight). During the "reign" of these monsters, no other species simply could not even conditionally claim dominance on the planet. Even later, in the Cretaceous period (65 million years ago), the creatures began to shrink. According to some reports, they developed the beginnings of feathers, and even warm-blooded species arose. Judging by the available information, the number of predators has significantly decreased, and, accordingly, the number of herbivores has increased. As a result, rare hunters have become truly real "killing machines". They moved quickly, could cope with most opponents, had no shortage of food and were rightly considered at that time the pinnacle of evolution.

mass extinction

The situation with the disappearance of this type of living creatures is well shown in the cartoon "The History of Dinosaurs". Of course, there information is more focused on children, but actively active volcanoes, drought, lack of food and other similar problems could really cause the complete extinction of the prehistoric rulers of the planet. According to the official version, it all started with a huge meteorite that fell somewhere in the region of present-day Mexico. When hitting the atmosphere rose a large number of dust, which sharply lowered the temperature on the surface (a similar situation is called " nuclear winter” and can become a reality if countries try to solve their problems through nuclear weapons). Along the way, the impact on the Earth activated dormant volcanoes. As a result, the simultaneous impact of several factors at once led to the fact that dinosaurs simply did not have time to adapt and during short period almost completely died out. Most likely, individual individuals remained, but they could not survive in a new world in which other dominant species appeared. Many people think that this particular dinosaur story is for children. Allegedly, in fact, everything was completely different. Unfortunately, in the future, scientists disagree in their opinions, and no one can yet give a clear theory of how everything really happened.

Many intriguing and mysterious things are shown in documentaries"History of Dinosaurs" from Popular Science Channels. True, they cannot be called documentary, since there are no documents, but everything there is reconstructed very competently. Nevertheless, every year more and more discoveries are made that radically change the idea of ​​dinosaurs as such. Let's see what Interesting Facts opens up to us modern history dinosaurs.

• Despite the fact that, as it was believed, dinosaurs were almost a mistake of nature (too small brain, big weight, severely restricted diets, and so on), they managed to dominate the planet for over 130 million years. The history of man as such, if we take our more or less reasonable ancestors, is at best 100,000 years old. So it is not a fact that in the distant future some new species will not be considered a mistake of a modern person.
• Tyrannosaurus, known in many films and literature as the most terrible and huge dinosaur, in fact, was not one. There were even more creatures, however, unlike this predator, they were still not hunters.
• The history of dinosaurs is still silent about why a tyrannosaurus needs its small hands at all. Judging by the structure of the skeleton, he simply could not reach them anywhere. Even more mysterious is the fact that these hands had very well developed muscles.
• Stegosaurus plates were used primarily not to protect against predators, but to remove heat. That is, they played the role of a natural radiator, in one case cooling huge dinosaur, and in another, helping him to accumulate heat more efficiently, which is extremely important for any cold-blooded creature.

Results

The history of dinosaurs is gradually overgrown with new data, some of which contradict each other or do not fit into existing theories. For example, it is believed that dinosaurs and humans could not have existed in the same period of history. Although there are very interesting finds, stones, on which ancient people quite reliably depicted the interaction of a person and a “terrible lizard”. As it was in reality, no one can say yet. We are unable to fully understand even own history what can we say about what happened long before the appearance of man as such.

What kid doesn't love dinosaurs? That's what I loved.

I even had huge collection toys. My special childhood pride was a big tyrannosaurus rex and a battery-operated triceratops - they walked and growled. I also had enough books and encyclopedias about dinosaurs. And my drawing of a Tyrannosaurus rex was even hung by a pediatric dentist in her office - among other masterpieces of her little patients.

In general, I have the warmest relationship with dinosaurs.

Who are dinosaurs

We all know dinosaurs, but who are they on the tree of evolution?

Dinosaurs- This reptiles(they are reptiles), as well as the well-known snakes, lizards, turtles, etc.

But dinosaurs are not the first reptiles on Earth.

primitive reptiles, cotylosaurs, already existed in carboniferous period(its beginning is approximately 358.9 million years ago). In the future, the number of reptile species increased, they were more and more divided into various groups.

