The ability to efficiently move over uneven terrain is critical for most terrestrial animals. Bipedal running is common in lizard species, however the biological advantage of a bipedal running posture remains uncertain. I examined the hypothesis that a bipedal posture is advantageous when crossing obstacles. Particularly, I determined whether kinematic adjustments differ among four focal species with contrasting body forms and ecology. I also examined how sprint speed changed when crossing obstacles with a quadrupedal versus a bipedal posture. I quantified kinematics from high-speed video (300 frames/second) of lizards running down a 3m runway both with and without the presence of an obstacle. Among species, I observed high variation in kinematics, locomotor performance and behavior when crossing obstacles. Within species, mean forward speed (velocity) and kinematics did not change between treatments when employing a bipedal posture. However among species, kinematics differed when using a bipedal posture indicating morphological variation influences how a species utilizes a bipedal posture. Overall, my study suggests an advantage in a bipedal posture when faced with obstacles
