Crotalus cerberus is a venomous pit viper species found in the southwestern United States. It is known as the Arizona black rattlesnake, black rattlesnake, and several other common names. The color pattern consists of a dark grayish, brownish black, reddish brown, or blackish ground color, overlaid with a dorsal pattern of blotches that are rectangular anteriorly, becoming subhexagonal posteriorly, eventually becoming crossbands just before the tail. However, specimens also may be a uniform dark color without any clear dorsal pattern, or the dorsal blotches may be even darker and bordered with white, cream, or yellow transverse rows of scales, or the color pattern may be quite pale with a significant amount of yellow mixed in. A postocular stripe is evident in lightly colored specimens, but not so much in darker ones. (Source: Wikipedia.org, CC BY-SA)