Main Menu

Class Mammalia
Order Rodentia
Family Cricetidae
Subfamily Neotominae
Genus Peromyscus


Peromyscus nasutus (J. A. Allen 1891)—Northern Rock MouseRegional Pleistocene distribution of Peromyscus nasutus.

Synonyms. Peromyscus difficilis.

At various times, there have been questions as to the specific status of northern populations of P. difficilis-like mice, and these populations have been known as P. difficilis during part of the 20th century and as P. nasutus both earlier and later in the century.

Modern samples of Peromyscus around Dry and U-Bar caves produced none of this species. Cornely et al. (1981) found them relatively common above 1900 m in Guadalupe Mountains National Park, but their lowest-elevation specimen was from 1585 m. The modern general distribution is in rocky areas from north-central Colorado south well into Mexico, including most of New Mexico and Trans-Pecos Texas and eastern Arizona.

Lundelius (1979) referred large mandibles (length of m1-2 >3.26 mm) with stylids and lophids on m1 and m2 to P. difficilis. Since then, Dalquest and Stangl (1983) undertook a study of Trans-Pecos Peromyscus, including this species. They found that a combination of alveolar length of the lower toothrow >4.1 mm, absence of a well developed incisor-base capsule, a deeply divided anteroconid, and presence of stylids and lophids on m1 indicate P. nasutus, though speculating that large P. truei and small P. nasutus might be difficult to discriminate.

As noted by Dalquest and Stangl (1983), the major danger in identification is confusing P. nasutus with P. truei, and discriminant scores do overlap to a degree. Nevertheless, most UTEP identifications not otherwise qualified seem firm.

The Northern Rock Mouse is the most common identified species from U-Bar Cave and occurred in both mid Wisconsin and late Wisconsin deposits.


Rancholabrean: Anthony Gap Cave (UTEP: cf.)

Mid Wisconsin: Pendejo Cave (UTEP); U-Bar Cave (Harris 1987; UTEP).

Mid/Late Wisconsin: Dark Canyon Cave (Tebedge 1988).

Mid/Late Wisconsin/Holocene: Sierra Diablo Cave (UTEP).

Late Wisconsin: Algerita Blossom Cave (UTEP: cf.); Harris' Pocket (UTEP); U-Bar Cave (UTEP).

Late Wisconsin/Holocene: Fowlkes Cave (Dalquest and Stangl 1984b).


Early/Early-Mid Wisconsin: Rm Vanishing Floor (Harris 1993c: ?).

Literature. Cornely et al. 1981; Dalquest and Stangl 1983, 1984b; Harris 1987, 1993c; Lundelius 1979; Tebedge 1988.


Last Update: 9 Mar 2013