Convergent evolution of quadrupedality in ornithischian dinosaurs was achieved through disparate forelimb muscle mechanics.

Content Provider	Europe PMC
Author	Dempsey, Matthew Maidment, Susannah C. R. Hedrick, Brandon P. Bates, Karl T.
Copyright Year	2023
Abstract	The secondary evolution of quadrupedality from bipedal ancestry is a rare evolutionary transition in tetrapods yet occurred convergently at least three times within ornithischian dinosaurs. Despite convergently evolving quadrupedal gait, ornithischians exhibited variable anatomy, particularly in the forelimbs, which underwent a major functional change from assisting in foraging and feeding in bipeds to becoming principal weight-bearing components of the locomotor system in quadrupeds. Here, we use three-dimensional multi-body dynamics models to demonstrate quantitatively that different quadrupedal ornithischian clades evolved distinct forelimb musculature, particularly around the shoulder. We find that major differences in glenohumeral abduction–adduction and long axis rotation muscle leverages were key drivers of mechanical disparity, thereby refuting previous hypotheses about functional convergence in major clades. Elbow muscle leverages were also disparate across the major ornithischian lineages, although high elbow extension muscle leverages were convergent between most quadrupeds. Unlike in ornithischian hind limbs, where differences are more closely tied to functional similarity than phylogenetic relatedness, mechanical disparity in ornithischian forelimbs appears to have been shaped primarily by phylogenetic constraints. Differences in ancestral bipedal taxa within each clade may have resulted in disparate ecomorphological constraints on the evolutionary pathways driving divergence in their quadrupedal descendants.
ISSN	09628452
Journal	Proceedings of the Royal Society B: Biological Sciences
Volume Number	290
PubMed Central reference number	PMC9890092
Issue Number	1992
PubMed reference number	36722082
e-ISSN	14712954
DOI	10.1098/rspb.2022.2435
Language	English
Publisher	The Royal Society
Publisher Date	2023-02-01
Access Restriction	Open
Rights License	Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. © 2023 The Authors.
Subject Keyword	macroevolution biomechanics multi-body dynamics dinosaurs quadrupedality moment arms
Content Type	Text
Resource Type	Article
Subject	Immunology and Microbiology Medicine Biochemistry, Genetics and Molecular Biology Environmental Science Agricultural and Biological Sciences