Preserved soft anatomy confirms shoulder-powered upstroke of early theropod flyers, reveals enhanced early pygostylian upstroke, and explains early sternum loss

Anatomy of the first flying feathered dinosaurs, modern birds and crocodylians, proposes an ancestral flight system divided between shoulder and chest muscles, before the upstroke muscles migrated beneath the body. This ancestral flight system featured the dorsally positioned deltoids and supracoracoideus controlling the upstroke and the chest-bound pectoralis controlling the downstroke. Preserved soft anatomy is needed to contextualize the origin of the modern flight system, but this has remained elusive. Here we reveal the soft anatomy of the earliest theropod flyers preserved as residual skin chemistry covering the body and delimiting its margins. These data provide preserved soft anatomy that independently validate the ancestral theropod flight system. The heavily constructed shoulder and more weakly constructed chest in the early pygostylian Confuciusornis indicated by a preserved body profile, proposes the first upstroke-enhanced flight stroke. Slender ventral body profiles in the early-diverging birds Archaeopteryx and Anchiornis suggest habitual use of the pectoralis could not maintain the sternum through bone functional adaptations. Increased wing-assisted terrestrial locomotion potentially accelerated sternum loss through higher breathing requirements. Lower expected downstroke requirements in the early thermal soarer Sapeornis could have driven sternum loss through bone functional adaption, possibly encouraged by the higher breathing demands of a Confuciusornis-like upstroke. Both factors are supported by a slender ventral body profile. These data validate the ancestral shoulder/chest flight system and provide insights into novel upstroke-enhanced flight strokes and early sternum loss, filling important gaps in our understanding of the appearance of modern flight.

Medienart:

E-Artikel

Erscheinungsjahr:

2022

Erschienen:

2022

Enthalten in:

Zur Gesamtaufnahme - volume:119

Enthalten in:

Proceedings of the National Academy of Sciences of the United States of America - 119(2022), 47 vom: 22. Nov., Seite e2205476119

Sprache:

Englisch

Beteiligte Personen:

Pittman, Michael [VerfasserIn]
Kaye, Thomas G [VerfasserIn]
Wang, Xiaoli [VerfasserIn]
Zheng, Xiaoting [VerfasserIn]
Dececchi, T Alexander [VerfasserIn]
Hartman, Scott A [VerfasserIn]

Links:

Volltext

Themen:

Early birds
Early flight stroke
Feathered dinosaurs
Flight origins
Journal Article
Preserved soft tissues
Research Support, Non-U.S. Gov't

Anmerkungen:

Date Completed 16.11.2022

Date Revised 18.12.2022

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1073/pnas.2205476119

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM348885490