Genus: Passumys CIFELLI, DAVIS & SAMES, 2014
Etymology: Latin, passus, "open"; in allusion to the broad central valley on the holotype.

Species: angelli CIFELLI, DAVIS & SAMES, 2014
Etymology: In honor of Jim Angella of Edgemont, South Dakota, in recongination of his scientific, longistic, and diverse other help to OMNH field parties through the years.

Holotype: OMNH 64191

Locality: OMNH V1243, near the mouth of Hell Canyon, Section 26, township 8S, Range 4E, N43°19', W103°37', about 17 ENE of Edgemont, Fall River County, South Dakota.

Horizon: Chilson Member, Lakota Formation.


Age: Berriasian-Valangian Stage, Lower Neocomian Subepoch, Lower Early Cretaceous Epoch, Early Cretaceous.

Material: Right m1.