sidewinder, common name for a rattlesnake, Crotalus cerastes, found in the deserts of the SW United States. This 2-ft (60-cm), pale yellow and pink snake is named for its curious method of locomotion. It throws out successive loops at oblique angles, which gives it the appearance of moving sideways. This mode of progression, also evolved by certain African desert snakes, enables it to move over sand, which offers little traction. The sidewinder has prominent, erect scales above its eyes and is sometimes known as the horned rattlesnake. During the heat of the day it lies half buried in the sand; it hunts small animals in the evening. The sidewinder is classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Squamata, family Crotalidae.