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Link to original content: https://pubmed.ncbi.nlm.nih.gov/35687000
Multi-Joint Analysis of Pose Viability Supports the Possibility of Salamander-Like Hindlimb Configurations in the Permian Tetrapod Eryops megacephalus - PubMed Skip to main page content
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. 2022 Aug 25;62(2):139-151.
doi: 10.1093/icb/icac083.

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

Eva C Herbst  1   2 , Armita R Manafzadeh  3 , John R Hutchinson  2
Affiliations

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

Eva C Herbst et al. Integr Comp Biol. .

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.

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Figures

Fig. 1
Fig. 1
Eryops megacephalus photogrammetry models, scaled to fit limb proportions of a single individual. Pelvis FMNH UC 446 in (A) right lateral and (B) left lateral views. (C) Right femur FMNH UC 33 in a lateral view; (D) right fibula FMNH UC 203 in a lateral view; (E) right tibia FMNH UC 1250 in a lateral view; (F) right tibia FMNH UC 1250 in a medial view; (G) right fibula FMNH UC 203 in a medial view; and (H) right femur FMNH UC 33 in a medial view. Scale bar = 10 cm.
Fig. 2
Fig. 2
Eryops megacephalus right hip joint in an (A) anterior view and (B) lateral view, with right acetabular ACS and right proximal femur ACS in null pose (with femur laterally extended). The proximal femur ACS was translated slightly laterally and dorsally to account for cartilage and to prevent the femur intersecting with the ventral acetabular rim (translation values discussed in text). The animation joint in Maya was positioned mid-way between the two ACS origins with a point constraint, and the axes of the joint were aligned with the axes of the ACSs in null pose with an orient constraint. (C and D) Salamandra salamandra hip joint in anterior and lateral views. The Z-axis (FE, blue) points ventrally, the Y-axis (ABAD, green) points posteriorly, and the X-axis (LAR, red) points laterally. Not to scale.
Fig. 3
Fig. 3
Eryops megacephalus right knee joint in anterior view, flexed (rotated about Z) at 45 degrees from the null pose (in which the proximal tibia/fibula ACS is aligned with the distal femoral ACS). (A) Knee spacing option A (tight joint spacing); (B) knee spacing option B (intermediate joint spacing); and (C) knee spacing option C (large joint spacing, based on the same relative joint spacing as in S. salamandrain the null pose).
Fig. 4
Fig. 4
Hindlimb configurations in S. salamandra(A) from rotoscoping of in vivo walking, during (B) mid-swing, (C) toe-on, (D) mid-stance, and (E) just before toe-off. These limb configurations were recreated in E. megacephalus(F) with three different knee spacing options: (G–J) tight knee spacing; (K–N) intermediate knee spacing; and (O–R) larger knee spacing, based on the amount of knee spacing present in the rotoscoped salamander at the null pose. Salamandra salamandra configurations in (B–E) were scaled to E. megacephalus knee B.
Fig. 5
Fig. 5
Alpha shapes illustrating osteological RoM for the E. megacephalus hip (A and B) and knee (C–H) joints. (C and D) Knee spacing option A (tight spacing); (E and F) knee spacing option B (intermediate spacing); and (G and H) knee spacing option C (large spacing, same relative joint spacing as salamander in null pose). Salamander joint poses used during key phases of the walking stride cycle are depicted as circles, replicated poses in E. megacephalus are depicted as triangles. Purple: mid-swing, blue: toe-on, green: mid-stance, and yellow: just before toe-off.
Fig. 6
Fig. 6
Hindlimb pose just before toe-off for S. salamandra(A,B) and E. megacephalus(C-F) in lateral (A, C, and E) and posterior (B, D, and F) views of the hip joint. C and D show the version of the E. megacephalus hindlimb from Fig. 4 (with intermediate knee joint spacing option), with the limb bones aligned as closely as possible to those of S. salamandra. E and F show an alternative just before toe-off pose for E. megacephalus, with less internal rotation of the hip, resulting in a hip joint where the proximal femoral surface is more aligned with the acetabular shape.
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