Taxonomy and Distribution
| ||Ridgenose Rattlesnake Crotalus willardi (61615)|
| ||The species' range extends from southeastern Arizona and extreme southwestern New Mexico south in the Sierra Madre Occidental through north-central and northeastern Sonora to western Chihuahua and (possibly disjunctly) to southern Durango and western Zacatecas, Mexico, at elevations of about 1,460 to 2,750 m (4,790 to 9,020 feet) (Campbell and Lamar 2004).
Subspecies obscurus occurs locally in the Animas Mountains (New Mexico), Peloncillo Mountains (Arizona and New Mexico), and Sierra de San Luis (Sonora and Chihuahua, Mexico) (Campbell et al. 1989, Holycross and Smith 1997, Campbell and Lamar 2004).
Subspecies willardi occurs in the Huachuca, Patagonia, Santa Rita, and Whetstone mountains of Arizona and southward into the Sierra de los Ojos, Sierra de Cananea, and Sierra Azul in north-central Sonora (Thirkhill and Starrett, 1992, Campbell and Lamar 2004).|
| ||amabilis||Sierra del Nido|
| ||meridionalis||Southern Durango, North Western Zacatecas|
| ||obscurus||North Eastern Sonora, North Western Chihuahua, Southern Arizona|
| ||silus||North East Sonora, South western New Mexico, Western Chihuahua|
| ||willardi||Southern Arizona, Northern Sonora|