elasmosaurid

Elasmosauridae is a family of extinct marine reptiles within the order Plesiosauria. Members are among the best known long-necked plesiosaurs and include genera such as Elasmosaurus, Albertonectes, and Thalassomedon. They are distinguished by very long necks relative to their bodies, a small skull, and limbs modified into broad flippers for swimming.

Physical characteristics include elongated cervical vertebrae that give the neck a distinctive, extended profile. The skull tends to be relatively small, and the teeth are typically sharp and conical, suited to grasping slippery prey such as fish and cephalopods. The body is compact with a broad torso and four paddle-like limbs that provided propulsion in the aquatic environment.

Fossils attributed to elasmosaurids have been found on multiple continents, with notable discoveries in North America and Europe. They lived from the Early to Late Cretaceous period, roughly 130 to 66 million years ago, and they disappeared at the end of the Cretaceous with the mass extinction event.

Ecology and behavior are inferred from skeletal anatomy and wear patterns on teeth. Elasmosaurids were marine carnivores that occupied various niches in coastal to open-ocean ecosystems. Their long necks may have allowed them to approach prey with the body relatively stationary, aiding stealth, though precise feeding strategies likely varied among species and environments.

Taxonomically, elasmosaurids form one of the major lineages within plesiosaurs and are often contrasted with shorter-necked relatives. Their distinctive morphology makes them a recognizable component of Mesozoic marine faunas.