Notes on the osteology and phylogenetic affinities of the Oligocene Diomedeoididae (Aves, Procellariiformes)
Abstract. New specimens of the procellariiform taxon Diomedeoididae are reported from the early Oligocene (Rupelian) deposits of Wiesloch-Frauenweiler in southern Germany. Two skeletons belong to Diomedeoides brodkorbi, whereas isolated legs of larger individuals are tentatively assigned to D. lipsiensis, a species which has not yet been reported from the locality. The fossils allow the recognition of some previously unknown osteological features of the Diomedeoididae, including the presence of a vestige of the hallux. Diomedeoidids are characterized by extremely wide phalanges of the third and fourth toes, which also occur in some species of the extant procellariiform Oceanitinae (southern storm-petrels). The poorly developed processus supracondylaris dorsalis of the humerus supports a position of these Oligocene tubenoses outside a clade including the Diomedeidae (albatrosses), Procellariidae (shearwaters and allies), and Pelecanoididae (diving-petrels). It is hypothesized that like modern Oceanitinae, which have an equally short supracondylar process, diomedeoidids probably employed flap-gliding and used their immersed feet to remain stationary.