Plesiosaurus

Name meaning:

Close to a lizard

Period of life:

199–193 million years ago

Period:

Jurassic period

Habitat:

Marine environment

Taxonomy:

Sauropodomorphs

Countries:

Jurassic period Plesiosaurus | 3D Dinopedia

Juramaia

Iguanodon

Plesiosaurus (199–193 million years ago)

What the name means: “Close to a lizard” (from the Greek words plesios, meaning close, and sauros, meaning lizard). It was named this because its anatomy seemed to 19th-century scientists closer to that of modern reptiles than to ichthyosaurs.

Plesiosaurus was an extinct predatory marine reptile, the type representative of the order Plesiosauria within the superorder Sauropterygia. Contrary to a common belief, plesiosaurs were not marine dinosaurs. They were a separate evolutionary branch of reptiles — sauropterygians — that adapted to life in the water. This long-necked reptile was the first of its kind to be studied by scientists, which is why the entire order of marine reptiles received the name “plesiosaurs.”

The true Plesiosaurus was by no means a giant, unlike many of its long-necked relatives. It reached 3–3.5 meters in length. Its body looked as though nature had assembled the animal from several different parts. It almost seems as if a sea snake had put on the body of a turtle.

Plesiosaurus was a predator, but not a monster that tore prey to pieces. Its small head did not allow it to seize large victims. Its jaws were armed with thin, sharp teeth that curved slightly backward. This kind of mouth worked like a trap: grab a slippery fish or belemnite, hold on to it, and keep it from escaping. These teeth were poorly suited for slicing flesh, but they were almost ideal for catching fast, slippery prey.

Plesiosaurus swam with the help of four powerful flippers. It was true underwater flight: the flippers moved up and down, creating lift and thrust.

Modern studies show that many plesiosaurs probably had a high metabolic rate and could maintain a body temperature above that of the surrounding water. This does not make them “mammals in scales,” but it tells us something important: this was not a sluggish, cold lizard, but an active marine predator, well adapted to life in the vast Jurassic world.

Plesiosaurus lived in the Early Jurassic, about 199–193 million years ago, in warm shallow seas that covered part of what is now Europe. These were not bottomless ocean deserts, but rich marine environments full of life: fish, ammonites, belemnites, other marine reptiles — a true Mesozoic underwater world.

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