The development of the pit organ of Bothrops jararaca and Crotalus durissus terrificus (Serpentes, Viperidae): support for the monophyly of the subfamily Crotalinae

The development of the pit organ and the course of the lateral branch of the ethmoidal nerve of the two South American crotalines Bothrops jararaca and Crotalus durissus terrificus are described in detail using serially sectioned material from fetal stages. Serial sections of the Asian pit vipers Agkistrodon halys halys and Trimeresurus albolabris were included in this work. The viperines, as the sister‐group of the Crotalinae, and the Colubridae, Elapidae and Boidae as their outgroups were used for comparisons. New synapomorphies of the advanced subfamily Crotalinae were found: namely, absence of the foramen epiphaniale and an extracapsular course of the lateral branch of ethmoidal nerve. These results support the monophyly of the crotalines.