Comparative three-dimensional kinematics of the hindlimb for high-speed bipedal and quadrupedal locomotion of lizards

TLDR

Lizards are widely used in locomotor research, yet their limb movements during high‑speed locomotion remain poorly understood. The study aimed to quantify the three‑dimensional kinematics of hindlimb, body, and tail in five morphologically distinct lizard species during near‑maximum sprinting speeds. Using 3‑D motion capture, the authors measured hindlimb, body, and tail kinematics of the five species while running at 2–5 m s⁻¹. Kinematic analyses revealed species‑specific patterns: digitigrade foot posture was common but varied, large foot size and digitigrade posture elevated hip height, distinct kinematic suites separated bipedal from quadrupedal strides, and all species exhibited high Froude numbers and stride lengths compared with other vertebrates.

Abstract

ABSTRACT Although lizards have been model organisms for testing locomotor performance and in ecomorphological studies, the limb movements of lizards during high-speed locomotion are poorly understood. Thus, we quantified the three-dimensional kinematics of the hindlimb, body and tail for five morphologically distinct species of lizard during steady-speed locomotion near maximum sprinting speed (2–5 m s−1 ). The kinematics of different species had little multivariate overlap. More than half of the strides of all species had digitigrade foot posture, but the frequency of using digitigrade foot posture varied among species. The combination of digitigrade foot posture and large foot size of the lizards contributed substantially to the high values of hip height. For each species, different suites of kinematic variables distinguished bipedal from quadrupedal strides. Interspecific morphological variation did not correspond globally to variation in kinematics, although lizard species with elongated hindlimbs took longer strides than species with shorter hindlimbs. The Froude numbers and relative stride lengths of all lizards running near maximal speeds were large compared with those reported previously for other vertebrates.