plesiosaura

Plesiosauria is an extinct order of marine reptiles that lived during the Mesozoic Era. These long-necked creatures are often depicted in popular culture as mythical sea monsters. They were characterized by their broad bodies, small heads, and four large flippers adapted for swimming. Plesiosaurs first appeared in the Late Triassic period and survived until the end of the Cretaceous period, disappearing with the non-avian dinosaurs.

There were two main types of plesiosaurs. Plesiosauromorphs, like Plesiosaurus, had generally long necks and shorter tails. Pliosauromorphs, such as Liopleurodon and Pliosaurus, were typically more robust, with shorter necks and longer tails, and were often apex predators. Their diet likely consisted of fish and squid, based on fossilized stomach contents and tooth morphology.

Fossils of plesiosaurs have been found worldwide, indicating a widespread distribution. Despite their aquatic lifestyle, they were reptiles and would have needed to breathe air. The exact method of reproduction is still debated, but evidence suggests they may have been viviparous, giving birth to live young. The demise of plesiosaurs, along with many other species, is linked to the Cretaceous-Paleogene extinction event.