NDLI: Barb geometry of asymmetrical feathers reveals a transitional morphology in the evolution of avian flight

Content Provider	PubMed Central
Author	Feo, Teresa J. Field, Daniel J. Prum, Richard O.
Copyright Year	2015
Abstract	The geometry of feather barbs (barb length and barb angle) determines feather vane asymmetry and vane rigidity, which are both critical to a feather's aerodynamic performance. Here, we describe the relationship between barb geometry and aerodynamic function across the evolutionary history of asymmetrical flight feathers, from Mesozoic taxa outside of modern avian diversity (Microraptor, Archaeopteryx, Sapeornis, Confuciusornis and the enantiornithine Eopengornis) to an extensive sample of modern birds. Contrary to previous assumptions, we find that barb angle is not related to vane-width asymmetry; instead barb angle varies with vane function, whereas barb length variation determines vane asymmetry. We demonstrate that barb geometry significantly differs among functionally distinct portions of flight feather vanes, and that cutting-edge leading vanes occupy a distinct region of morphospace characterized by small barb angles. This cutting-edge vane morphology is ubiquitous across a phylogenetically and functionally diverse sample of modern birds and Mesozoic stem birds, revealing a fundamental aerodynamic adaptation that has persisted from the Late Jurassic. However, in Mesozoic taxa stemward of Ornithurae and Enantiornithes, trailing vane barb geometry is distinctly different from that of modern birds. In both modern birds and enantiornithines, trailing vanes have larger barb angles than in comparatively stemward taxa like Archaeopteryx, which exhibit small trailing vane barb angles. This discovery reveals a previously unrecognized evolutionary transition in flight feather morphology, which has important implications for the flight capacity of early feathered theropods such as Archaeopteryx and Microraptor. Our findings suggest that the fully modern avian flight feather, and possibly a modern capacity for powered flight, evolved crownward of Confuciusornis, long after the origin of asymmetrical flight feathers, and much later than previously recognized.
Related Links	http://dx.doi.org/10.1098/rspb.2014.2864
Starting Page	20142864
File Format	PDF
ISSN	09628452
e-ISSN	14712954
Journal	Proceedings of the Royal Society B: Biological Sciences
Issue Number	1803
Volume Number	282
Language	English
Publisher	The Royal Society
Publisher Date	2015-02-11
Access Restriction	Open
Rights Holder	The Royal Society
Subject Keyword	Biochemistry, Genetics and Molecular Biology(all) Immunology and Microbiology(all) Agricultural and Biological Sciences(all) Environmental Science(all) Medicine(all) Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Immunology and Microbiology Medicine Biochemistry, Genetics and Molecular Biology Environmental Science Agricultural and Biological Sciences

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