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According to biologists at the University of Oslo, who analyzed the data on systematics and paleobiology, in Mesozoic time, the Earth was inhabited by 1936 species of dinosaurs. Although, their numbers may correlate between 1543 and 2468 species.

However, it is noted that it is difficult to accurately judge the number of dinosaurs who inhabited the Earth for 150 million years. Also, experts do not rule out that known to mankind bone fragments of animals, which belong to different geological stages, may belong to the same animals, but of different ages

Besides, it was previously reported that paleontologists in Brazil had discovered a previously unknown species of dinosaur. It was called the Teyujagua paradoxa. The dinosaur left a well-preserved skull. This means that the exact number of prehistoric reptiles is still unknown to science.

And anyway, of course, any calculations about the dinosaurs can be considered only approximate, but at any errors in the calculation of the figures are huge. So why was the Earth inhabited by so many prehistoric reptiles?

 Are many dinosaur species are there

1)Why Were There so Many Species of Dinosaurs?

One might legitimately ask, why are there so many different dinosaurs? This is where the work of paleontologists comes in. 

Paleontologists identify 3 main reasons that explain the diversity of the dinosaurs :

  • Habitat - Dinosaurs lived all over the world in a wide variety of habitats.
  • Nutrition habits - Dinosaurs had very varied diets, which allowed them to develop more serenely and to be less in competition with each other. 
  • Evolution - These two first points have allowed different dinosaur species to evolve differently over time in order to better adapt to their own habitats and habits.


Let's take a closer look :


A)Wide Variety of Habitats

There were different species of dinosaurs in different parts of the planet. In Mongolia, the river delta was inhabited by Tyrannosaurs, Gadrosaurs, and Ornithomimosaurs. And just a few tens of kilometers from them, on the territory of the present Gobi Desert, settled small Ceratops and Oviraptors. Similarly, a variety of dinosaur species inhabited other continents.
The difference in species between continents was even greater. In the Late Cretaceous, Tyrannosaurs, Gadrosaurs, and Ceratops dominated North America and Asia. Meanwhile, in Africa and South America, which separated tens of millions of years ago, the leading species were completely different: Abelisaurs were the highest predators there, while herbivores were long-necked Titanosaurs.


B)Different Dietary Habits

Dinosaurs were highly specialized animals. Different species occupied different niches and therefore could coexist without competition. For example, in western North America, the giant T.Rex predator successfully shared its habitat with small carnivorous Dromaeosaurs. Huge long-necked dromaeosaurs fed on highly growing leaves next to horny Ceratopes, which fed on flowers and ferns. There were also very small herbivorous Pachycephalosaurs and Ornithomimides, as well as fish-eating and even spider-eating dinosaurs.

And even within these niches, there was a narrower specialization. T-Rex was huge and had giant jaws. But because of the weak, short front limbs, he was best suited to hunting a slow, though very formidable triceratops. And T-Rex's relative Nanotyrannus was smaller than he was, but he had long legs and knew how to chase fleeing prey. Similar to herbivores, some eat leaves in the treetops, while others eat bushes at ground level. 
And this narrow specialization means that 25 different dinosaur species could live in the same area without competing with each other.


C)Rapid Evolution

New species of dinosaurs appeared at an impressive rate. Radiological dating made it possible to determine the age of fossilized dinosaur residues and thus to determine how long dinosaur species existed. Scientists believe that one species replaced the other quite quickly (about a million years for each species - a small period by geological standards). Dinosaurs have evolved rapidly due to changes in the planet's climate, the movement of seas and continents, and the evolution of other dinosaur species. And if they didn't, they were extinct. 

And yet, is it possible somehow to identify the main most numerous species of these ancient creatures?


2)What are the main groups of dinosaurs?

All dinosaurs are divided into two main groups - Ornithischia and Saurischia dinosaurs. They were named after the shape of pelvic bones.

These 2 groups are in turn divided into subgroups, and they are divided into families and subfamilies. Let's take a short look at them.

 The saurichians dinosaur

A)The Saurischians

Saurischians are the group of dinosaurs with a reptile pelvis, i.e. a three-branch pelvis. 

This group is divided into two major subgroups. Many of the most popular dinosaurs come from this group.  


1. Theropoda: They are bipedal predatory dinosaurs with relatively large heads and mouths full of sharp teeth. All theropods were predators and had small, in comparison with the hind powerful, front extremities, well suited for capturing prey and ending with sharp, powerful claws.

The most popular representatives of this group are:


2. Sauropodomorpha:They are vegetable-eating dinosaurs whose characteristic feature was a relatively small head located on a long neck. The massive barrel-shaped body was held on four large, pillar-like legs. Sauropodomorphs differed among themselves by some features of the body structure, such as the size or number of cervical vertebrae. The neck was shorter than that of the Proseuropod. They are divided into a Zauropod and a Prozauropod.

The most popular representatives of this group are:

   a) Sauropod Family

  • Diplodocus
  • Apatosaurus
  • Brontosaurus
  • Brachiosaurus

   b) Prosauropod family: 

  • Plateosaurus
  • Bagualosaurus
  • Unaysauridae          

the Ornithischians 

B)The Ornithischians

Ornithischians are the group of dinosaurs witha bird pelvisi.e. a four-branch pelvis. 

This group is divided into five subgroups: Ornithopoda, Ankylosauridae, Stegosauria, Ceratopsidae, and Pachycephalosauria.

All Ornithischia dinosaurs were herbivores. Each group of dinosaurs had individual distinctive features. 


1. Ornithopoda:They mainly had powerful hind limbs but could lean on the front limbs while walking. The head of these dinosaurs had a slightly elongated shape. All ornithopods were herbivorous dinosaurs.

The most popular representatives of this group are:

  • Iguanodons (widespread in the early Cretaceous Period)
  • Hypsilophodon

2. Ankylosauridae: They had a bone coating protecting the dinosaur back and neck. There was a large and heavy mace on its tail with which the Ankylosaurus effectively defended itself against predators. These dinosaurs moved on four strong legs and looked like a tank. 

The most popular representatives of this group are: 

  • Ankylosaurus.
  • Gobisaurus


3. Stegosauria: They were different in size. But they all had characteristic diamond-shaped plates or spikes located along the whole body from back to tail. All Stegosaurs had four long spikes on their tails, which were excellent weapons against predatory dinosaurs.

The most popular representatives of this group are: 

  • Stegosaurus.
  • Alcovasaurus


4. Ceratopsidae:  On their heads, they wore horns or horns directed forward like modern rhinos. The bone collar protected the head and neck of the dinosaur. All Ceratops had a powerful body and moved on four powerful paws.

The most popular representatives of this group are: 

  • Triceratops
  • Styracosaurus


    5. Pachycephalosauria:They walked on two legs and had a powerful dome-shaped bone node in the area of the shadow. At the largest thickness of the parietal part of the skull reached 20-25 centimeters.

    The most popular representatives of this group are: 

    • Pachycephalosaurus
    • Alaskacephale


    We'll never know exactly how many dinosaurs there were on this planet. Not all of them have survived in fossils, so probably hundreds of thousands of species are lost to us forever. But still, in recent years, new dinosaur species have been found more and more often, so thousands and thousands more are waiting to be discovered. Who knows, maybe in the future, new dinosaur species will be added to this classification.