Genus: Stygivenator OLSHEVSKY, FORD & YAMAMOTO, 1995
Etymology: Stygi-, Latinized combining form of Styx, one of the three rivers of Hades, the underworld of Greek mythology, refereeing to the Hell Creek Formation, in which the type specimen was discovered; and Latin, -venator, "hunter”; thus, “Hell Creek hunter”.

Species: molnari (PAUL, 1988) OLSHEVSKY, FORD & YAMAMOTO, 1995
= Aublysodon molnari PAUL, 1988
Etymology: In honor of Ralph Molnar.
= "JORDAN THEROPOD" MOLNAR, 1978

Holotype: LACM 28471

Locality: On the Lester D. Engdahl Ranch (not, as originally noted, the F. S. McKeever Ranch), S34, T21N, R37E, near Jordan, Garfield County, Montana.

Horizon: Hell Creek Formation.

Biostratigraphy:

Age: Lancian age, upper Maastrichtian Stage, uppermost Senonian subepoch, Upper Gulf Epoch, Late Cretaceous.

Material: Partial skull, including a premaxillary tooth, most of both maxillae, nasals, and frontals, the parietal and portions of the surangular and dentaries.

Last premaxillary tooth, not the first maxillary.