†P. miocaenus Lartet, 1857
†P. mauretanicus Mourer-Chauviré & Geraads, 2008
†P. chilensis Mayr & Rubilar, 2010
†P. sandersi Ksepka, 2014
and see text
Pelagornis is a widespread genus of prehistoric pseudotooth birds. These were probably rather close relatives of either pelicans and storks, or of waterfowl, and are here placed in the order Odontopterygiformes to account for this uncertainty.[1]
The fossil specimens show that P. miocaenus was one of the larger pseudotooth birds, hardly smaller in size than Osteodontornis or the older Dasornis. Its head must have been about 40 cm (16 in) long in life, and its wingspan was probably more than 5 m (16 ft), perhaps closer to 6 metres (20 ft). Unlike in its contemporary Osteodontornis but like in the older Pseudodontornis, between each two of Pelagornis's large "teeth" was a single smaller one. Pelagornis differed from Dasornis and its smaller contemporary Odontopteryx in having no pneumatic foramen in the fossa pneumotricipitalis of the humerus, a single long latissimus dorsi muscle attachment site on the humerus instead of two distinct segments, and no prominent ligamentum collaterale ventrale attachment knob on the ulna. Further differences between Odontopteryx and Pelagornis are found in the tarsometatarsus: in the latter, it has a deep fossa of the hallux' first metatarsal bone, whereas its middle-toe trochlea is not conspicuously expanded forward. The salt glands inside the eye sockets were extremely large and well-developed in Pelagornis. From the humerus pieces of specimen LACM 127875, found in the Eo-Oligocene Pittsburg Bluff Formation near Mist, Oregon (United States), P. miocaenus differs in an external tuberosity that is not as much extended shoulderwards and that is separated from the elbow end by a wider depression. The head of the humerus is turned more to the inward side and the large protuberance found there is not as far towards the end. The Waipara River humerus mentioned above agrees with P. miocaenus in that respect. If the Oregon fossils are related to Cyphornis and/or Osteodontornis, and if the traits as found in P. miocaenus and the New Zealand specimen are apomorphic, the latter two may indeed be very close relatives.[2]
Four species have been formally described, but several other named taxa of pseudotooth birds might belong in Pelagornis too. The type species Pelagornis miocaenus is known from Aquitanian (Early Miocene) sediments – formerly believed to be of Middle Miocene age – of Armagnac (France). The original specimen on which P. miocaenus was founded was a left humerus almost the size of a human arm. The scientific name – "the most unimaginative name ever applied to a fossil" in the view of Storrs L. Olson[3] – does in no way refer to the bird's startling and at that time unprecedented proportions, and merely means "Miocene pelagic bird". Like many pseudotooth birds, it was initially believed to be related to the albatrosses in the tube-nosed seabirds (Procellariiformes), but subsequently placed in the Pelecaniformes where it was either placed in the cormorant and gannet suborder (Sulae) or united with other pseudotooth birds in a suborder Odontopterygia.[4]
While P. miocaenus was the first pseudotooth bird species to be described scientifically, its congener Pelagornis mauretanicus was only named in 2008. It was a slightly distinct and markedly younger species. Its remains have been found in 2.5 Ma Gelasian (Late Pliocene/Early Pleistocene, MN17) deposits at Ahl al Oughlam (Morocco).[5]