Species: antirrhopus OSTROM, 1969
Etymology:

Holotype: YPM 5205

Locality: YPM 64-75, NE 1./4, Sec. 17, T7S, R24E, Carbon County, Montana.

Horizon: Cloverly Formation.

Biostratigraphy:

Age: Cashenranchian, Aptian-Albian Stage, middle Gallic subepoch, lower Cretaceous Epoch, Early Cretaceous.

Material: A complete left pes and an incomplete right pes.

Note: MARSALL, BRINKMAN, LAU & BOWMAN, 1998 show that the second pedal digit PII had osteomyelithis.