During the Mesozoic era, many groups of reptiles became adapted to life in the seas, including such familiar clades as the ichthyosaurs, plesiosaurs, placodonts, and mosasaurs.

The marine reptiles depicted here are in three groups: The Sauropterygians (plesiosaurs and nothosaurs), the dolphin-like Ichthyopterygians and the fearsome mosasaurs.

The pictures of marine reptiles are organised by group (Sauropterygia, Ichthyopterygia and mosasaurs) on these tabbed pages.

The Sauropterygia ("lizard flippers") is a group of very successful extinct aquatic reptiles that flourished during the Mesozoic. It comprises the plesiosaurs and "nothosaurs". They are united by a radical adaptation of their shoulder, designed to support powerful flipper strokes.

Elasmosaurus

The Ichthyopterygia is group of marine reptiles that lived from the Early Triassic to Late Cretaceous though their heyday was during the Jurassic. They were fishlike with a spindle-shaped body, high tail fin, triangular dorsal fin and paddlelike legs. They gave birth to live young.

Shonisaurus

Mosasaurs were serpentine marine reptiles. During the last 20 million years of the Cretaceous Period, with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators. Mosasaurs breathed air and were powerful swimmers that were well-adapted to living in the warm, shallow epicontinental seas prevalent during the Late Cretaceous Period. Mosasaurs were so well adapted to this environment that they gave birth to live young, rather than return to the shore to lay eggs, as sea turtles do.

Trinacromerum