Choristodera

The Choristodera are one of those highly specialised Mesozoic groups that don't seem to be easily placed on the diapsid family tree. Although generally considered a minor group, they include a diverse range of morphotypes, including lizard, crocodilian, and even sauroptyerygian mimics. They were unaffected by the end Cretaceous extinction, and survived well into the Cenozoic. Had they continued only another twenty million years or so, we would have had five rather than four extant orders of reptiles. MAK120708

Image: Champsosaurus, from The Simon and Schuster Encyclopedia of Dinosaurs and Prehistoric Creatures