Phylogeny of advanced snakes (Caenophidia)

A partial phylogeny of the Caenophidia indicates the distribution of (1) specialized oral secretory glands (for example, Duvernoy’s glands), (2) specialized dentition, and (3) advanced venom-delivery systems. Because the three-finger toxin (3FTX) peptides are shared among the Elapidae, the Atractaspididae, and the supposedly harmless species Coelognathus radiatus (but not present in the vipers), Fry and his colleagues hypothesized, and subsequently demonstrated, early evolution of the 3FTX toxin family, just after the divergence of the Viperidae. Adapted from Vidal (2002) and Fry (2003b).