1.37" (3.5 cm) Postouchus (Rauisuchid) tooth. From the Chinle Formation found in Navajo County Arizona. From the Late Triassic about 205-215 million years old.  

Postosuchus is a Rauisuchid archosaur. Rauisuchids are a relative of crocodiles but were like land dwelling, apex predators during the Late Traissic. Their legs were directly underneath their body to allow for running on land to hunt their prey.