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.