Pseudotoothed birds (Aves, Odontopterygiformes) from the early Tertiary of Morocco. (American Museum novitates, no. 3704)

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American Museum of Natural History.
We describe here new specimens of pseudotoothed birds (Odontopterygiformes) from the Upper Paleocene and Lower Eocene of the Ouled Abdoun Basin, Morocco. These Lower Paleogene fossils are among the oldest representatives of the Odontopterygiformes and include braincases, beak fragments, and long bones. Dasornis toliapica (Owen, 1873) (2-3 m wingspan) and Dasornis emuinus (Bowerbank, 1854) (3.5-4.5 m wingspan) were initially described from the Lower Eocene London Clay of Sheppey, England. The new species Dasornis abdoun (1.5-1.7 m wingspan) constitutes the smallest species of pseudotoothed bird ever discovered. We partly revise the oversplit taxonomy of the odontopterygiforms: the two species from the Paleogene of England and Morocco are regarded as congeneric, the name Dasornis having priority over the name Odontopteryx. We also synonymize Neptuniavis minor Harrison and Walker, 1977, and Macrodontopteryx oweni Harrison and Walker, 1976, with D. toliapica (Owen, 1873). Moreover, the genera Pelagornis Lartet, 1857, and Osteodontornis Howard, 1957, are regarded as pertaining to one single taxonomic entity that corresponds to the Pelagornis morphotype. In Dasornis, the morphological peculiarities of the humerus that are related to gliding flight are less pronounced than in Pelagornis. The latter taxon includes exceedingly specialized gliders that were most likely unable of sustained flapping flight and relied almost entirely on winds to provide lift. Pseudotoothed birds pertaining to the Dasornis morphotype were more generalists and could probably undertake flapping flight, even if limited. The species of Dasornis were soaring pelagic feeders that could disperse over large territories like extant albatrosses. They formed large breeding colonies near the shore of the northeastern part of the Moroccan phosphate sea, some 55 million years ago. Our work provides evidence that Dasornis was widespread in the early Tertiary, as it is currently known from the Lower Paleogene deposits of Morocco, England, and Kazakhstan. Paleoenvironmental studies show that these marine deposits formed in a tropical climate. This could explain the occurrence of both Dasornis and prophaethontids in all three Paleogene localities.
71 p. : ill., map ; 26 cm. "December 20, 2010."
Dasornis., Odontopterygiformes., Morocco., Ouled Abdoun Basin., Birds, Fossil., Tertiary