CLIDASTES

genus of extinct, ancient marine reptiles, the mosasaurs, related to modern lizards. Clidastes is found as a fossil in Late Cretaceous marine rocks in North America (the Cretaceous Period ended 66.4 million years ago). Excellent fossil remains have been found in the chalk deposits of Kansas. Clidastes grew to large size; the head alone was about 60 centimetres (24 inches) long and was equipped with many sharply pointed, curved teeth. The neck was short, but the body and tail were long and relatively slim. The tail was probably the main means of propulsion, with the poorly developed limbs, which terminated in broad appendages, providing directional control. Clidastes was clearly an efficient swimming predator and probably fed largely on fish, as well as on ammonite cephalopods, mollusks related to the squids and pearly nautilus of today. It is uncertain whether Clidastes emerged on land to reproduce.