Crotalus

Common names: rattlesnakes, rattlers.

Crotalus is a genus of venomous pit vipers found only in the Americas from southern Canada to northern Argentina, colloquially known as rattlesnakes. The name is derived from the Greek word krotalon, which means "rattle" or "castanet", and refers to the rattle on the end of the tail which makes this group (genera Crotalus and Sistrurus) so distinctive. Currently, 32 species are recognized.