Late Cretaceous

Hell Creek Formation

Carter County, MT, USA

Two 4mm teeth of a rare hybodont shark

Shark.

Hybodont sharks appeared during the Devonian Period and survived the end-Permian mass extinction becoming the dominant shark group of the Triassic and Jurassic.  The group went into decline across the Cretaceous and disappeared during the K/T extinction.  Lissodus selachos was one of the last species and one of the few selachians found in the Hell Creek Formation.