Polycotylids

Polycotylids are a group of extinct marine reptiles that lived during the Late Triassic and Early Jurassic periods, approximately 230 to 180 million years ago. They are characterized by their unique body structure, which includes a long, slender neck and a large, flat head with a beak-like mouth filled with sharp teeth. The most well-known polycotylid is the ichthyosaur, which is often referred to as a "fish lizard" due to its aquatic lifestyle and reptilian ancestry.

Polycotylids are believed to have been semi-aquatic creatures, spending most of their time in the water but occasionally coming onto land. They were active predators, feeding on a variety of marine organisms such as fish, squid, and other reptiles. Their long necks and powerful jaws allowed them to capture prey with precision, while their streamlined bodies helped them swim efficiently.

The fossil record of polycotylids is extensive, with numerous species discovered around the world. They are known from both complete and partial skeletons, as well as isolated teeth and bones. The most famous polycotylid fossils come from the marine deposits of the United Kingdom, particularly from the Jurassic Coast in Dorset.

Despite their unique appearance and adaptations, polycotylids are not closely related to modern reptiles. Instead, they are part of a larger group called diapsids, which also includes crocodilians, birds, and dinosaurs. The study of polycotylids provides valuable insights into the evolution of marine reptiles and their role in the Triassic and Jurassic ecosystems.