Mammalia - Allotheria - Eucosmodontidae

Synonym: Stygimys cupressus Fox 1989

Full reference: R. E. Sloan and L. Van Valen. 1965. Cretaceous mammals from Montana. Science 148(3667):220-227

Belongs to Stygimys according to D. L. Lofgren et al. 2005

Sister taxa: Stygimys camptorhiza, Stygimys gratus, Stygimys jepseni, Stygimys teilhardi, Stygimys vastus

Type specimens:

• Stygimys kuszmauli: U.M.V.P. 1478, a mandible (left lower jaw fragment with I and alveoli for P4 and M1). Its type locality is Bug Creek Anthills, which is in a Puercan terrestrial horizon in the Hell Creek Formation of Montana.
• Stygimys cupressus: Its type locality is Long Fall Horizon, Rav W-1, which is in a Puercan fine channel fill siliciclastic in the Ravenscrag Formation of Canada.

Ecology: scansorial omnivore

Average measurements (in mm): M1 5.32 x 2.44, m1 4.44 x 1.87