paleontologist found that the tail sauropterygia, which include the plesiosaurs, were flattened horizontally. These reptiles moved mainly by two pairs of powerful fins and vertical swings of the tail. Article published in the journal Biology Bulletin.
Various groups of modern and extinct reptiles secondarily adapted to an aquatic lifestyle. They used several styles of swimming and formed various locomotor apparatuses, which can be studied on live representatives, or to recover the remains of fossil species.
PERVICHNAYA vertebrates (jawless fish) moving with wavelike oscillations of the body in the horizontal plane, and the main role in the locomotion belongs to tail. Most sea snakes, extinct and living, also use a horizontal movement of the body. These include, for example, crocodiles, lizards, and ichthyosaurs. They have long, strong and broad tail flattened laterally is clearly visible on the skeletons, the caudal vertebrae have long upper and short side branches. In some species the tail fin appears, which still increases the Stripping movement.
Sea turtles had to invent a completely different type of locomotion, because they can’t isviati the body of his shell. These animals developed planirovanie powerful forelimbs with which the turtles like flying in the water.
However, none of the above-described methods of navigation and types of skeleton is not similar to what is observed in sauropterygia, fossil reptiles, which first appeared in the Triassic. This group includes units Eosauropterygia and Plesiosauria, an extinct in the early Jurassic and late Cretaceous periods respectively. Like sea turtles, sauropterygia used strong planirovanie limbs. However, their tail remains well developed, though not too long. All plesiosaurs also had a terminal fin, it can be seen on a special area of the skeleton on their tail. The presence of such a fin, scientists have discovered more than a hundred years ago, but for some reason it is rarely portrayed in reconstructions and ignored in many studies. Was not clear the role of the tail in motion sauropterygia and what kind of plane it was moving.
Andrey Sennikov (Sennikov A. G.) from the Paleontological Institute of RAS Boriska investigated 14 samples (skeletons or prints) of marine reptiles, including representatives of sauropterygia, ichthyosaurs and crocodiles. The scientist drew attention to the fact that the caudal vertebrae of plesiosaurs spinous (vertical) shoots are very short, and the side extended. At the end of a special plot, which served as the basis of the horizontal fin is not bent down as in reptiles with a vertical tail. In addition, the body of plesiosaurs short, flattened in dorzoventral’no direction, making it impossible for him to bend. The sacrum of these reptiles is elongated and tightly connected with the pelvis, but the connection to the tail is more mobile. All these facts indicate that the locomotion of sauropterygia much more resembled modern whales and sirens and other water reptiles. The tail they had the flattened top and bottom, not sides, and moved in a vertical plane.