Journal of Ornithology

, Volume 158, Issue 3, pp 859–867 | Cite as

Pectoral girdle morphology of Mesozoic birds and the evolution of the avian supracoracoideus muscle

  • Gerald MayrEmail author
Original Article


The evolution of the avian flight musculature is poorly understood and most studies focused on Archaeopteryx. However, important evolutionary changes occurred within Aves, and here the morphology of the pectoral girdle of Mesozoic birds is interpreted in relation to the evolution of the supracoracoideus muscle, which elevates the wing in the upstroke. In the course of avian evolution, the main origin of this muscle shifted from the coracoid onto the sternum. It is hypothesized that resulting space constraints in the cranial portion of the sternum, which also served as the attachment site for the large pectoralis muscle, led to the evolution of a sternal keel. The cranial portion of the sternum of Early Cretaceous Enantiornithes—one of the major clades of Mesozoic birds—lacks a well-developed keel, and the development of the supracoracoideus muscle must have differed from extant birds. This assumption is in concordance with the fact that a triosseal canal, which forms a pulley for the tendon of this muscle in extant birds, appears not to have been developed in Enantiornithes.


Aves Carina sterni Enantiornithes Flight musculature Ornithuromorpha 


Zur Morphologie des Schultergürtels mesozoischer Vögel und der Evolution des Supracoracoideus-Muskels Die Evolution der Flugmuskulatur der Vögel ist nur unzureichend verstanden und die meisten bisherigen Studien konzentrierten sich auf Archaeopteryx. Wichtige evolutionäre Veränderungen traten allerdings innerhalb der Aves auf, und hier wird die Morphologie des Schultergürtels mesozoischer Vögeln in Bezug auf die Entwicklung des Supracoracoideus-Muskels interpretiert, welcher den Flügel im Aufschlag anhebt. Im Laufe der Vogelevolution verlagerte sich der Hauptursprung dieses Muskels vom Coracoid auf das Sternum. Es wird vermutet, dass daraus resultierende Raumbeschränkungen im kranialen Teil des Sternums, welcher auch als Ansatzstelle für den großen Pectoralis-Muskel diente, zur Entstehung eines Brustbeinkiels führten. Ein gut entwickelter Kiel fehlt dem kranialen Bereich des Brustbeins frühkreidezeitlicher Enantiornithes—einer der Hauptgruppen der mesozoischen Vögel—und der Bau des Supracoracoideus-Muskels der Enantiornithes muss sich von den heutigen Vögeln unterschieden haben. Diese Annahme steht im Einklang mit der Tatsache, dass ein triossealer Kanal, welcher die Sehne des Supracoracoideus-Muskels bei den heutigen Vögeln umlenkt, bei den Enantiornithes nicht entwickelt war.



I thank Andrzej Elzanowski and two anonymous reviewers, whose comments improved the manuscript.


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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2017

Authors and Affiliations

  1. 1.Ornithological SectionSenckenberg Research Institute and Natural History Museum FrankfurtFrankfurt am MainGermany

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