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Class Mammalia
Order Rodentia
Family Sciuridae

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Spermophile Ground Squirrels—Spermophile Ground Squirrels // Callospermophilus lateralis—Golden-mantled Ground Squirrel // Ictidomys/Xerospermophilus)—Ictidomys or Xerospermophilus Ground Squirrel // Ictidomys tridecemlineatus—Thirteen-lined Ground Squirrel // Otospermophilus beecheyi—California Rock Squirrel // Otospermophilus bensoni—Benson Rock Squirrel // Otospermophilus variegatus—Rock Squirrel // "Spermophilus" cochisei—Cochise Ground Squirrel // Urocitellus elegans—Wyoming Ground Squirrel // Xerospermophilus spilosoma—Spotted Ground Squirrel

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Otospermophilus beecheyi (Richardson 1829)—California Ground SquirrelRegional Pleistocene distribution of Otospermophilus beecheyi

Synonyms. Spermophilus beecheyi

Sites.

Late Blancan/Early Irvingtonian: Elsinore: Mimomys (Pajak et al. 1996: aff.).

?Irvingtonian/Rancholabrean: Emery Borrow Pit (Jefferson 1991b).

Rancholabrean: Harbor Freeway, Athens (Jefferson 1991b).

Sangamon: Newport Bay Mesa (Jefferson 1991b: cf.); San Pedro Lumber Co. (Jefferson 1991b).

Wisconsin: Costeau Pit (Jefferson 1991b).

Mid Wisconsin: McKittrick (Schultz 1937: cf.).

Mid/Late Wisconsin: Diamond Valley (Springer et al. 2009); Rancho La Brea (Stock and Harris).

Literature. Jefferson 1991a; Pajak et al. 1996; Schultz 1937; Springer et al. 2009; Stock and Harris 1992.

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Otospermophilus bensoni (Gidley 1922)—Benson Ground SquirrelRegional Pleistocene distribution of Otospermophilus bensoni

Synonyms. Citellus bensoni, Spermophilus bensoni

Fig. 1. Otospermophilus bensoni Holotype. Last left upper molar, crown view (3); right upper molar (3a, 3b) probably of same individual; lower cheek teeth in fragment of jaw of left side, crown view. After Gidley 1922.

Teeth of Otospermophilus bensoni

Gidley (1922) described O. bensoni as follows:

   Type.—A first or second upper molar of the right side and a last upper molar of the left side (catalog No. 10531, U.S. Nat. Mus.).
   Paratype.—The cheek-tooth series of a left lower jaw (catalog No. 10532, U.S. Nat. Mus.).
   Locality.—Both from the Benson locality.
   Description.—Length of cheek-tooth series (estimated from measurements of the paratype), 10.3 millimeters; upper molar of about the same proportion as the corresponding one of C. cochisei at the base but much narrower at the summit, owing to the greater slope of the inner wall of the protocone; the three transverse lophs about equal in length, the posterior one being broken up into two distinct but slightly joined cuspules, the inner one of which is a rounded cone entirely disconnected from the protocone.
   An upper m3 which I associate with the type specimen, like that of C. beecheyi, has a relatively small heel portion as compared with living species, and in addition there is a well defined isolated cone-shaped cuspule near the center of the posterior basin.
   This species seems to approach C. beecheyi much more closely than any other living species but differs from it in a few apparently important particulars. In C. beecheyi the crowns of the upper molars are relatively narrower than in the fossil species, being nearly as long as wide; the lingual wall of the protocone is less sloping, and the exterior or buccal face of this cusp is much more sloping. Other differences noted in the living species are the generally less broken up condition of the posterior transverse lophs; the somewhat shallower transverse valleys, the posterior one of which usually has a small cuspule at its external entrance; and the relatively broader and less completely inclosed posterior valley of the last upper molar. Beyond the fact that the last lower molar, like the upper, is relatively smaller, and the valleys and cusps are somewhat more sharply defined than in C. beecheyi, there is little to distinguish between the lower cheek teeth of that species and C. beecheyi.

Sites.

Late Blancan: 111 Ranch (Morgan and White 2005: ?); California Wash (Morgan and White 2005); San Simon Fauna (Morgan and White 2005: ?); Tecopa Lake Beds (Woodburne and Whistler 1991: cf.).

Literature. Morgan and White 2005; Woodburne and Whistler 1991.

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Otospermophilus variegatus (Erxleben 1777)—Rock SquirrelRegional Pleistocene distribution of Otospermophilus variegatus

Synonyms. Citellus grammarus, Spermophilus grammarus, Spermophilus variegatus.

Dentaries of Sciurus aberti and Otospermophilus variegatusRock Squirrels look more like they should be tree squirrels than ground squirrels, and indeed it is not rare to see them climbing. They are about the size of our Southwestern species of Sciurus, and size alone will separate them from other regional ground squirrels .

The Rock Squirrel currently is distributed throughout the region, lowlands to high mountains, where rocky terrain or steep-banked arroyos occur, but are otherwise absent from desert and grassland (Findley et al. 1975).

Fig. 1. As seen here, Sciurus aberti (top) and Otospermophilus variegatus are very close in size. Dental characteristics and configuration of the dentary (especially the length and depth of the diastema) will separate the two. Characters of the posterior dentary also are quite different, but often missing in fossil material.

NPS photograph of Otospermophilus variegatusFig. 2. Rock Squirrel. National Park Service photograph by Sally King.

Sites.

Medial Irvingtonian: SAM Cave (Rogers et al. 2000).

Rancholabrean: Papago Springs Cave (Czaplewski and Mead et al. 1999; Skinner 1942)

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

Mid Wisconsin: Screaming Neotoma Cave (Glennon 1994); U-Bar Cave (Harris 1987).

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

Mid/Late Wisconsin/Holocene: Jimenez Cave (Messing 1986); Sierra Diablo Cave (UTEP).

Late Wisconsin: Antelope Cave (Reynolds, Reynolds, Bell, and Pitzer 1991); Dust Cave (Harris and Hearst 2012); Murray Springs (Mead et al. 2005); Muskox Cave (Logan 1981); U-Bar Cave 14-15 ka (Harris 1989); U-Bar Cave 15-18 ka (Harris 1989); U-Bar Cave 18-20 ka (Harris 1989); Upper Sloth Cave (Logan and Black 1979); Vulture Cave (Mead and Phillips 1981).

Late Wisconsin/Holocene: Burnet Cave (Schultz and Howard 1935); Conkling Cavern (UTEP); Deadman Cave (Mead et al. 1984); Fowlkes Cave (Dalquest and Stangl 1984b); Kokoweef Cave (Reynolds, Reynolds, et al. 1991: cf.); Pendejo Cave (UTEP); Stanton's Cave (Olsen and Olsen 1984); Williams Cave (Ayer 1936)

Literature. Ayer 1936; Czaplewski and Mead et al. 1999; Dalquest and Stangl 1984b; Findley et al. 1975; Glennon 1994; Harris 1987, 1989, 1993c; Harris and Hearst 2012; 1991b; Logan 1981; Logan and Black 1979; Mead and Phillips 1981; Mead et al. 1984, 2005; Messing 1986; Olsen and Olsen 1984; Reynolds, Reynolds, et al. 1991; Reynolds, Reynolds, Bell, and Pitzer 1991; Rogers et al. 2000; Schultz and Howard 1935; Skinner 1942; Tebedge 1988.

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Last Update: 1 Jul 2014