According to modern paleontologists, the giant ancient reptiles began to master the water element at the end of the Permian period of their life on Earth. Scientists claim that the ancient reptiles throughout their lives always returned to the water. The reason for this is the abundance of underwater food and, of course, safety.
In the seas and oceans
It is curious that life in the seas and oceans did not at all require any fundamental reorganization of the organism from the ancient lizards: one only needs to recall modern reptiles that live in water, but have a completely land appearance. For example, these are crocodiles or marine iguanas.
It is worth noting that the movement and nutrition of dinosaurs in water is energy costs, accounting for only a quarter of all the costs necessary for their movement and nutrition directly on land! The so-called primitive dinosaurs, a dead-end branch in evolution, returned especially easily to water. But this is a completely different story.
The first floating dinosaurs - who are they?
Scientists believe that the first true aquatic dinosaur species were Perm Mesosaurs, representing a subclass of anapsids. Already after them, representatives of the so-called primitive diapsids returned to the water: the Tangosaurs, Hovasaurus and Claudiosaurs.
All of them belonged to the eosuchian order and reached a length of only 50 cm. Only in the middle of the Triassic period did these floating dinosaurs “grow” to two meters in length, finally turning into serious and even dangerous reptiles.
Outwardly, they resembled today's newts from the amphibian class: aquatic eosuchies had a long tail flattened laterally and a crest extending along the back through the entire body. In the Triassic period on Earth there were no more than 5 groups of aquatic reptiles. One of them we just examined is the aquatic eosuchia. Consider in detail the other types of floating dinosaurs.
Placodonts
Outwardly, these reptiles resembled small long-tailed seals. Their length did not exceed 1.5 m. The body of the placodonts had a streamlined and spindle-shaped shape. The head is small, the legs are short. The swimming methods of dinosaurs belonging to the placodont group did not differ in particular variety: reptiles simply stretched their awkward short legs along the body and swam like small torpedoes.
As mentioned above, the whole truth about placodont dinosaurs, as well as about many other water reptiles, is shrouded in darkness and mystery. Scientists are inclined to believe that these are the descendants of some ancient anapsids. Nevertheless, the age of the placodonts was short - these creatures were born at the beginning of the Triassic, but by the end of it they had completely died out.
Notosaurs
This is another floating dinosaur that lived in the Triassic. Their sizes reached 4 m in length, but the vast majority of them were still noticeably smaller. Predatory reptiles had a streamlined body, a short tail, a rather flexible neck, equal to the length of their body.
They had a small head with a mouth armed with sharp teeth. These creatures moved in water with the help of the uniform movements of the tail, creating a motive force, as well as through their webbed feet.
If there was a need for notosaurs, they easily climbed ashore and basked in the sun. Scientists are sure that predators were ancient species of fish. It is curious that in the second half of the Triassic period these creatures gave rise to a separate branch of the now famous aquatic predators - plesiosaurs. The notosaurs themselves became extinct by the end of the Triassic.
Tallatosaurus
Representatives of this group externally resembled the above notosaurs, only the neck was shorter and the head was larger. The swimming methods of dinosaurs of this group cannot be called unique: they did not use their paws to row at all, but simply stretched them along the body, like placodonts.
Scientists are inclined to believe that these creatures evolved from some ancient and primitive anapsids, even more ancient than the previously mentioned water eosuchia. They died out by the end of the Triassic, as did the notosaurs. No descendants were left behind.
Ichthyosaurs
This is the last group represented by the most famous floating dinosaurs in the world - ichthyosaurs. Ichthyosaurs better than all other lizards were adapted to life and habitat in the seas and oceans. It is known that these predators are descendants of diapsids, and it is not known which ones. Ichthyosaurs appeared in the Permian period, although the most ancient remains of these reptiles date from the Lower Triassic period.
Outwardly, ichthyosaurs completely repeated the shape of today's fish. Their triangular head with jaws extended forward resembled the head of dolphins. The trunk flattened from the sides, the vertical tail lobe and paws, which turned into fins, made them unlike all their aquatic predecessors.
