Oryctodromeus

Oryctodromeus (from Ancient Greek ὀρυκτήρ (oruktḗs), meaning "digger", and δρομαῖος (dromaîos), meaning "runner") is an extinct genus of small orodromine thescelosaurid dinosaur. Fossils are known from the Late Cretaceous Blackleaf Formation of southwestern Montana and the Wayan Formation of southeastern Idaho, USA, both of the Cenomanian stage, roughly 105-96 million years ago. A member of the small, presumably fast-running herbivorous family Thescelosauridae, Oryctodromeus is the first non-avian dinosaur published that shows evidence of burrowing behavior.

==Description== thumb|left|Restoration of an individual in its burrow Oryctodromeus was originally described as lacking ossified tendons in the tail. However, specimens from the Wayan Formation demonstrate the presence of a thick tendon lattice in the dorsal, sacral, and caudal columns of some specimens; perhaps indicating more flexibility in ossified tendons than has previously been supposed. Adaptations in the jaws, forelimbs, and pelvis were described in the Blackleaf specimens that could have helped move and manipulate soil. Additional material from the Wayan Formation demonstrates further adaptations for digging in the femur.