Phytosaur
Late Triassic (Norian)
Upper Redonda Formation, Chinle Group
Quay County, New Mexico, USA

15mm tooth on 48mm matrix.

Phytosaurs were an extinct group of archosaurs that looked like crocodiles  The fast way to tell their skulls apart is that crocodilians have their nasal opening at the end of their snouts while phytosaurs have theirs just in front of their eyes.  Some species of which were larger than any crocodile living today, exceeding 25 feet in length.  The group disappeared during the end-Triassic mass extinction.