The apogee of the evolution of reptiles was the appearance of dinosaurs.

They were so common that their remains can be found on all continents. The variety of types and forms is impressive.

To be honest, I love everything theropods are bipedal and usually carnivorous dinosaurs. If I were their contemporary, I would like them much less (but they would like me exclusively in the gastronomic sense). But they are really very beautiful - such predatory grace!

My favorites are Allosaurus and Deinonychus.

contemporaries of dinosaurs- This crocodiles who lived then and live now. Over the past millions of years, they have not changed much. Why do we need evolution if your species is already living wonderfully? So the crocodiles decided that she did not need them.

when they lived

A very, very long time ago. There weren't even people back then. The Flintstones' pet dinosaurs are nothing more than a figment of the imagination.

The evolution of reptiles lasted many millions of years, its heyday fell on the era giant lizards - dinosaurs. And this the era was called the Mesozoic.

Mesozoic includes three periods:

• Triassic;
• Jurassic;
• chalky.

Total mesozoic era lasted about 186 million years. Dinosaurs existed on the planet longer than humans!

Temporary boundaries mesozoic: 251.902 ± 0.024 mya - 66.0 mya

The origin of dinosaurs has been one of the most poignant mysteries and discussions of the last century. But even now, extremely little is known about these lizards. What were they like? Can the dinosaur be considered the "king of nature" and the pinnacle of the food chain your period?

These and many other questions have not yet been answered. Even those fragments of information that archaeologists and paleontologists managed to collect are based more on the analysis of fossils and theories built around the principles of life of similar organisms.

Many species of dinosaurs are still only superficially studied, and therefore there is no need to talk about a sufficient knowledge base on this issue.

Basic classification of dinosaurs

The difference between dinosaur species is dictated by habitat, food preferences, dietary habits, and even class.

Some names come directly from the names of the discoverers, as well as the territories where the skeleton of one or another pangolin was first found.

The type of dinosaur also varied significantly depending on which predator dominated the region. Yes, to

for example, huge diplodocus were perfectly protected from small aggressors, for example, deinocheirs, but not only hunted for the young of this subspecies of herbivores, it literally threatened their population.

In general, dinosaurs can be divided into 4 classes:

• Predators.
• Herbivores.
• Flying.
• Water.

However, some dinosaurs managed to combine several classes in their specificity.

Predators

The class of predators includes several subspecies, which can be conditionally grouped into two categories: large and flocking.

The class of the first, for example, can be attributed to "Tyrex", in other words, a tyrannosaurus rex. He was one of the most famous predators its period, which is about 65 million years ago.

This dinosaur, like its fellows, is characterized by a solitary lifestyle with hunting mainly for large game. With a length of fangs of 15-19 centimeters, it was not a problem for this lizard to bite through even the strong shell of a stegosaurus or to come together in a fight with a triceratops.

Its name even contains a direct reference to the reputation of the lizard - namely, the prefix "tee", whose entomology is close to "terror", which translates as "horror".

Allosaurus, Dilaphosaurus, Carnotaurus and Megalosaurus should also be attributed to the same kind of dinosaurs.

The latter species are quite characteristic, but the complete skeleton of this lizard has never been found.

pack predators distinguished by considerable intelligence and hunted mainly young growth of large herbivorous dinosaurs and sick loners.

Could not only coordinate their actions within the pack, they were in contact with

other representatives through sound effects. If the brain of an average stegosaurus reached the size walnut, then in Velociraptor it was already the size of a large orange.

Distinctive feature This type of dinosaur is a large claw on the first toe of the hind paw, through which hunting took place.

Velociraptor jumped on the back of its prey, after which it tried to break the spine or inflict wounds leading to blood loss. This species of dinosaurs is characterized by hunting in a pack, the type of which is similar to the actions of wolves.

Herbivores

The class "herbivores" has several subspecies. Most often they are called according to the names of several of the most well-known representatives(Triceratops, Stegosaurus and Diplodocus).

