Meeting Abstract
It is generally assumed that great apes share a homologous pattern of torso morphology related to below-branch arboreality that is found in an intermediate state in hylobatids and atelines. This hypothesized variation in torso structure is pivotal to interpretations of fossil ape and hominin body shape and locomotor adaptation. Paleoanthropologists have also presumed that certain morphologies of isolated ribs, vertebrae and pelvis reflect these presumed differences in torso shape and locomotor adaptation. However, little is actually known about the overall 3D shape of the primate torso, or how this is reflected in the morphology of individual bones. To evaluate torso shape, 56 anthropoid cadavers were CT-scanned. In addition, standard landmark and metric data were collected from the pelvis, vertebrae, ribs, and sterna of over 200 primate skeletons. Morphology of the intact torso and that of individual bones were compared across taxa and among locomotor groups, and covariation assessed among skeletal elements and with aspects of whole torso shape. Results broadly support previous hypotheses about basic skeletal variation among taxa for individual bones. 3D reconstruction of intact torsos, though, show more varied and subtle patterns of overall torso shape. Upper thoracic breadth appears to reflect quadrupedality. Iliac morphology reflects as much about axial musculature as about rib cage shape. Strong patterns of allometry are present in the pelvis and in aspects of lumbar vertebral form, but not in rib cage shape. These data support the hypothesis that variation in torso form is associated with locomotion in anthropoids, but reveal nuances of morphological variability that provide much greater insight into the functional consequences that likely have underlain selection for variation in torso structure.
