Rattlesnakes are venomous American snakes belonging to the genera Crotalus and Sistrurus. They have retained skin at the end of the tail which make a sharp sound when shaken. Common species include the sidewinder (Crotalus cerastes), the common rattlesnake of the northern United States (C. horridus), the diamond rattlesnake (C. adamanteus) and the western rattlesnake (C. viridis).