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 23 MA
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 – 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. 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). Additional
fossils are placed in
Pelagornis, usually without assignment to species, mainly due to their large size and Miocene age. From the United States, such specimens have been found in the Middle Miocene
Calvert Formation of
Maryland and
Virginia, and the contemporary
Pungo River Formation of the
Lee Creek Mine in
North Carolina (though at least one other pelagornithid is probably represented among this material too).
USNM 244174 (a
tarsometatarsus fragment) was found near
Charleston, South Carolina and assigned to
P. miocaenus, and the slightly smaller left tarsometatarsal middle
trochlea USNM 476044 might also belong here. A broken but fairly complete
sternum probably of this genus, specimen
LHNB (CC-CP)-1, is known from the
Serravallian-
Tortonian boundary (Middle to
Late Miocene) near
Costa da Caparica in
Portugal. Contemporary are certain specimens from the
Bahía Inglesa Formation of
Chile, while other material from this formation as well as remains from the
Pisco Formation of Peru are from the Late Miocene to
Early Pliocene. It is not clear whether the
South American fossils – of similar size and age and not including directly comparable bones – are from one or two species. A very worn sternum and some other remains from the Miocene of
Oregon as well as roughly contemporary material from
California are sometimes assigned to
Pelagornis, but this appears to be an error; if not of the contemporary
North Pacific Osteodontornis, the specimen is better regarded as indeterminable. Given the distance in space and time involved, all
Pacific material may well have been a species different from
P. miocaenus or even from birds closer to
Osteodontornis. Indeed, some of the older Bahía Inglesa Formation remains tentatively referred to
Pelagornis were at first assigned to the mysterious
Pseudodontornis longirostris in error, and a
proximal (initially misidentified as
distal) humerus piece (
CMNZ AV 24,960), from the
Waiauan (Middle-Late Miocene) cliffs near the mouth of the
Waipara River (
North Canterbury, New Zealand) seems to differ little from either
O. orri or
P. miocaenus. The Pisco Formation specimens – which may be from the same species as the Bahía Inglesa ones, or from its direct descendant – on the other hand seem to be well distinct from
Osteodontornis. It must be remembered, however, that the
Isthmus of Panama had not been formed yet during the Miocene.
Pelagornis sandersi, whose fossil remains date from 25 million years ago during the
Chattian age of the
Oligocene, was described in July 2014,. The only known fossil of
P. sandersi was first uncovered in 1983 at
Charleston International Airport,
South Carolina, discovered by James Malcom, while working construction building a new terminal there. At the time the bird lived, 25 million years ago, global temperatures were higher, and the area where it was discovered was an ocean. After excavation, the fossil of
P. sandersi was catalogued and put in storage at the
Charleston Museum, where it remained until it was rediscovered by
paleontologist Daniel T. Ksepka in 2010. The bird is named after Albert Sanders, the former curator of natural history at the Charleston Museum, who led the excavation of
P. sandersi. There has been little dedicated study of the relationships of
Pelagornis, for while quite a lot of remains are known from the present genus, those of most other pseudotooth birds are few and far between and direct comparisons are further hampered by the damaged state of most remains. The large
Gigantornis eaglesomei from the
Middle Eocene Atlantic was established based on a broken but not too incomplete
sternum and might actually belong in
Dasornis. In
Gigantornis the
articular facet for the
furcula consists of a flat section at the very tip of the
sternal keel and a similar one set immediately above it at an outward angle, and the
spina externa is shaped like an
Old French shield in cross-section. The slightly smaller LHNB (CC-CP)-1 has a less sharply protruding sternal keel, the articular facet for the furcula consists of a large knob at the forward margin, and the spina externa is narrow in cross-section. While these differences are quite conspicuous, the two fossils are clearly of closely related huge
dynamically soaring seabirds, and considering the 30 million years or so that separate
Gigantornis and LHNB (CC-CP)-1, the Paleogene taxon may be very close to the Miocene bird's ancestor nonwithstanding their differences. In any case, the
family name of the pseudotooth birds, Pelagornithidae, as the
senior synonym has widely replaced the once-commonly used Pseudodontornithidae. It may be that
Pseudodontornis belongs to a distinct lineage of these birds, and then the family name would perhaps be revalidated. Also, the presumed similarity between
Dasornis and the smaller
Odontopteryx seems to be a
symplesiomorphy that is not informative regarding their relationships to each other and with
Pelagornis. Rather, it is likely that the huge pseudotooth birds form a
clade, and in this case, Pseudodontornithidae like Cyphornithidae and Dasornithidae is correctly placed in the synonymy of Pelagornithidae even if several families were accepted in the Odontopterygiformes. == Description ==