SCHWENK, K.; GIGNAC, P.M.*; University of Connecticut; Florida State University: The anatomical basis of cranial kinesis in lizards

A number of studies have focused on the form and function of intracranial movements in lizards (cranial kinesis), but rarely has the anatomy and potential movement of individual joints been evaluated. Frazetta (1983) suggested that cranial kinesis is an adaptation for precise and simultaneous contact of upper and lower jaws during prey capture. According to Schwenk (2000), cranial kinesis should therefore be restricted to lizards employing jaw-prehension (Scleroglossa) and absent in lingual feeders (Iguania). Limited functional observations are consistent with this hypothesis. We studied the microscopic anatomy of the kinetic joints in iguanian and scleroglossan lizards and found that all five intracranial joints we examined were capable of movement in scleroglossan lizards, but only two of five joints showed potential for kinesis in iguanian species. Although more species need to be sampled, these data offer preliminary support to the Frazzetta and Schwenk hypotheses.