At one time, the last of those mentioned was for the entire period of the existence of lizards. Its length from the nose to the tip of the tail reached 30 meters.

Ultrasaurus was supposed to be the new record holder, but, as in the case of Megalosaurus, a complete lizard skeleton has not been found. This species is characterized by huge sizes, even the “smaller” of them, namely the Apatosaurus reached a record 22 meters.

A dinosaur called Triceratops was not in danger of a head-on fight. Like the modern rhinoceros, this dinosaur crushed the enemy with its horns, although they were present in the amount of three pieces, and the neck of the lizard was covered by a bone “collar”, which also served to regulate heat transfer.

Stegosaurs and brontosaurs preferred defense to attack. Such dinosaurs just had to stand on their feet, huddle together and patiently wait out the attack. Their backs are tightly protected by a horny shell.

The stegosaurus also had spikes at the tip of its tail, with which the lizard skillfully defended itself from small aggressors.

One of the heaviest dinosaurs, namely the brontosaurus, had a heavy bone mace at the end of the tail, which could easily break through the skull, for example, of a velociraptor.

Aquatic

Aquatic dinosaurs are almost completely represented by the predator class. The largest of them, namely the plesiosaur, according to a number of scientists, may well be the same. The length of his neck reached 11-15 meters.

Mosasaurus and Ichthyosaurus are named as the ancestors of modern dolphins.

Pliosaurus, also known as "predator x", was the most aggressive. This dinosaur is characterized by attacks, including on its own relatives. It is likely that killer whales are the heirs of the pliosaurus. Most of these lizards became extinct after average temperature water began to fall as a result of the offensive ice age.

flying

Some flying dinosaurs later evolved into birds, others remained a subclass of their own, but they posed a serious threat to their habitat and deserve a mention.

He hunted insects (the size of which reached 2 meters during the existence of the lizard) and he himself was far from small. It was in his skeleton that the remains and traces of the feather cover were found, after which the origin of modern birds from this subspecies was proved.

The second subclass, represented by pterodactyl, had a wooly coat and huge leathery wings. Dinosaurs of this species are characterized by a diet of fish, fruits and insects.

Each type of dinosaur was distinguished by its own specifics and features. So compressed characteristic unable to give full assessment this, however, is sufficient for the primary. At one time, dinosaurs were a huge force, but later lost the battle to nature and even mammals, losing the championship once and for all.

Hello! Today we will talk about the animals that reigned on Earth in the past. Now we will look at what are dinosaurs? Consider predators and herbivores, as well as find out what parents were dinosaurs and some theories of their extinction.

Having reigned on Earth for 160 million years, dinosaurs disappeared from the face of the planet about 65 million years ago. Where did these giant reptiles come from? What did they really look like and why did they die out?

Dinosaur in Greek means a terrible or terrible lizard. About dinosaurs scientific knowledge are formed mainly on the basis of the study of fossils that turned into stone fossil remains of animals or plants.

Modern paleontologists have a fairly clear picture of how the dinosaurs originated, their lifestyle, anatomy, habitat, species diversity, distribution and reproduction in prehistoric form.

Specialists in small flaws in fossilized bones can judge the muscular apparatus of dinosaurs, and they judge what these ancient lizards were sick with by the appearance of individual bones.

If you carefully study the skull of a dinosaur that died 200 million years ago, this will give an idea of ​​the dinosaur nutrition structure and the size of the brain.

Fossil eggs tell about baby dinosaurs. But such hypotheses as, for example, whether ancient reptiles had hair, and what color their skin was, are much more difficult to confirm.

Age of dinosaurs.

From its origin, approximately 4,500 million years ago, the entire history of the Earth is divided into eras (in more detail about geological history Earth can). Most Mesozoic or middle era covers the era of the dinosaurs.

The Mesozoic era, in turn, consists of three periods - the Triassic (225 - 185 million years ago), the Jurassic (185 - 140 million years ago) and the Cretaceous (140 - 70 million years ago).

Even before the advent of dinosaurs, reptiles existed on Earth. Many new species arose at the beginning Triassic period. These are, for example, swift-footed kynodonts (“dog-toothed”) that hunted clumsy herds of herbivores.

