HINDLIMB KINEMATICS DURING TERRESTRIAL LOCOMOTION IN A SALAMANDER (DICAMPTODON TENEBROSUS)

Abstract

A quantitative study of hindlimb kinematics during terrestrial locomotion in a non-specialized salamander was undertaken to allow comparisons with limb movements in other groups of tetrapods. Five Dicamptodon tenebrosus were videotaped at 200 fields s-1 walking on a treadmill. Coordinates of marker points on the salamander's midline, pelvic girdle and left hindlimb were digitized through at least three strides at both a walk (0.77 SVL s-1, where SVL is snout­vent length) and a trot (2.90 SVL s-1). Marker coordinates were used to compute kinematic variables summarizing trunk flexion, pelvic girdle rotation, femoral protraction/retraction and knee flexion/extension. The stride is characterized by uninterrupted trunk and pelvic girdle oscillation, femoral retraction throughout stance phase, and knee flexion in early stance followed by extension. Mean angular excursions are: trunk, 66 °; pelvic girdle, 38.5 °; pelvic girdle­femur, 106 °; and knee, 65 °. The hindlimb and pelvic girdle also show a complicated pattern of lateral movement related to knee flexion/extension and periods of support by the contralateral hindlimb during the step cycle. Dicamptodon shares the following features of the hindlimb step cycle with other tetrapod taxa: rotation of the pelvic girdle through a 30­40 ° arc, femoral retraction beginning simultaneously with and persisting throughout stance phase, flexion of the knee in early stance, and extension of the knee in late stance.