Meeting Abstract
The lower jaw is an important proxy of feeding ecology. Transformations in mandibular shape and structure may have facilitated the emergence of different feeding behaviors such as the transition from ram, filter, and rake feeding to suction and protrusion feeding. Here we present an outline and elliptical Fourier analysis of modern and Paleozoic aquatic jawed vertebrates to characterize jaw shape disparity. We achieve this via an exploration of lower jaw morphospace and an evaluation of the functional and ecological consequences of lower jaw shape variation. 95% of shape variation is summarized on seven axes and all component clades of early gnathostomes exhibit overlapping morphological variation to some degree. We find that Modern faunas are more disparate than fossil faunas largely due to variation in extant actinopterygian mandible shape. Our results reject the early burst model of clade evolution and contradict the statement that maximum disparity is reached early in gnathostome evolutionary history. We also find that only some ecological niches that were vacated by fossil taxa have been convergently refilled with living taxa; therefore suggesting the possibility that other factors besides function affect lower jaw morphospace occupation.
