Meeting Abstract

88.3  Sunday, Jan. 6   Joint contributions to locomotor velocity and power in Iguana iguana ALLEN, V*; NYAKATURA, J; Univ.of Jena; Univ.of Jena mrvivianallen@gmail.com

In ‘Sprawling’ locomotion (e.g. lizards and salamanders), 3D limb kinematics appear more important than the more planar motions of ‘upright’ animals. In particular, due to the highly abducted proximal limb segment forward motion can be achieved both by its retraction and long-axis rotation (LAR) – the ‘double-crank’ mechanism. This is observed in both pectoral and pelvic limbs of salamanders, but it’s significance in lizards and other ‘sprawlers’ is not fully known. Here, we use simultaneous measurement of 3D kinematics (XROMM) and limb endpoint forces in a representative lizard (Iguana iguana) to quantify joint rotations, torques, powers, and contributions to overall body velocity. In support of previous hypotheses, we find that the importance of the ‘double crank’ to locomotor progression is much greater in the pectoral than the pelvic limb of I. iguana. However, rather than a simple ‘double crank’, we find complex patterns of 3D pectoral girdle, shoulder and elbow rotations all contribute to forward velocity and power at different points during stance. In contrast, progressive power in the pelvic limb is provided mainly by planar flexion and adduction at the hip and carpal joints – while significant non-planar torques and rotations are found, these appear to be associated with braking and control of ground reaction torques rather than progression. Detailed 3D kinematics for sprawling animals are only recently available via the XROMM method, and so the distribution of such differential mechanisms of pectoral/pelvic limb progression cannot yet be assessed across Lepidosauria. It is possible that this represents a similar fore/hind support/power differentiation to that seen in mammals, although by acting as a ‘wheel’ rather than a ‘strut’, the forelimb may be better able to also provide locomotor power.