Notes on the osteology and phylogenetic affinities of the Oligocene Diomedeoididae (Aves, Procellariiformes)

The Diomedeoididae are an extinct group of the Procellariiformes (tubenoses), which appears to have been widespread in the epicontinental seas covering parts of Europe in the Oligocene. A fair number of skeletons and isolated bones of these birds are known from Oligocene and early Miocene sediments of Central Europe (Cheneval 1995; Mayr et al. 2002; Fischer 2003). A record from early Oligocene deposits of Iran (Peters & Hamedani 2000) indicates that diomedeoidids were also part of the avifauna of the Paratethyan sea. Diomedeoidids are the only Paleogene procellariiform birds with a substantial fossil record, and three species have been named: the European Diomedeoides brodkorbi (Cheneval, 1995) and D. lipsiensis (Fischer, 1983), which mainly differ in size, and the Iranian D. babaheydariensis (Peters & Hamedani, 2000). The taxonomy of these birds is still in need of a revision, and the taxon name Diomedeoides Fischer, 1985 is likely to be a junior synonym of Rupelornis van Beneden, 1871, which was established for a diomedeoidid species from an early Oligocene locality in Belgium (Mayr et al. 2002). Diomedeoidids are well characterized by their peculiar feet, whose phalanges, in particular those of the fourth toe, are greatly widened and flattened. To a striking extent, the foot morphology of these birds is paralleled by some species of the much smaller extant procellariiform Oceanitinae (southern storm-petrels), i.e., the Polynesian Storm-petrel Nesofregetta fuliginosa (Gmelin, 1789) (Oceanitinae; Mayr et al. 2002: fig. 5) and, to a lesser degree, the species of the taxon Fregetta and the White-faced Storm-petrel Pelagodroma marina (Latham, 1790). The pedal phalanges of other Oceanitinae are of usual proportions, but these have also very long legs as Diomedeoides and other southern storm-petrels. As detailed by Mayr et al. (2002), diomedeoidids lack derived features, which are shared by extant Oceanitinae, and there can be little doubt that the peculiar foot morphology evolved convergently in Diomedeoides and the above storm-petrels. The counter slab of one of the best-preserved skeletons of these birds, from the early Oligocene of southern Germany, was recently donated to Forschungsinstitut Senckenberg. Study of this specimen has allowed phylogenetic affinities and way of living of diomedeoidids to be further examined. This skeleton and other