New methods support the possibility of a salamander-like walk in the Permian tetrapod Eryops

January 3 – Febuary 28, 2021

Meeting Abstract

BSP-11-4  Sun Jan 3 14:45 – 15:00  New methods support the possibility of a salamander-like walk in the Permian tetrapod Eryops Herbst, EC*; Eberhard, E; Manafzadeh, AR; Richards, C; Hutchinson, JR; University of Zurich, Switzerland; EPFL, Lausanne, Switzerland; Brown University, Providence, RI; The Royal Veterinary College, London, UK; The Royal Veterinary College, London, UK

Joint range of motion (ROM) studies help paleontologists constrain locomotor reconstructions. However, no method currently exists to reproducibly integrate ROM data from several limb joints to test whole limb configurations. Here we present a new method for doing so and use it to test whether Eryops megacephalus could adopt a salamander-like gait. We first measured the full ROM of the hip and knee joints of salamander cadavers with only the joint capsule and ligaments intact. We then used scientific rotoscoping to analyze the in vivo ROM used by salamanders during walking. Based on these data, we suggest that in vivo studies offer data for comparisons to fossil taxa that are not available from ex vivo manipulation alone. Therefore, we focused on four limb configurations from the salamander terrestrial stride cycle: toe off, mid swing, toe on, and mid stance. Then, we built a “digital marionette” of Eryops and measured the osteological ROM of its hip and knee. Our new method creates a visual representation of all possible joint poses at each joint of the marionette. We then placed the marionette in each of the four key salamander limb configurations. Our method allowed us to determine that the poses required at both joints to replicate the salamander limb configurations fall within the osteological ROM of Eryops. Based on these results, we conclude that Eryops might have been capable of a salamander-like lateral sequence walking gait. Future studies that incorporate other lines of evidence, such as soft tissue reconstructions and kinetic constraints, will help to further test this hypothesis.

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