Late Cretaceous

Hell Creek Formation

Wibaux County, Montana, USA

Excellent 0.7 inch vertebra.

Reptile, Champsosaur.  Family Champsosauridae.

Champsosaurus is a genus that belongs to a lesser-known order of reptiles (Choristodera) that appeared during the Jurassic and lived across the Cretaceous.  They even survived the K/T extinction but became rare by the Eocene, dying out around the end of the epoch.  It is known from the Late Cretaceous to Paleocene of Wyoming, Montana, the Dakotas, and Canada.  Other champsosaurs and choristoderes are also known from Europe and Asia.

Champsosaurs were crocodile-like in form and probably in their lifestyle as well though they appear to be more closely-related to lizards.  Their thin, needle-like teeth are hard to find.  The distinctive vertebrae are their most commonly found remains.