Meeting Abstract

P3.55  Tuesday, Jan. 6  Limb morphology and ground reaction forces in lizards: forelimbs vs. hindlimbs MCELROY, Eric ; College of Charleston mcelroye@cofc.edu

Quadrupeds typically exhibit forelimbs and hindlimbs with different morphologies. These morphological differences are expected to be related to the demands of supporting and propelling the body. For example, running animals exhibit a period of braking force followed by accelerative force which is related to the differential function of fore vs. hind limbs. However, the morphological basis for differential function remains poorly understood. This study explores how morphological differences in the fore- vs. hindlimb are related to differences in individual limb ground reaction forces using a comparative approach. Musculoskeletal limb morphology was quantified for seven species of lizards. In addition, individual limb three-dimensional ground reaction forces (fore- or hindlimb) were quantified for each species as they sprinted down a 3-meter racetrack. Forelimbs exhibited net braking forces whereas hindlimbs exhibited net accelerative force. Surprisingly, lateral forces showed a phylogenetic signal: the four Iguanian had hindlimb-dominated lateral forces whereas lateral forces were roughly equally distributed between fore vs. hindlimbs in the other species. These differences in fore-aft and lateral forces can be explained by the relatively greater length and mass of the hindlimbs in all species, with the greatest difference in the Iguania. Only some species showed differences in vertical forces between the fore- and hindlimbs and these differences were not related to limb morphology, suggesting that other aspects of morphology may influence differences in vertical force (e.g. head vs. tail size).