Article: Bony-toothed birds (Aves: Pelagornithidae) from the Middle Eocene of Belgium
Gerald Mayr and Thierry Smith
We describe well-preserved remains of the Pelagornithidae (bony-toothed birds) from the middle Eocene of Belgium, including a sternum, pectoral girdle bones and humeri of a single individual. The specimens are tentatively assigned to Macrodontopteryx oweniHarrison and Walker, 1976, which has so far only been known from the holotype skull and a referred proximal ulna. Another species, about two times larger, is represented by an incomplete humerus and tentatively identified as Dasornis emuinus (Bowerbank, 1854). The fossils provide critical new data on the osteology of the pectoral girdle of bony-toothed birds. For the first time, the sternum of one of the smaller species is preserved, and this bone exhibits a more plesiomorphic morphology than the recently described sternum of the giant Miocene taxon Pelagornis. The coracoid resembles that of the Diomedeidae (albatrosses) in overall morphology, but because bony-toothed birds lack apomorphies of the Procellariiformes, the similarities are almost certainly owing to convergence. Bony-toothed birds were often compared with the 'Pelecaniformes' by previous authors, who especially made comparisons with the Sulidae (gannets and boobies). However, the coracoid distinctly differs from that of extant 'pelecaniform' birds, and the plesiomorphic presence of a foramen nervi supracoracoidei as well as the absence of a well-delimited articulation facet for the furcula supports a position outside the Suloidea, the clade to which the Sulidae belong.