36 - Limb Kinetics in the Central Bearded Dragon, a Terrestrial Lizard Closely Related to Chameleons

Poster Board Number: 36
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Abstract Body : Locomotion is an integral factor in the survival and fitness of a speciesLizards are a group of reptiles that are capable of a wide range of locomotor behaviors, including climbing, swimming, and bipedal running. However, few studies have measured limb kinetics in lizards to understand normal loading conditions in sprawling tetrapodsThe Central bearded dragon (Pogona vitticeps) is a terrestrial, quadrupedal lizard closely related to chameleons, a family of highly arboreal lizards with unusual locomotion.. This study was performed to determine the direction and magnitude of the forces generated by the forelimbs and hindlimbs in bearded dragons and thus expand our knowledge of the limb kinetics in quadrupeds broadly.
Four bearded dragons ran across a track consisting of a long piece of plywood with an inconspicuous force plate in the middle to capture generated forces. The setup also consisted of three different high speed video cameras which were angled in three different fields to better understand the kinematics involved in the forelimbs and hindlimbs. After each trial, the videos were analyzed to confirm successful hits and force data (anterior-posterior, mediolateral, and vertical) was obtained using a custom script in MATLAB. Each bearded dragon had at least 10 successful trials for their forelimbs and hindlimbs. In both forelimb and hindlimb, peak forces were greatest in the vertical direction, indicating support of body weight. Vertical peak forces were greater in the forelimb,suggesting that the center of mass is located more cranially than it is in varanids, for the latter whose peak vertical forces are greater in the hindlimb. Typical of animals that use sprawling posture, lateral forces were more than twice as high as medial forces. Posteriorly directed forces were greater in the hindlimb while braking forces were significantly greater in the forelimb, indicating that the hindlimb provides most of the propulsive force.
Our results indicate that the limb kinetics in Central bearded dragons are similar to those of other terrestrial lizards such as varanids. Therefore, the characteristic limb mechanics of chameleons, with extremely low mediolateral forces and a mainly propulsive forelimb, were most likely acquired within the family Chamaeleonidae from an ancestor whose limb function resembled that of extant terrestrial, sprawling lizards. Further analysis of our results needs to be performed to determine the kinematics and spatiotemporal characteristics of the Pogona vitticeps. Results of kinematic data can then be further compared to a phylogenetically broad and ecologically diverse range of lizards such as varanids, anoles, geckoes, and chameleons so that a better picture of the locomotor evolution of this group can be drawn.