Range.—Southeastern Wyoming, northeastern Colorado, northwestern half of Nebraska and southwestern South Dakota; marginal occurrences are: in Wyoming, Casper, Sun and Ft. Steele; in Colorado, Loveland, Hugo and Akron; in Nebraska, Birdwood Creek, Neligh and Valentine; in South Dakota, Batesland and Buffalo Gap.
Diagnosis.—Size medium (see measurements). Color light, entire dorsal surface between Light Ochraceous-Buff and Ochraceous-Buff, purest on sides and flanks; upper parts but lightly washed with black; arietiform markings, plantar surfaces of hind feet, pinnae of ears and dorsal and ventral stripes of tail, blackish. Skull medium in size; jugal weak; braincase slightly inflated; nasals slightly flared distally.
Comparisons.—From Dipodomys ordii terrosus, D. o. luteolus differs as follows: Size smaller, except that tail and ear are longer; color lighter in all pigmented areas; skull smaller in every measurement taken; auditory bullae less inflated; zygomatic processes of maxillae smaller; cutting edge of upper incisors narrower; zygomatic arch weaker.
From Dipodomys ordii priscus, D. o. luteolus differs in: Size larger except hind foot which is shorter; dorsal and ventral stripes of tail, plantar surfaces of hind feet, arietiform markings and pinnae of ears, in most specimens, darker; auditory bullae less inflated; nasals shorter; rostrum wider; total length of skull shorter; zygomatic arch weaker; foramen magnum more ovate.
From Dipodomys ordii evexus, D. o. luteolus differs as follows: Hind foot longer; color lighter in all pigmented areas; auditory bullae more inflated; pterygoid fossae more expanded laterally; width across maxillary arches less; interorbital region narrower; zygomatic arch weaker; external auditory meatus almost round as opposed to ovoid.
Comparison with Dipodomys ordii richardsoni is made in account of that subspecies.
Remarks.—Dipodomys ordii luteolus resembles D. o. priscus in size and color but can readily be told from it and D. o. richardsoni when specimens from the central portions of the ranges of the subspecies are compared. At and near the periphery of the range, especially in that part which adjoins the range of D. o. richardsoni, intergradation occurs. Specimens from Kennedy, Perch and Neligh, Nebraska, approach D. o. richardsoni in the shape of the pterygoid fossae and nasal bones, but in all other characters they resemble D. o. luteolus to which subspecies they are here referred. Specimens from Loveland and 20 miles east of Avalo, Colorado, show intergradation with D. o. richardsoni in the width of the rostrum and size of the zygomatic arch but are referable to D. o. luteolus.
No specimens here referred to D. o. luteolus were found to intergrade with D. o. priscus.
Specimens examined.—Total, 250, distributed as follows:
South Dakota: Perkins County: 9 mi. N Bison, 8 (MVZ). Meade County: Smithsville, 2 (USBS). Jackson County: 20 mi. SSE Phillip, in Haakon County, 1 (MVZ). Custer County: Elk Mountain, 1 (MHS); Buffalo Gap, 2 (USNM). Bennett County: Big Spring Canyon, Batesland, 7 (CNHM); Rosebud Indian Agency, 1 (USBS).