Analysis of the Crotaphytus collaris complex reveals at least eight subspecies in two distinct groupings. The collaris-complex containing C. c. auriceps, C. c. baileyi, C. c. fuscus, and C. c. collaris lies essentially to the east of the Colorado River. The greatest portion of the western-complex containing C. c. bicinctores, C. i. vestigium, C. c. dickersonae and C. i. insularis lies to the west of the Colorado River except through western Arizona and northern Mexico. Two previously undescribed subspecies, C. c. bicinctores and C. i. vestigium, are described and named.
Smith, Nathan M. and Tanner, Wilmer W.
"Two new subspecies of Crotaphytus (Sauria: Iguanidae),"
Great Basin Naturalist: Vol. 32
, Article 3.
Available at: http://scholarsarchive.byu.edu/gbn/vol32/iss1/3