Like most modern lizards, the paws of ancient reptiles were located on the sides of the body. They were replaced by archosaurs ("dominant lizards").

From all others, one group of these reptiles differed in body structure - their limbs were vertically under the body.

That successful skeletal construction that we find in their descendant of dinosaurs probably originates from here.

The first real dinosaurs roamed the Earth by the end of the Triassic period. However, the heyday of their era fell on the Cretaceous period, when the number and diversity of species of these reptiles reached their apogee.

Scientists today have over 1000 species of dinosaurs, which are clearly divided into two groups - carnivorous and herbivorous pangolins.

Sauropods.

Dinosaurs ranged in size from gigantic sauropods to baby compsognathus predators, which were no larger than a rooster.

They were herbivorous giants with a huge body, a small head and long neck, like a giraffe, which allowed them to reach the tops of the trees to feast on the most delicious leaves.

They cut leaves from trees with their teeth, similar to nails, and chewed them into a homogeneous mass with blunt molars. Diplodocus ("double lizard") reached a length of 26 meters and weighed 11 tons.

Brachiosaurus was 28 meters long, 13 meters high and weighed 100 tons - the same as 16 African elephants. They ate only plants and in order to survive, they had to eat about a ton of leaves a day.

In the skeletons of some fossil sauropods, in the place where the stomach should have been, huge stones were found. These ingested stones apparently helped to grind up leaves and rough twigs in the process of digestion.

Self-defense.

Many in search of food herbivorous dinosaurs moved in groups. In order to more successfully fight off predators, they often huddled in large herds.

Triceratops did this to protect their young. Adult individuals, in the event of an attack, surrounded the young in much the same way as elephants do now.

However, many "peaceful" dinosaurs were also decently armed. Like a rhinoceros, Triceratops rushed into battle, and pierced with two huge sharp horns, which were located in the frontal part of the snout, its enemy.

Pinacosaurs stunned their opponents with blows from a heavy bone outgrowth at the tip of their tail. Other herbivorous lizards like the Stegosaurus were protected by rows of large bony plates along their backs and sharp tail spikes.

Tyrannosaurus.

Rip the victim to pieces carnivorous dinosaurs allowed sharp teeth bent inward, and kept it in place by sharp and long claws.

The largest of the carnivorous dinosaurs was the tyrannosaurus ("titan lizard"), it weighed 8 tons and was 12 meters tall.

His curved teeth reached 16 cm in length - almost the size of a human palm (depending on which one, of course).

Dinosaurs, despite their size, could move very quickly. Long-legged "ostrich" dinosaurs could run at speeds up to 50 km / h.

Of course, such heavyweight dinosaurs as, for example, the 35-ton Apatosaurus, probably moved at a speed modern elephant, and a 100-ton clumsy brachiosaurus could hardly move at a speed of more than 4 km / h (like walking a person).

Sauropods needed strong legs to move. A springy step "from heel to toes", like a human, required a very large expenditure of energy, and a large dinosaur would not have gone far with such a step.

Sauropods (i.e. giant "lizards") ran rather than walked. To support a massive torso, their limbs had to walk the entire plane of the sole.

And therefore, between the “heel” and the fingers, they had a thick keratinized roller, like a modern elephant on the sole.

Caring parents.

For a long time it was believed that dinosaurs built nests and laid eggs. But how the young were reared remained a mystery; and it was only in 1978 that the curtain was opened when a nest was found with newborn babies and eggshells in American state Montana.

The length of the eggs did not exceed 20 cm, and some cubs were up to 1 meter long. These dinosaurs were very large for newborns, which means that they still remained in the nests. long time after birth.

Scientists, based on these data, came to the following conclusion: parents took care of the kids until they grew up enough and could take care of themselves.

Many of the cubs found in Montana had worn teeth. This means that their parents fed them in the nest, as birds do now.

Some experts had doubts that the giant parents were able to feed offspring without causing harm.

But after all, the largest reptile of our time, the alligator, also nurses its offspring and does it with the greatest care.

