A New Subspecies of Ground Squirrel (Spermophilus spilosoma) from Tamaulipas, Mexico

University of Kansas Publications Museum of Natural History
Volume 14, No. 8, pp. 121-124 March 7, 1962
University of Kansas Lawrence 1962
University of Kansas Publications, Museum of Natural History Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Theodore H. Eaton, Jr. Volume 14, No. 8, pp. 121-124 Published March 7, 1962 University of Kansas Lawrence, Kansas PRINTED BY JEAN M. NEIBARGER, STATE PRINTER TOPEKA, KANSAS 1962 29-1505

When A. H. Howell (N. Amer. Fauna, 56:1-256, 1938) revised the North American ground squirrels, he had no specimens of the spotted ground squirrel, Spermophilus spilosoma , from Tamaulipas. Thirteen years later, Hall (Univ. Kansas Publ., Mus. Nat. Hist., 5:38, 1951) listed the species for the first time from the state when he recorded as S. s. annectens 13 specimens from the barrier beach 88-89 miles south and 10 miles west of Matamoros.
In 1953, Mr. Gerd Heinrich collected 10 individuals of S. spilosoma from the coastal plain of eastern Tamaulipas that extend southward the known range of the species on the east coast of México, provide the first specimens from the mainland of Tamaulipas, and represent a new subspecies that is named and described below.
Spermophilus spilosoma oricolus new subspecies
Type. —Female, adult, skin and skull, No. 55497 Museum of Natural History, The University of Kansas; from one mile east of La Pesca, Tamaulipas, México; obtained on May 27, 1953, by Gerd Heinrich, original number 6933.
Diagnosis. —Size medium for species (see measurements); general color cinnamon buff, almost pure on dorsal surface of hind foot and dorsal and ventral midline of tail; spots well marked; postorbital constriction narrow; auditory bullae small; viewed from front, lower border of maxillary plate forming continuously concave line with jugal; zygomatic process of maxillary narrow, having anterior border concave.
Comparisons. —From Spermophilus spilosoma annectens (specimens from Padre and Mustang islands, Texas), S. s. oricolus differs as follows: larger in external dimensions but smaller in cranial dimensions; postorbital constriction narrower, 13.4 (13.2-13.8) instead of 14.0 (13.5-14.7); rostrum slightly broader; greatest distance between posterior border of maxillary plate and squamosal arm of zygoma longer, averaging 9.9 (9.7-10.2) instead of 9.6 (9.0-10.1); zygomatic process of maxillary, viewed dorsolaterally above lacrimal narrower, having anterior border concave instead of almost straight; when skull viewed from front, lower border of maxillary plate forming continuously concave line with jugal instead of almost a right angle where jugal and maxillary meet; ramus of lower jaw narrower; general color paler; upper surface of hind foot washed with cinnamon instead of yellowish; postauricular spot absent (usually present in annectens ).