The dinosaurian femoral head experienced a morphogenetic shift from torsion to growth along the avian stem

Hutchinson, John

Abstract

"The dinosaurian femoral head experienced a cryptic evolutionary shift in morphogenetic process." The evolution of birds-and their highly derived locomotion-from their terrestrial dinosaurian ancestors has captured scientific interest for generations. The transformation of the hip joint from the plesiomorphic saurian condition through intermediate dinosaurian states to that seen in birds is central to this discussion, but developmental and paleontological data imply conflicting and seemingly exclusive hypotheses for how this transition occurred. In this study, we integrated extensive datasets from (1) reptilian embryos using state-of-the-art 3D visualization methods in combination with in vivo embryological tissue tracking, and (2) a phylogenetically extensive sample of fossils showing intermediate character states, to reconstruct an evo-devo scenario for the evolution of the dinosaurian hip. Surprisingly, we found evidence for a cryptic mode of morphological evolution in which underlying developmental mechanisms shifted with resultant adult morphology remaining static. In essence, we found that seemingly similar anatomical structures had highly divergent developmental origins at different places along the avian stem, revealing a complex interplay of morphology, development, and biomechanical constraint. These results, made apparent only by our combination of paleontology and developmental biology, not only provides insights into the evolution of a key dinosaurian/avian innovation but provides a framework for tackling similar complex issues in exploring the evolution of vertebrate form. Our work is of interest to the broad readership of your journal because, building on previous work published in PNAS, Nature, and Science, we integrate data from multiple disciplines to uncover a surprising and complex evolutionary trend across deep time. I appreciate your consideration. I look forward to hearing from you. Sincerely, Shiro EGAWA (江川史朗), Ph.D.

Citation

Hutchinson, J. (2022). The dinosaurian femoral head experienced a morphogenetic shift from torsion to growth along the avian stem. Proceedings of the Royal Society B: Biological Sciences, https://doi.org/10.1098/rspb.2022.0740

• Journal Article Type: Article
• Acceptance Date: Aug 1, 2022
• Online Publication Date: Oct 7, 2022
• Publication Date: Oct 7, 2022
• Deposit Date: Mar 6, 2022
• Publicly Available Date: Oct 10, 2022
• Print ISSN: 0962-8452
• Publisher: The Royal Society
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1098/rspb.2022.0740
• Publisher URL: https://royalsocietypublishing.org/doi/10.1098/rspb.2022.0740