Species: atrox BAKKER & CARPENTER, 1990
Etymology: Latin, atrox, "ferocious, cruel."
Holotype: UCM 59089 (incorrectly given as UCM 47257 in BAKKER and CARPENTER, 1990)
Locality: Main Breakfast Bench Quarry, UCM Loc. 80001, pine Tree Ridge, Sec. 13, Township 22, Range 76 West, Albany County, Wyoming.
Horizon: Member? Morrison Formation.
Biostratigraphy: Zone?
Age: Age?, Stage?, Malm Epoch, Late Jurassic or Early Cretaceous.
Material: Fragmentary dentary with LI3-4, LC1, LP2, 3, 4 and alveoli for LI1-2
and LM5.