Heliscomyidae
Heliscomyidae is a family of extinct rodents from the mid-Tertiary of North America related to pocket gophers and kangaroo rats and their relatives. The family contains four genera, Apletotomeus, Heliscomys, Passaliscomys, and Tylionomys. McKenna and Bell placed the first two genera in synonymy, with Heliscomys as the senior synonym.
Characteristics
Heliscomyids are distinguished from other geomyoid rodents by several characteristics of the skull including the fusion of three cranial foramina, elongation of the incisive foramina, and an unusual position of the mental foramen.
Taxonomy
Heliscomyidae is a member of the clade Geomyoidea, a group of rodents that also includes the families †Eomyidae, †Florentiamyidae, Heteromyidae, and Geomyidae. The following cladogram showing interrelationships among geomyoid families follows Korth et al. :