A confuciusornithiform (Aves, Pygostylia)-like tarsometatarsus from the Early Cretaceous of Siberia and a discussion of the evolution of avian hind limb musculature

ABSTRACT

We describe a new isolated tarsometatarsus from the Early Cretaceous (Barremian-Aptian) Ilek Formation Shestakovo-3 locality in western Siberia. The new specimen represents a new taxon, Evgenavis nobilis, gen. et sp. nov., significantly increasing the Mesozoic avifauna from Russia. The specimen shares morphologies with a number of basal ornithothoracine taxa, but shows most similarity to the basal pygostylian Confuciusornis sanctus, the oldest known beaked bird and most common taxon from the Yixian Formation. Evgenavis may represent the first record of Confuciusornithiformes outside of the Jehol Group and its equivalent deposits. However, this is not supported by cladistic analysis, which weakly resolves the new species and Mystiornis both within the diverse Enantiornithes, indicating that additional material is required to assess the systematic position of Evgenavis nobilis (Aves incertae sedis). The three-dimensional preservation of the specimen allows for a partial reconstruction of the pedal musculature, revealing a primitive stage in the evolution of the neornithine condition.

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ACKNOWLEDGMENTS

We thank Y.-T. Li for preparing the specimen and W. Gao for photography. The specimen was found by S. Ivantsov, a member of 2007 joint expedition to the Shestakovo localities carried out by the Zoological Institute, Tomsk University, and Saint Petersburg University. Excavations at the Shestakovo-3 locality in 2007 were supported by National Geographic Society grant 8268-07. Funding to J.O’C. for this research was provided by the Chinese Academy of Sciences and the Chinese National Science Foundation grant number (KA 21047 and KC 210201). N.V.Z. was supported by the Russian Foundation for Basic Research (grant RFBR 10-04-00575). Research by A.O.A. was supported by the St. Petersburg State University (grant NIR 3.39.148.2011).

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