Phillip M. Youngman

“ Specimens from Lake La Jara, New Mexico, and nearby localities in Colorado may be separated from topotypes of T. b. aureus on the basis of color only. The topotypes of T. b. aureus are mostly pale; some, however, are dark. The number of pale specimens in any given series decreases gradually in a clinal pattern from west to east. ”

“ The characters originally used to describe T. b. optabilis are of the type that vary between populations only a few miles apart, or often vary within a population. The skulls of specimens from Coventry are not lighter in structure than those of T. b. aureus. The premaxillae are not narrower, nor is the frontal region narrower or more constricted than in T. b. aureus.
The name Thomomys bottae apache, given to specimens from Lake La Jara, New Mexico, by Bailey (1910:79) , and later applied to specimens from Colorado by Bailey (1915:75) , is here also placed in synonymy under T. b. aureus. ”

“ Topotypes of T. b. cultellus most closely resemble those of T. b. internatus but differ as follows: darker; zygomatic arches more widely spreading, not so nearly parallel; nasals not so wide; bullae slightly more inflated.
For a comparison with T. b. rubidus see the account of that subspecies.
Remarks.—Kelson (1951:64) named T. b. cultellus on the basis of six dark specimens (Dark Reddish Brown 5YR 3/4 and 2/2) . Nowhere else within the range of this subspecies, as defined by Kelson, do any specimens resemble the topotypes in color. ”

“ Geographic distribution of Thomomys bottae in southwestern Colorado.
1. T. b. howelli 2. T. b. aureus 3. T. b. pervagus 4. T. b. cultellus 5. T. b. internatus 6. T. b. rubidus
In studying geographic variation, greater emphasis was placed on females than on males. As noted by Grinnell (1931:4) , males vary more than females, especially in length of rostrum and associated nasal measurements. ”

“ Three criteria of adulthood are: (a) suture obliterated between supraoccipital and exoccipital, (b) suture at least partly obliterated between basisphenoid and basioccipital, (c) supraorbital crests not widely separated and almost parallel. In males the crests encroach on the lateral borders of the interparietal; in females the crests approach the lateral borders of the interparietal but are more widely separated than in males. ”

“ Holotype.—Adult male, skin and skull, number 70919, United States National Museum, Halls Peak, Mora County, New Mexico; January 13, 1895, obtained by C. Barber.
Distribution.—Raton Section of the Great Plains in northern New Mexico and extreme southern Colorado (see fig. 1) .
Distinctive characters.—Dark (topotypes) ; size medium (see measurements) ; posterior tongues of premaxillae short; posterior margins of nasals forming a V (see fig. 5) .
Comparisons.—From T. b. pervagus, topotypes of T. b. cultellus differ as follows: darker, not so reddish; smaller; skull smaller ”

“ My findings indicate that T. b. cultellus is not smaller, that its skull is not smaller and not less angular, and that the tympanic bullae are not less pointed ventrally. Further collecting is needed better to limit and diagnose this subspecies.
Specimens examined.—Total 13. Colorado: Las Animas Co.: Fishers Peak, about 8000 ft., 1 (USNM) . New Mexico: Union Co.: Near Folsom, 4 [pg 376] (CMNH) ; Colfax Co.: Philmont Ranch, Cimarroncito, 8100 ft., 2. Mora Co.: Halls Peak, 6 (USNM) .
Figs. 2-7. Dorsal views of skulls of Thomomys bottae. × 1.
Fig. 2. Thomomys b. aureus, 3 mi. ”

“ Cotopaxi, 1 (CSU) ; 5 mi. S Cotopaxi, 12. El Paso Co.: 1-1/4 mi. S Colorado Springs, 2; 9 mi. SSW Colorado Springs, 2; 17 mi. S Colorado Springs, 1. Custer Co.: 2-1/2 mi. S Wetmore, 3; Santa Fe Drive and 20th Lane, Blende, 1; St. Charles Mesa, 5600 ft., 2 (CSU) ; Fork of Huerfano and Cucharas rivers, 2 (CMNH) . Huerfano Co.: 11 mi. WNW Gardner, 7000 ft., 3; Gardner, 7000 ft., 2 (USNM) ; 1-1/2 mi. S Redwing, 3; Bear Creek, near Walsenburg, 2 (CSU) ; 1 mi. E La Veta, 8; 5 mi. SE La Veta, 2.
Thomomys bottae cultellus Kelson
Thomomys bottae cultellus Kelson, Univ. ”