PATTERNS OF GROWTH OF THE MANDIBULAR CORPUS IN SPOTTED HYENAS (CROCUTA-CROCUTA) AND COUGARS (PUMA CONCOLOR)

Differences in jaw morphology among adult carnivorans are well establi shed, but the ontogenetic mechanisms by which these differences arise are largely unexplored. Mandibular ontogeny in Crocuta crocuta and Pum a concolor is analysed biomechanically using principles of beam theory . In each species, the development of cross-sectional properties of th e mandibular corpus associated with rigidity under loading follows a b iphasic pattern of growth. In early postnatal growth, deposition of co rtical bone appears to be constrained by the overall weaker tissue wit h which juvenile skeletons are constructed and by the need to volumetr ically accommodate the developing teeth within their bony crypts. Thus , this stage of growth is characterized by a net periosteal deposition of bone and a swelling of the medullary cavity. In late postnatal gro wth, the constraints on endosteal deposition of bone are relieved as t he permanent teeth erupt; thus, cortical thicknesses increase sharply by periosteal expansion as well as medullary contraction. Finally, it is noted that basic differences in jaw construction between Crocuta an d Puma appear to develop prenatally as they are largely in place at bi rth. Hence, postnatal development enhances, but does not soley contrib ute to, the biomechanical differences in the jaws of these species. (C ) 1997 The Linnean Society or London.