Evolution of forelimb musculoskeletal function across the fish-to-tetrapod transition

Molnar, JL; Hutchinson, JR; Diogo, R; Clack, JA; Pierce, SE

Abstract

One of the most intriguing questions in vertebrate evolution is how tetrapods gained the ability to walk on land. Although many hypotheses have been proposed, few have been rigorously tested using the fossil record. Here, we build three-dimensional musculoskeletal models of the pectoral appendage in Eusthenopteron, Acanthostega, and Pederpes and quantitatively examine changes in forelimb function across the fin-to-limb transition. Through comparison with extant fishes and tetrapods, we show that early tetrapods share a suite of characters including restricted mobility in humerus long-axis rotation, increased muscular leverage for humeral retraction, but not depression/adduction, and increased mobility in elbow flexion-extension. We infer that the earliest steps in tetrapod forelimb evolution were related to limb-substrate interactions, whereas specializations for weight support appeared later. Together, these results suggest that competing selective pressures for aquatic and terrestrial environments produced a unique, ancestral "early tetrapod" forelimb locomotor mode unlike that of any extant animal.

Citation

Molnar, J., Hutchinson, J., Diogo, R., Clack, J., & Pierce, S. (2021). Evolution of forelimb musculoskeletal function across the fish-to-tetrapod transition. Science Advances, 7(4), https://doi.org/10.1126/sciadv.abd7457

• Journal Article Type: Article
• Acceptance Date: Jan 21, 2021
• Publication Date: 2021
• Deposit Date: Jan 4, 2022
• Publicly Available Date: Jan 4, 2022
• Publisher: American Association for the Advancement of Science
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 4
• DOI: https://doi.org/10.1126/sciadv.abd7457
• Keywords: LIMB; LOCOMOTION; FINS; OSTEICHTHYES; PERSPECTIVES; KINEMATICS; SHOULDER; MOBILITY; SKELETON; ANATOMY
• Public URL: https://rvc-repository.worktribe.com/output/1553854