Meeting Abstract
138.3 Monday, Jan. 7 Locomotion with constant ventral contact in skinks: a three-dimensional kinematic and dynamic analysis NYAKATURA, J.A.*; CURTH, S.; FISCHER, M.S.; Friedrich-Schiller-University, Jena, Germany john.nyakatura@uni-jena.de
Fossilized tracks attributed to members of the Capthorinidae, a group of fossil early amniotes, imply a constant ventral contact between the animal and the substrate during locomotion. During this ‘belly-walk,’ the trunk is not or only partially lifted off the ground. In extant saurians belly-walking is found in many skinks (Lepidosaurier, Scincidae), rendering them as potential extant models for capthorinidid locomotion. We investigated the biomechanics of locomotion in blue-tongued skinks (Tiliqua scincoides) in order to better understand how propulsion is generated during locomotion in species with constant ventral contact with the substrate. We combined markerless X-ray of moving morphology (XROMM) with the measurement of single limb substrate reaction forces. Biplanar X-ray recordings of two animals during locomotion on a treadmill were taken in order to three-dimensionally analyze locomotor biomechanics over the complete sustainable speed range of the skinks. Subsequently, the skinks were motivated to transverse a trackway instrumented with two 8 x 9 cm custom built force plates. Bone morphology was reconstructed from CT scans of the same individuals. 3D kinematic profiles and single limb substrate reaction force traces are presented. 3D kinematics demonstrate limbs to function according to the double crank system previously described for salamanders. The vertical component of the substrate reaction force is significant enough to substantially reduce frictional forces between the smooth-scaled belly and the substrate. The substrate reaction force vector is used to assess moment arms acting at the elbow, shoulder, knee, and hip joints over time. An additional analysis of the tracks produced by the skinks implies comparable locomotor mechanics in skinks and the fossil Capthorinidae.
