Meeting Abstract

30.3  Jan. 5  Functional consequences of the loss of the lower temporal bar: a comparative study of bite forces and feeding kinematics in lepidosaurians. SCHAERLAEKEN, V.*; HERREL, A.; ROSS, C.F.; University of Antwerp; University of Antwerp; University of Chicago vicky.schaerlaeken@ua.ac.be

One of the major conundrums in the evolution of vertebrate cranial design is the loss of the lower temporal bar in diapsids. Whereas it has been proposed that the reduction of the lower temporal bar allows for an increase in jaw adductor mass and bite force, this has never been tested experimentally. The skull of Sphenodon punctatus (Rhynchocephalia; tuatara) is different from that of other recent lepidosaurians in being fully diapsid. To test the hypothesis that the loss of the lower temporal bar resulted in an increased bite force we compared bite forces in Sphenodon with data of some basal squamates. Moreover, tuataras are unique in using translation to shear food rather than using the typical puncture-crushing of other lizards. Therefore, we also assessed the efficiency of the feeding system, by recording and comparing cycle durations and number of transport cycles used to transport standardized prey. Sphenodon punctatus had lower bite forces than basal lepidosaurian groups as predicted. Moreover, preliminary kinematic analysis of feeding events suggested a less �efficient� (i.e. requiring more time) prey transport in S. punctatus compared to lizards. Whereas the increased cycle duration is likely due to the increased prominence of the slow closing phase in S. punctatus, the longer feeding bout duration and larger number of transport cycles employed are likely a consequence of the relatively low bite forces in S. punctatus.