Prey processing in amniotes: biomechanical and behavioral patterns of foodreduction

In this paper we examine the biomechanics of prey processing behavior in th e amniotes. Whether amniotes swallow grey items whole or swallow highly pro cessed slurries or boluses of food, they share a common biomechanical syste m where hard surfaces (teeth or beaks) are brought together on articulated jaws by the actions of adductor muscles to grasp and process food. How have amniotes modified this basic system to increase the chewing efficiency of the system? To address this question we first examine the primitive conditi on for prey processing representative of many of the past and present preda tory amniotes. Because herbivory is expected to be related to improved prey processing in the jaws we review patterns of food processing mechanics in past and present herbivores. Herbivory has appeared numerous times in amnio tes and several solutions to the task of chewing plant matter have appeared . Birds have abandoned jaw chewing in favor of a new way to chew - with the gut - so we will detour from the jaws to examine the appearance of gut che wing in the archosaurs. We will then fill in the gaps among amniote taxa wi th a look at some new data on patterns of prey processing behavior and jaw mechanics in lizards. Finally, we examine evolutionary patterns of amniote feeding mechanism and how correlates of chewing relate to the need to incre ase the efficiency of prey processing in order to facilitate increased meta bolic rate and activity. (C) 2000 Elsevier Science Inc. All rights reserved .