We describe a new avian taxon, Itaboravis elaphrocnemoides, gen. et sp. nov., from the late Paleocene fissure fillings of São José de Itaboraí in Brazil. The species is represented by a coracoid and two humeri, which most closely resemble the corresponding elements of the taxon Elaphrocnemus, a proposed stem group representative of the Cariamae from the late Eocene and Oligocene of the Quercy fissure fillings in France. I. elaphrocnemoides is only the second species of small landbird known from the Paleocene of the Southern Hemisphere. It is tentatively classified in the Cariamae, but we also note morphological similarities of the humerus to that of the palaeognathous Tinamidae. We further describe a carpometacarpus, which exhibits a peculiar morphology not found in any other avian taxon. This bone also shares some features with tinamous and is of a size corresponding to that of I. elaphrocnemoides, but cannot be referred to this taxon with confidence. We finally report four morphologically different distal tibiotarsi, one of which may belong to Eutreptodactylus itaboraiensis, the only other small bird described from Itaboraí.

Key words: Aves, Cariamae, Tinamidae, Itaboraí, Itaboravis elaphrocnemoides gen. et sp. nov., Paleocene, Itaboraí, Brazil.

Gerald Mayr [Gerald.Mayr@senckenberg.de], Forschungsinstitut Senckenberg, Sektion Ornithologie, Senckenberganlage 25, D-60325 Frankfurt am Main, Germany; Herculano Alvarenga [halvarenga@uol.com.br], Museu de História Natural de Taubaté, Rua Juvenal Dias de Carvalho 111, CEP 12070-640, Taubaté, SP, Brasil; Julia A. Clarke [Julia_Clarke@jsg.utexas.edu], Department of Geological Sciences, University of Texas at Austin, Austin, TX 78712, USA.