Other Fossils Perhaps Belonging in Dasornis
"Pseudodontornis" longidentata, described from a beak piece and a damaged atlas vertebra of what appears to have been a single individual, is yet another supposed pseudotooth bird species from the Early Eocene London Clay of the Isle of Sheppey. It may well be synonymous with D. emuinus too, or with Macrodontopteryx oweni if that is indeed a distinct species. This also applies to the Lutetian (Middle Eocene) material from Etterbeek (Belgium) which was at first assigned to Argillornis (as was the holotype skull of M. oweni); at least part of the supposed A. longipennis remains – though not its syntype humerus pieces – does seem to be rather small for D. emuinus. Perhaps Gigantornis which is only known from pieces of a sternum found in Middle Eocene rocks in Nigeria also belongs in Dasornis; the sternum of D. emuinus remains unknown, but its size would have been a close match of the Nigerian fossil. Analysis of the unidentified large pelagornithid fossils from the Middle Eocene of Kpogamé-Hahotoé (Togo) which are provisionally termed "Aequornis traversei" might shed light on this issue. The fairly large undescribed remains from the Late Paleocene/Early Eocene of the Ouled Abdoun Basin (Morocco) which have been provisionally termed "Odontopteryx gigas" may in fact be from a small or juvenile Dasornis. The same applies to M. oweni – nonwithstanding that it is sometimes placed in Odontopteryx –, considering it was for long included in Argillornis.
Also provisionally assigned to Argillornis were some pelagornithid wing bone remains, specimens LACM 128462 and presumably also LACM 127875 from the Keasey and Pittsburg Bluff Formations of the Eocene/Oligocene boundary of Oregon. Whether this Pacific species was the same as the Atlantic D. emuinus is undetermined, but considering the age difference it is not all too likely and they may well belong to different genera. In that respect, the enigmatic Cyphornis magnus from the same region is most often assigned a Miocene age, but might actually be from around the Eo-Oligocene boundary as initially assumed; it or (if of Miocene age) an ancestor, or perhaps an ancestor of the Miocene genus Osteodontornis, make a more plausible candidate for the Oregon fossils. Lack of sufficient well-preserved remains have prevented more detailed study however. Similar in size and age to the present genus are some pseudotooth bird remains from Antarctica, namely a jaw piece from the Middle/Late Eocene of the La Meseta Formation of Seymour Island near the Drake Passage, and a Middle Eocene piece of a humerus shaft from Mount Discovery on the continent's Pacific side. Separated from the North Atlantic by a wide distance and the equatorial currents, even in the case of the Seymour Island specimen it is doubtful whether they could be referred to Dasornis, because the fossils are simply too fragmentary.
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