Crotalus viridis nuntius
San Juan Co., Utah. May 29, 2011.
At the time I saw this snake, nuntius had been sunk, and was considered a local variant of the prairie rattler. Thanks to Davis et al. 2016, the Hopi rattlesnake is back, as a subspecies of Crotalus viridus. See: Davis MA, Douglas MR, Collyer ML, Douglas ME 2016. Deconstructing a Species-Complex: Geometric Morphometric and Molecular Analyses Define Species in the Western Rattlesnake (Crotalus viridis). PLoS One 11 (1): e0146166.doi:10.1371/journal.pone.0146166
Colorado 2011 Flickr album is here.
HerpMapper records for this species are here.