Plesiosaur marine reptile hunting, illustration - stock illustration

Meyerasaurus sp. plesiosaur hunting a trilobite, illustration. The plesiosaurs were marine reptiles from the age of the dinosaurs, flourishing from the late Triassic period until the end of the Cretaceous period (200-66 million years ago).They existed in a variety of sizes; some with very long necks, and others with relatively short ones. The shortest plesiosaurids were around 1.5 m long, but their larger cousins grew to up to ten times that size.