Meeting Abstract
Squamates compromise the most speciose tetrapod order and move about their environments in many different ways. Evolutionary questions regarding structure-function relationships to allow for fine-branch walking using grip in lizards remain largely unanswered. Fine-branch walking is defined as climbing above and along a relatively thin, horizontal branch. In this part of the study, biomechanical and morphological variables are measured and compared in two pairs of lizard species: each pair are within an infraorder (Iguania and Gekkota) and are composed of a fine-branch specialist and ground generalist with some climbing ability. To understand the biomechanics and make relevant evolutionary comparisons of lizard fine-branch locomotion, each lizard species (n = 4) have been filmed with four high-definition, high-speed cameras while crossing a horizontal, segmented, instrumented beam system (Skywalk) that is able to measure minuscule 3D forces and torques. Two major locomotor modes have been identified: upright walking and belly-dragging. The relatively longer-limbed upright walkers (Specialist Iguanian and Gecko) use grip and produce torques in the fore-aft axis for propulsion and braking and in the left-right axis for balance measured by isolating each limb from a Skywalk segment. The belly-draggers (Generalist Iguanian and Gecko) always touch their belly above the Skywalk beam during locomotion and use their limbs to slide the body along. Recording 3D forces and torques for a single limb in the belly-draggers is difficult, thus comparisons of whole body kinetics were made. Comparisons between and within these groups are helping to shed light on structure-function relationships and evolution of fine-branch walking in lizards and may help with future studies in understanding the origins of grip in tetrapods.
