Gigantornis
Encyclopedia
Gigantornis eaglesomei was a giant prehistoric bird, described from a fragmentary specimen from the Eocene
of Nigeria
. It was considered to be a representative of the albatross
family (Diomedeidae), but was later referred to the bony-toothed birds, (Pelagornithidae). One of the largest pseudotooth birds, with an inferred
wingspan of about 6 m (20 ft) it is among the largest birds ever.
Its identified remains consist of a broken sternum
found in Middle Eocene Ameki Formation
deposits at Ameki (Nigeria
). The fossil
bird was considered to belong the albatross
family
(Diomedeidae), as no sterna of pseudotooth birds were known until its discovery, and it remained the only such specimen for decades. Only in the 1970s its true affinities were realized, after it had become clear that although it must have been from a dynamic soarer with wings like an albatross, it resembled pelicans (order
Ciconiiformes) rather than tubenose
s (order Procellariiformes, to which albatrosses belong) in its details.
It is not known whether this bird belongs to a distinct genus; it might even be the very same species as the similar-sized Dasornis emuinus, whose fossils are not uncommon in the Ypresian
(Early Eocene) London Clay
of the Isle of Sheppey
(England
). Remains of a large pseudotooth bird were also found in the Middle Eocene of Kpogamé-Hahotoé (Togo
) and have been provisionally termed "Aequornis traversei"; their analysis is likely to provide at least some insight on the taxonomic status of G. eaglesomei.
The Gigantornis sternum is of the typical short and deep-crested shape found in dynamic soarers. Compared to LHNB (CCCP)-1, a Middle
to Late Miocene
pseudotooth bird sternum found in Portugal
and tentatively assigned to Pelagornis
, its 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 (CCCP)-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.
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
. It was considered to be a representative of the albatross
Albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
family (Diomedeidae), but was later referred to the bony-toothed birds, (Pelagornithidae). One of the largest pseudotooth birds, with an inferred
Inference
Inference is the act or process of deriving logical conclusions from premises known or assumed to be true. The conclusion drawn is also called an idiomatic. The laws of valid inference are studied in the field of logic.Human inference Inference is the act or process of deriving logical conclusions...
wingspan of about 6 m (20 ft) it is among the largest birds ever.
Its identified remains consist of a broken sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
found in Middle Eocene Ameki Formation
Ameki Formation
The Ameki Formation is a palaeontological formation located in Nigeria. It dates to the Middle Eocene....
deposits at Ameki (Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
). The fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
bird was considered to belong the albatross
Albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
(Diomedeidae), as no sterna of pseudotooth birds were known until its discovery, and it remained the only such specimen for decades. Only in the 1970s its true affinities were realized, after it had become clear that although it must have been from a dynamic soarer with wings like an albatross, it resembled pelicans (order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Ciconiiformes) rather than tubenose
Tubenose
Tubenose may refer to:* Birds in the order Procellariiformes.* Fishes in the family Aulorhynchidae....
s (order Procellariiformes, to which albatrosses belong) in its details.
It is not known whether this bird belongs to a distinct genus; it might even be the very same species as the similar-sized Dasornis emuinus, whose fossils are not uncommon in the Ypresian
Ypresian
In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between and , is preceded by the Thanetian age and is followed by the Eocene Lutetian age....
(Early Eocene) London Clay
London Clay
The London Clay Formation is a marine geological formation of Ypresian age which crops out in the southeast of England. The London Clay is well known for the fossils it contains. The fossils from the Lower Eocene indicate a moderately warm climate, the flora being tropical or subtropical...
of the Isle of Sheppey
Isle of Sheppey
The Isle of Sheppey is an island off the northern coast of Kent, England in the Thames Estuary, some to the east of London. It has an area of . The island forms part of the local government district of Swale...
(England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
). Remains of a large pseudotooth bird were also found in the Middle Eocene of Kpogamé-Hahotoé (Togo
Togo
Togo, officially the Togolese Republic , is a country in West Africa bordered by Ghana to the west, Benin to the east and Burkina Faso to the north. It extends south to the Gulf of Guinea, on which the capital Lomé is located. Togo covers an area of approximately with a population of approximately...
) and have been provisionally termed "Aequornis traversei"; their analysis is likely to provide at least some insight on the taxonomic status of G. eaglesomei.
The Gigantornis sternum is of the typical short and deep-crested shape found in dynamic soarers. Compared to LHNB (CCCP)-1, a Middle
Middle Miocene
The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene....
to Late Miocene
Late Miocene
The Late Miocene is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch....
pseudotooth bird sternum found in Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
and tentatively assigned to Pelagornis
Pelagornis
Pelagornis is a widely-known genus of the 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....
, its articular facet
Articular facet
An articular facet is a surface where two anatomical structures meet.-Structures with articular facets:* cricoid cartilage* lateral malleolus* medial malleolus* tubercle of rib...
for the furcula
Furcula
The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....
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 (CCCP)-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.