Evolution of the pit vipers

Abstract

The skeleton is one of the most important structures available for the analysis of relationships of vertebrates. This paper assesses relationships within one group of vertebrates, the Crotalidae, by a study of their comparative osteology. The Crotalidae, or pit vipers, of America and Eurasia, is a family of poisonous snakes with movable fangs. The Crotalidae shows remarkable parallel evolution with the Old World family of true vipers, the Viperidae. The Crotalidae differs from the Viperidae in many characters, the most conspicuous of which is the presence of heat-sensitive facial pits. The Crotalidae, as currently defined, includes six genera: Crotalus (rattlesnakes; North, Central, and South America), Sistrurus (pigmy rattlesnakes; North America), Lachesis (bushmaster; Central and northern South America, Trinidad), Bothrops (fer-de-lance, hog-nosed pit vipers, palm pit vipers; Mexico, Central and South America), Trimeresurus (Asiatic pit vipers; southeast Asia), and Agkistrodon (copperheads, moccasins; North America, Asia, and extreme southeastern Europe) .