Meeting Abstract
Crocodylians are the sole surviving lineage of archosaurs that retain a generalized, quadrupedal body plan. As such, data on crocodylian locomotor biomechanics can provide a useful context for understanding the ontogeny and evolution of functional performance in this formerly diverse lineage. Previous studies of subadult American alligators (2–4 kg) suggested that the hindlimbs play dominant roles in weight support and propulsion during terrestrial locomotion. Since morphological data indicate that the center of mass shifts anteriorly throughout growth, we predict smaller alligators will show even greater dominance of the hindlimbs on land. We tested this prediction by measuring ground reaction forces of juvenile alligators (220–240 g) during single-limb footfalls on a force platform, as they walked through a trackway at their natural speeds. Force data show that forelimbs of juvenile alligators contribute an even larger role in weight support and braking than in subadults. The mean peak vertical force and impulse for the forelimbs during stance are as much as one-third greater than of those of the hindlimbs. Peak braking force and braking impulse are also much greater in the forelimbs than the hindlimbs for juvenile alligators, whereas peak propulsive and medial forces and impulses are greater in hindlimbs. The greater role of the forelimb in body support in juvenile alligators does not match predictions based on ontogenetic morphological changes. This could imply that at very small sizes, alligators can use kinematics that release them from constraints expected from their body mass distribution. Alternatively, ontogenetic shifts in the position of the center of mass may follow a non-linear trend such that juvenile alligators do not match the predictions of linear models.
