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28 October 2013 More Evidence for Plesiomorphy of the Quadrate in the Eocene Anseriform Avian Genus Presbyornis
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Abstract

Evidence from the quadrate morphology in the American specimens of Presbyornis proved inconsistent with the hypothesis of close relationships of this anseriform genus to modern ducks and geese, but some character states remained uncertain. Here I describe in detail two fairly well preserved Presbyornis quadrates from Central Asia, which provide new evidence for the plesiomorphic, galliform-like morphology of this bone among the anseriforms. Most important, and contrary to a recent report, there is no caudomedial foramen that is present in the extant anseriforms. The only pneumatic foramen is in the basiorbital position, which is plesiomorphic for the galloanserines. At least six other plesiomorphic characters of the quadrate consistently suggest that the Presbyornithidae are stem-group anseriforms.

Copyright © 2014 A. Elzanowski. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Andrzej Elzanowski "More Evidence for Plesiomorphy of the Quadrate in the Eocene Anseriform Avian Genus Presbyornis," Acta Palaeontologica Polonica 59(4), (28 October 2013). https://doi.org/10.4202/app.00027.2013
Received: 17 September 2013; Accepted: 25 October 2013; Published: 28 October 2013
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