Multi-Joint Analysis of Pose Viability Supports the Possibility of Salamander-Like Hindlimb Configurations in the Permian TetrapodEryops megacephalus

Abstract

Salamanders are often used as analogs for early tetrapods in paleontological reconstructions of locomotion. However, concerns have been raised about whether this comparison is justifiable, necessitating comparisons of a broader range of early tetrapods with salamanders. Here we test whether the osteological morphology of the hindlimb in the early tetrapod (temnospondyl amphibian) Eryops megacephalus could have facilitated the sequence of limb configurations used by salamanders during terrestrial locomotion. To do so, we present a new method that enables the examination of full limb configurations rather than isolated joint poses. Based on this analysis, we conclude that E. megacephalus may indeed have been capable of salamander-like hindlimb kinematics. Our method facilitates the holistic visual comparison of limb configurations between taxa without reliance on the homology of coordinate system definitions, and can thus be applied to facilitate various comparisons between extinct and extant taxa, spanning the diversity of locomotion both past and present.

In vivo and ex vivo range of motion in the fire salamander Salamandra salamandra

“…Further studies are needed to determine whether this is a consistent trend, or due to inter‐individual variation. Knee in vivo ABAD and LAR were a subset of ex vivo poses, meaning that in these rotational axes, the joints operate well within their limits during walking. In the knee, some similar patterns were observed in vivo and ex vivo: in all specimens, FE was the greatest range, and within an individual, ABAD and LAR ranges were similar. Interactions of degrees of freedom are important; maximum and minimum joint rotations were rarely reached close to the null pose. Aim 3 : The pose space of S. salamandra knee and hip joints reported here can be used in future studies as a reference dataset comparing fossil RoM to joint RoM in S. salamandra . This dataset was used (Herbst, Manafzadeh, & Hutchinson, 2022) to investigate whether salamander‐like hindlimb kinematics were possible in the early tetrapod Eryops .…”

“… Aim 3 : The pose space of S. salamandra knee and hip joints reported here can be used in future studies as a reference dataset comparing fossil RoM to joint RoM in S. salamandra . This dataset was used (Herbst, Manafzadeh, & Hutchinson, 2022 ) to investigate whether salamander‐like hindlimb kinematics were possible in the early tetrapod Eryops . …”

“…The results of our study on salamander hind limb joint RoM can be used to determine what joint poses are used in a typical salamander‐like walk. In Herbst, Manafzadeh, and Hutchinson ( 2022 ), we use this data to investigate the possibility of salamander‐like hindlimb configurations in the early tetrapod Eryops .…”

Modern three-dimensional digital methods for studying locomotor biomechanics in tetrapods

“…1 B) not only in extant taxa but also in extinct ones ( Pierce et al, 2012 ; Nyakatura et al, 2015 ; Manafzadeh and Padian, 2018 ; Demuth et al, 2020 ; Richards et al, 2021 ; Herbst et al, 2022c ; Wiseman et al, 2022b ) where, unlike in extant animals, the joint movement cannot directly be observed or otherwise estimated. The osteological range of motion (ROM) is influenced by the thickness of articular cartilage (permitting more or less motion depending on joint spacing), and by the accuracy of the joint centre position estimation ( Demuth et al, 2020 ; Herbst et al, 2022c ; Wiseman et al, 2022b ). Because of the complex interplay of different DOF during motion ( Kambic et al, 2014 ; 2017 ), single-axis estimates have been deemed unreliable and multi-axis mobility needs to be assessed ( Manafzadeh and Padian, 2018 ).…”

The functional significance of aberrant cervical counts in sloths: insights from automated exhaustive analysis of cervical range of motion

“…Automated approaches to quantify interacting movements in the less osteologically constrained articulations of the appendicular skeleton, e.g. limb joints, have recently been developed [13,[27][28][29][30][31][32]. Here, we developed this methodology further and employed an automated three-dimensional assessment of intervertebral ROM specifically accounting for interacting rotations of roll, yaw and pitch occurring in the cervical column, using criteria based on both bone-bone collisions and disarticulation.…”