There is growing evidence that some large species Dinosaurs, like mammals, were viviparous.

Since many dinosaurs were constantly on the move to escape from enemies and in search of food, they did not have time to lay their eggs, and then wait weeks, or even months, for the appearance and maturation of small dinosaurs.

And besides, the most large egg dinosaur that was found does not exceed 30 cm in length. The baby that hatched from it was not much bigger, and it would have to grow very fast to reach the size of an adult dinosaur.

And so, some scientists put forward the theory that largest dinosaurs were born alive - and quite large.

First fossils.

For hundreds of years, people have met fossilized bones of dinosaurs, but few of them could have guessed what it was. Some even considered them to be the bones of giant people!

And only in the 1920s, people began to realize that in front of them were the remains of extinct giant reptiles.

Gideon Mantell in 1822 found some huge teeth in a quarry in Sussex, in the south of England.

He, after noting the similarity of these teeth with the teeth of the South American iguana lizard, guessed that the teeth found belonged to a reptile, and came up with the name iguanodon for it, that is, "iguano-toothed."

Dinosaur fossils are found in almost every corner of the world. They are found on all continents, including Antarctica.

Teeth and bones come across most often, because these elements of the skeleton are much less susceptible to decomposition than soft tissues (innards, skin).

Footprints take second place. They are in many cases found on the trails that dinosaurs made in soft ground.

Who hunted whom, as well as the places of settlement of lizards can be determined by the tracks. Fossil footprints are called residual fossils because they do not, in fact, belong to the animal itself.

Coprolites (fossilized dinosaur excrement) are dissected and examined along with intestinal contents and stomach stones to find out what ancient pangolins ate.

Dinosaur skin prints have also been found. They can tell a lot about the plastic armor of their masters.

No one knows what color the dinosaurs were. Their skin, not having time to petrify, decomposes too quickly.

Predatory lizards, according to some scientists, had a protective coloration that allowed them to blend in with the terrain and sneak up on prey unnoticed.

Other reptiles, herbivores for example, were very large and could not be afraid of predators, and they may have had bright coloring in order to attract the opposite sex.

Sudden death.

Dinosaurs became extinct about 65 million years ago, at the end Cretaceous. There are several theories on this subject, but paleontologists still cannot give a convincing explanation for the reason for their death.

According to one theory, not far from the Earth, a star explosion occurred, which covered the planet with deadly radiation.

At one time, scientists put forward such a theory that, being cold-blooded animals that are not able to regulate their own body temperature, they simply died out from the cold snap that swept the entire planet at the end of the Cretaceous period.

But now, when evidence has appeared that some species of lizards were warm-blooded, this theory no longer explains the mystery of their death.

In Mexico, on the Yucatan Peninsula, traces of a giant crater were discovered. This suggests that a huge meteorite collided with the Earth, and this collision was accompanied by a powerful explosion.

Huge clouds of dust rose into the atmosphere (more about the atmosphere), which hid the sun for several months, and this led to the destruction of almost all life on Earth.

Winters got colder or summer heat intensified, benefited from it small mammals that are capable of hibernation. This is another theory of dinosaur extinction, by the way, it is the most popular and widespread.

But true reason The death of dinosaurs, we, apparently, will never know.

Well, that's all about these terrible lizards. I hope this article has helped you find out who dinosaurs are and who they really were. But still there is a lot of unknown in this area, and I think that scientists will gradually find answers to these riddles...

In the scientific world, they came to a consensus that living organisms appeared on our planet 4.5 billion years ago. For the first half a billion years of its existence, the living potential of the Earth was very primitive - the simplest, primitive organisms dominated the world "broth", by which it was impossible to determine whether it was an animal or a plant.

But already 4, billion years ago, evolutionary progress was outlined, and life forms began to become more complex and increase in number. And already by the Cambrian period, i.e., about 550 million years ago, the oceans were already inhabited by worms, sponges, mollusks, different kinds coelenterates as representatives of the fauna, and on the other hand - algae, representatives of the flora. In the scientific world, this period is called the "Cambrian Super Explosion". This evolutionary explosion gave a further powerful impetus to the development of species. Firstly, there was a specific differentiation between the plant and animal kingdoms, and secondly, evolution accelerated significantly, and after several million years the first vertebrate organisms appeared in the ancient ocean, followed by the most important living creature, the lobe-finned fish.

