Science Outreach Athabasca

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Science Outreach – Athabasca presents…
Attachment scars of uncinate processes indicate an early origin of avian-like breathing mechanism in dinosaurs.
Speaker: Yan-yin Wang
PhD candidate, Sullivan Lab, University of Alberta
Date: Tuesday, January 25, 2022
Time: 7 PM
Please join the virtual session below:…
Meeting ID: 841 1632 2871
Passcode: 108379
Birds and crocodilians are modern representatives of Archosauria, a group of amniotes originated in Triassic and filled most of the ecological niches available for large-bodied animals (e.g. non-avian dinosaurs) throughout Jurassic and Cretaceous. Dorsal ribs of archosaurs often carry unciantes, often called uncinate processes on the their tail side in the form of ossified hooks in birds, and in the form of cartilaginous tabs in crocodilians. Muscles associated with unciantes have received experimental support on respiratory functions in Canada geese and American alligators. To better understand how uncinates assist respirations mechanically, we constructed a musculoskeletal model of paleognaths, a group of terrestrial birds, to examine the mechanical advantages brought by the presence of unciantes. Our initial results agree with experimental studies on Canada geese and American alligators that uncinates improve the performance of their associated respiratory muscles. Uncinates and uncinate-like structures are known in several groups of fossil dinosaurs where the unciantes are ossified as in birds, or the cartilaginous elements were lucky enough to be preserved, which raise the potential that unciantes and their respiratory functions may be an ancestral condition inherited by modern birds and crocodilians. Unfortunately, cartilaginous elements are found less frequently in the fossil records, which makes direct observations of unciantes less feasible. Instead, we established a proxy on the dorsal ribs called uncinate scars, to infer the presence of unciante when these structures are not preserved using surface features as well as microscopic features. The distribution of the uncinate scars, and by extension unciantes, suggest that uncinate-assisted respirations as in birds likely have appeared already at the dawn of Archosauria.
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