Discovery of a Dicephalic Western Diamondback Rattlesnake, Crotalus atrox (Serpentes: Viperidae), from Texas, with a Summary of Dicephalism Among Members of the Genus Crotalus

We document the fourth record of a dicephalic western diamondback rattlesnake, Crotalus atrox, collected on 17 September 2005 in Tom Green County, Texas, along with features of its external and internal anatomy, which are compared with normal C. atrox neonates. This is only the second reported case of complete anatomical duplication of the respiratory system and nearly complete duplication of the circulatory and digestive systems in dicephalic snakes. In addition, we present a summary of dicephalism among 10 species within the genus Crotalus