Meeting Abstract

P3.59  Tuesday, Jan. 6  Scaling of the appendicular skeleton: CT scan-based analysis of whole-bone geometry for clades Proboscidea and Felidae WIKTOROWICZ CONROY, A*; DOUBE, M; SHEFELBINE, S; HUTCHINSON, JR; The Royal Veterinary College, Structure and Motion Laboratory, University of London awiktorowicz@rvc.ac.uk

Most studies of long bone scaling have focused on external measurements alone, especially for midshaft diameter or circumference and length, and generally have focused on proximal limb elements only, avoiding the metapodials and limb girdles for example. Here we demonstrate a technique using computed tomography (CT) scans to obtain internal and external geometry and quantify scaling of bone geometry throughout the entire bone, for all major bones from the girdles to the metapodials. We examine Proboscidea (elephants), including some data for fossil mammoths and dwarf elephants, to quantify interspecific and intraspecific scaling at giant body size and near-columnar limb posture. We also examine Felidae (cats) to test whether whole-bone geometry changes in order to maintain skeletal stresses across size, as it has been demonstrated that posture does not change markedly with size in this clade. Our results refine and expand on previous studies of these clades, showing that near-isometric scaling predominates within Proboscidea (but weak positive allometry when viewed intraspecifically), versus slight positive allometry within Felidae. Our integrative analysis reinforces the notions that (1) different clades can have quite unique scaling relationships, (2) bone stresses may differentially be maintained by a combination of changes in length, diameter and moments of area, as well as potentially regional bone density, (3) bone strengths or safety factors may be strongly influenced by regions that are weaker than the midshaft.