Meeting Abstract

51.6  Saturday, Jan. 5  Evolutionary and developmental origins of the maxillary dentition of snakes: Insights from tooth surface morphology JACKSON, K.*; VONK, , F.J.; ADMIRAAL, J.; RICHARDSON, M.K.; Whitman College; Leiden University; Leiden University; Leiden University jacksok@whitman.edu

The Colubroidea is an enormous group of snakes (approx. 2400 species) made up of many lineages, whose branching order is still being questioned by molecular systematists. All venomous species occur within this clade, though the majority are harmless or lie somewhere between �harmless� and �venomous�. This range is reflected by great diversity of the maxillary dentition, including teeth and fangs potentially involved in channeling toxins into bite wounds. This enormously varied maxillary dentition of colubroids has been a focus of interest to systematists since the 1800s. Several attempts have been made to reconstruct the evolutionary history of colubroids based entirely on adult maxillary dentition of the living taxa of this vast clade �none with altogether satisfying results. We examined the maxillary teeth of colubroid snakes using scanning electron microscopy. Using ridges and other tooth surface morphologies as markers, we are able to distinguish between an anterior field of the maxilla, in which tooth morphology is highly conserved, and a posterior field in which great variation in tooth/ fang morphology is seen. We consider the possibility that these two parts of the maxilla are under the control of separate developmental �modules�, and have evolved independently of one another in response to selective pressures. In addition, our observations lend support to hypotheses of a posterior maxillary origin for the front fangs of viperids, elapids, and atractaspidids.