It is the lobe-finned fish that is the transitional chain between marine and land animals. She was found in the 19th century near Madagascar, where she lived peacefully and lives in local waters. Her skeletons have been found before, but a living specimen convincingly proved that the exit of animals from the sea to land was another of the most important points in the history of evolution on Earth. The lobe-finned fish tried to land on land with the help of its modified fins, but it could not stay out of the water for a long time, but gradually everything changed, and for about 100 million years this transition took place.

Scientists believe that the first vertebrate land animals appeared on the planet in the Devonian period, because by this time they could feed exclusively on land. They are also called stegocephalians or shell-headed amphibians.

The next milestone in the development of species is carboniferous period. At this time, the first reptiles appeared on Earth. Scientists named them cotylosaurs. Cotylosaurs began to successfully breed and destroy stegocephalians. Need to say. that cotilosaurs were the progenitors of all species and subspecies of reptiles on our planet. But for some reasons unknown to science, by the middle of the Permian period, there was no longer a single cotylosaurus on Earth. They died out, and in their place came a more complex species - therapsids. They are also called animal-like vertebrates.

Therapsids were divided into carnivores and herbivores. They were a megapopulation until the early Triassic period. But here comes Permian and archosaurs became the “main” on Earth - the most ancient dinosaurs, they are also called thecodonts.

The development of reptiles on the planet proceeded at an accelerated pace and is very productive. Just the Mesozoic era became a paradise for all their species. The Mesozoic includes 3 consecutive periods.

Triassic

Jurassic period

Cretaceous

The longest was mesozoic period- it lasted about 70 million years. In these times, the reptiles had no rivals, therefore, having such a paradise life without shocks and a huge amount of food, the animals produced a large number of species. Some of them returned to sea ​​depths and, by the way, very quickly adapted to life in the water. So there were plesiosaurs, ichthyosaurs and others aquatic dinosaurs. Evolution presented a revolutionary view in the Mesozoic - flying lizards. They were called pterosaurs.

The Triassic period gave the so-called centenarians - land turtles and crocodiles, they already existed at the end of the Triassic and feel great now. What fantastic adaptability must be possessed in order to survive thousands of other species that could not withstand catastrophes and drastic changes climate.

Dinosaurs also appeared on Earth along with turtles and crocodiles at the end of the Triassic period. Ancient lizards were Herrerasaurus and Eoraptor.

The Mesozoic began 235 million years ago and lasted for about 160 million years.

Thecodonts are the animals from which the dinosaurs evolved. More precisely, they are also called ornithosuchia. These creatures were nimble, slender and ran very fast. Ancient lizards were divided into two categories - lizard and ornithischian. The pelvic part of some was approximately the same as that of modern reptiles, and in the second category, the pelvis resembled that of birds. In addition, ornithischians had an auxiliary bone that covered their jaws like a bird's beak. There was another mixed category of dinosaurs. These are segnosaurs. Their constitution bore signs of both lizard and ornithischian groups of their fellow tribesmen. And some features of the structure of segnosaurs were inherent only to their species. According to the remains found, paleontologists concluded that in jurassic nevertheless alpha dinosaurs were lizards. Initially, this species was carnivorous. They quickly moved on powerful hind limbs, and deftly grabbed the prey with their front ones. But as a result of further evolution, herbivorous relatives descended from them. The diet has changed dramatically, not to mention the amount of vegetation consumed. The weight and size of these creatures began to go off scale. Such a huge weight was difficult to hold, so they began to use all four limbs for movement. Scientists called this species sauropods or lizard-footed dinosaurs because of the structural features of their limbs. This group is represented by 40 genera. Those dinosaurs that continued to walk on 2 legs were called theropods or animal-footed dinosaurs. Theropods were predators and there were 150 genera.