Distribution.--Intermontane valleys and plains of southeastern Coahuila and probably adjacent parts of Zacatecas, San Luis Potosí and Nuevo León (see fig. 1).
Comparisons.--Cratogeomys castanops subnubilus needs close comparison only with Cratogeomys castanops planifrons, found to the east and from which subnubilus differs in: Body, hind foot and skull smaller; upper parts, in summer pelage, paler, more rufous-buff and less dark russet; underparts paler, more whitish and less blackish; hairs of hind foot reddish rather than blackish; zygomata more widely flaring; palate shorter, especially in females; rostrum broader, especially in females; nasals slightly smaller; squamosal breadth greater; incisors narrower, especially in males; maxillary teeth smaller. From Cratogeomys castanops rubellus Nelson and Goldman, found to the south in San Luis Potosí, subnubilus differs in: Body, hind foot and all parts of skull smaller; upper parts and underparts darker, more blackish and less rufous.
Remarks.--Cratogeomys castanops subnubilus is the smallest subspecies of C. castanops (see [tables 1 and 2]). This subspecies is dark and lives at high elevations (5500 ft. to 6800 ft.) in deep valley soils in relatively isolated intermontane valleys and elevated plains. It is differentiated to a much higher degree from adjacent subspecies of C. castanops than is usual in this species, and no intergrades between subnubilus and other subspecies have been taken. In the Sierra Guadalupe, subnubilus was trapped at 6700 feet within two miles of a place where subsimus was taken at 6500 feet.
Specimens examined.--Total, 31, from: 1 mi. N Agua Nueva, 5500 ft., 1; Domingo Cañon, Sierra Guadalupe, 6700 ft., 11 mi. S and 4 mi. W General Cepeda, 1; Carneros, 6800 ft., 6 (BSC); 1 mi. S Carneros, 6000 ft., 4; 2 mi. W San Miguel, 5500 ft., 3; 8 mi. N La Ventura, 6000 ft., 10; La Ventura, 5600 ft, 6 (BSC).
Cratogeomys castanops planifrons Nelson and Goldman
| 1934. | Cratogeomys castanops planifrons Nelson and Goldman, Proc. Biol. Soc. Washington, 47:146, June 13, type from Miquihuana, 5000 ft., Tamaulipas (listed, by mistake, as southern Nuevo León). |
Distribution.--Elevated montane valleys of Sierra Madre Oriental of extreme southeastern Coahuila, south and east into southwestern Nuevo León and Western Tamaulipas (see [fig. 1]).
Remarks.--Specimens from Coahuila assigned to planifrons compare favorably with topotypes of this subspecies although they are slightly larger in cranial dimensions (see [tables 1 and 2]). This small subspecies is darker and slightly larger than subnubilus but in other ways is most closely related to subnubilus. Cratogeomys c. planifrons shows little relation to other adjacent subspecies, including tamaulipensis, subsimus and rubellus, all of which are considerably larger and paler.
Cratogeomys castanops planifrons is found in both deep and shallow soils of the high, open valleys of the Sierra Madre Oriental; in Coahuila it was taken at elevations as low as 7200 feet and as high as 8700 feet.