Meeting Abstract

P1-66   -   Effects of locomotion on external and internal forelimb structure in Sciuridae Rickman, J*; Burtner , A; McFeely, A; Santana, S E; Law, C J; University of Washington; University of Washington; University of Washington; University of Washington; University of Washington jrickman@uw.edu

In vertebrates, differences in limb morphology are often the result of adaptions to locomotion. While previous researchers have examined the external shape of skeletal elements, there have been relatively fewer studies examining internal bone structure despite its potential significance to locomotor biomechanics and function. This study aims to help fill this gap by quantifying external and internal differences in forelimb skeletal morphology across species spanning various locomotor ecologies in the family Sciuridae (squirrels). Squirrels can be classified into three distinct ecotypes (ground, tree, and gliding) based upon differences in morphology, locomotion, and life history; we test the hypothesis that forelimb skeletal morphology reflects adaptations to these niches. Specifically, we predict that gliders will have relatively longer, more gracile, and less compact bones due to the gravitational/aerodynamic constraints of gliding whereas ground squirrels will exhibit more robust, highly compact long bones to gain more force while digging burrows​​. To test these predictions, we CT scanned the humerus and ulna from 46 species of squirrels, used 3D geometric morphometrics to assess differences in the external shape, and conducted bone structure analyses to assess differences in the cortical and trabecular bone. Preliminary results support previous findings and our prediction that gliding squirrels exhibit relatively longer bones, tree squirrels exhibit intermediate length bones, and ground squirrels exhibit relatively shorter forelimbs. This research furthers the understanding of diversity in forelimb morphology across mammals and the connection between forelimb morphology and locomotion.