Cernictis hesperus was described as an unusual mustelid carnivore from the Pinole Tuff Local Fauna of California (Hall 1935). The Pinole Tuff has been dated radiometrically at 5.3-5.5 Ma (Tedford et al. 2004), making the fauna latest Hemphillian (Hh4, latest Miocene) in age. Hall's new genus and species was based on a mandibular fragment with p4-m1. The new species of Cernictis described here is named from a mandible with p2-m1 from the Bidahochi Formation at White Cone Peak in northeastern Arizona. White Cone Peak, a prominent topographic feature on the Hopi Indian Reservation (formerly Hopi-Navajo joint-use land) in Navajo County, Arizona, approximately 70 km north of Holbrook, has produced a diverse fossil assemblage (Stirton 1936;
Uyeno and Miller 1965;
Parmley and Peck 2002;
Hodnett 2010). The White Cone Local Fauna was collected from the upper member of the Bidahochi Formation (Repenning and Irwin 1954), approximately 20 m above the base of the volcanic middle member. A basalt flow, which can be traced into the middle member of the Bidahochi Formation at Roberts Mesa, approximately 10 km northwest of White Cone peak, was dated at 6.85 ± 0.16 Ma (Damon and Spencer 2001), which places the White Cone fauna in the late Hemphillian (Hh3).
The holotype of Cernictis repenningi n. sp. was collected by C. Repenning during a geologic investigation of the Bidahochi Formation by the USGS (Repenning and Irwin 1954). He (Repenning et al. 1958, p.129) described the specimen as belonging to a "marten-like animal." It is in the collections of the University of Arizona Laboratory of Paleontology (UALP). Two additional specimens collected from White Cone Peak in 1974 are referred to C. repenningi because they are of the appropriate size. They are designated by the prefix UALP wc.