Sprawling locomotion aspects in a therian mammal 3-Dimensional forelimb kinematics of Tamandua


SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
2021 VIRTUAL ANNUAL MEETING (VAM)
January 3 – Febuary 28, 2021

Meeting Abstract


71-10  Sat Jan 2  Sprawling locomotion aspects in a therian mammal? 3-Dimensional forelimb kinematics of Tamandua Scheidt, A*; Geiger, SM; Wagner, FC; Mülling, CKW; Nyakatura, JA; Institute of Biology, Humboldt University of Berlin, Germany; Institute of Veterinary Anatomy, Histology and Embryology, University of Leipzig, Germany; Institute of Veterinary Anatomy, Histology and Embryology, University of Leipzig, Germany; Institute of Veterinary Anatomy, Histology and Embryology, University of Leipzig, Germany; Institute of Biology, Humboldt University of Berlin, Germany adrianscheidt@gmail.com http://nyakaturalab.com, https://www.vetmed.uni-leipzig.de/veterinaer-anatomisches-institut/

Therian mammals are known to move their forelimbs in a parasagittal plane (elbow pointing caudally) while incorporating retraction of a mobilized scapula during stance phase. In non-cursorial therian mammals the elbow is often abducted, extending out of the parasagittal plane at midstance. This is especially prominent in Tamandua (Xenarthra), which suggests they employ aspects of sprawling locomotion. We test whether Tamandua use amphibian- or lizard-like sprawling forelimb kinematics (i.e., a largely immobile scapula with pronounced lateral spine bending and long-axis rotation of the humerus), resulting in the salient abducted elbow orientation. We use Scientific Rotoscoping, the non-invasive variant of X-ray reconstruction of moving morphology (XROMM) to provide a detailed description of Tamandua forelimb locomotor kinematics during walking and balancing. The results reveal a mosaic of sprawling and parasagittal kinematic characteristics. The abducted elbow is the result of a constantly inward rotated scapula about its long axis and a retracted humerus. Scapula retraction contributes considerably to stride length. However, lateral rotation in the pectoral region of the spine (range: 21°) is higher than reported for other therian mammals, and is similar to skinks and alligators, indicating an aspect generally associated with sprawling locomotion is part of Tamandua forelimb kinematics. Our study contributes to a growing body of evidence of highly variable non-cursorial therian mammal locomotor kinematics.

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