''Lithornis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of extinct paleognathous birds. Although ''Lithornis'' was able to fly well, their closest relatives are the extant

tinamou Tinamous () form an order of birds called Tinamiformes (), comprising a single family called Tinamidae (), divided into two distinct subfamilies, containing 46 species found in Mexico, Central America, and South America. The word "tinamou" come ...

s (which are poor flyers) and ratites (which are

flightless bird Flightless birds are birds that through evolution lost the ability to fly. There are over 60 extant species, including the well known ratites (ostriches, emu, cassowaries, rheas, and kiwi) and penguins. The smallest flightless bird is the ...

s). Fossils of ''Lithornis'' are known with certainty from the Upper

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

through the

Middle Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "da ...

, but their fossil record may extend to the late Cretaceous. "''Lithornis''" is from ancient Greek for "stone bird", as it is one of the first fossil birds to become widely discussed. Presumably closely related genera are ''

Paracathartes ''Paracathartes'' is a genus of extinct bird from the Wasachtian horizon of lower Eocene Wyoming. One species, ''Paracathartes howardae'' has been described. It is a paleognathous bird, turkey-like in stature and size, that probably resembled ...

'' and '' Pseudocrypturus''.

Species

Six

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

have been recognized in modern times; undescribed ones are also likely to exist. The supposed tarsometatarsus piece from which ''"Lithornis" emuinus'' was described is actually a humerus fragment of the giant

pseudotooth bird The Pelagornithidae, commonly called pelagornithids, pseudodontorns, bony-toothed birds, false-toothed birds or pseudotooth birds, are a prehistoric family of large seabirds. Their fossil remains have been found all over the world in rocks dating ...

Dasornis ''Dasornis'' is a 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. ...

''.Houde, P. (1988)

''Lithornis celetius''

''L. celetius'' is from the Bangtail Quarry, Sedan Quadrangle, Park County, Montana, USA, and was described by Peter Houde (1988). It is from the

Fort Union Formation The Fort Union Formation is a geologic unit containing sandstones, shales, and coal beds in Wyoming, Montana, and parts of adjacent states. In the Powder River Basin, it contains important economic deposits of coal, uranium, and coalbed methane. ...

, which is earliest

Tiffanian The Tiffanian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 60,200,000 to 56,800,000 years BP lasting . It is usually c ...

, Late

. The type fossil is USNM 290601. ''L. celetius'' was of average size for the genus, and the name ''Celetius'' is derived from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word ''keletion'' a race horse for which the type locality is also named.

''Lithornis hookeri''

Harrison and Walker originally labeled the fossil as belonging to the species '' Pediorallus barbarae'' in 1977. In 1984, Harrison redescribed the fossil as coming from a new species ''Pediorallus hookeri'', and later that year it was moved to ''Lithornis hookeri''.Mayr, G. (2008) ''L. hookeri'' is the smallest of the Lithornithidae.

''Lithornis nasi''

W. George collected the original

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

in the Division A

London Clay The London Clay Formation is a marine geological formation of Ypresian (early Eocene Epoch, c. 56–49 million years ago) age which crops out in the southeast of England. The London Clay is well known for its fossil content. The fossils from t ...

, North Sea Basin at Walton on the Naze,

Essex Essex () is a county in the East of England. One of the home counties, it borders Suffolk and Cambridgeshire to the north, the North Sea to the east, Hertfordshire to the west, Kent across the estuary of the River Thames to the south, and Grea ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. The fossil was described by Harrison in 1984 as a rail, ''Pediorallus nasi'', but was later moved to ''Lithornis nasi''. ''L. nasi'' is larger than ''L. hookeri'' and ''L. plebius''.

''Lithornis plebius''

''L. plebius'' is from the same locality as ''L. promiscuus'' and was also described by Peter Houde (1988). The type specimen is USNM 336534.

''Lithornis promiscuus''

''L. promiscuus'' has

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...

USNM 336535 and was described by Peter Houde (1988). It is from the Clark Quadrangle, Park County, Wyoming, USA. It is from the Willwood Formation, which is earliest

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

in age. An egg, USNM 336570, is known for ''L. celetius'' as well.

''Lithornis vulturinus''

''L. vulturinus'' was described as a vulture by Owen (1840) from the holotype fossil 955 738 - TM 024 717. The fossil was collected from Early Eocene

deposits on the Isle of Sheppey, Kent, England by J. Hunter before 1793. This fossil was destroyed by bombing in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. Numerous isolated fossil bones of ''Lithornis vulturinus'' were incorrectly described anew, such as ''Parvigyps praecox'' and ''Promusophaga magnifica'' - the supposed earliest vulture and turaco, while others were referred to existing families of neognathous birds. A

neotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

(BMNH A 5204) was erected to replace the holotype in 1988 by Houde, who for the first time diagnosed it as a paleognath based on complete three-dimensional skulls and skeletons of congeners from North America. An exceptionally preserved specimen was collected from Denmark and cataloged as MGUH 26770.Leonard, L. & Van Tuinen, M. (2005)

Palaeobiology

''Lithornis wing bones are similar to those of storks and vultures, meaning that unlike modern tinamous it was capable of soaring flight.Houde, Peter W. (1988). "Paleognathous Birds from the Early Tertiary of the Northern Hemisphere". Publications of the Nuttall Ornithological Club (Cambridge, MA)Paleogene Fossil Birds
/ref> In a study about ratite endocasts, ''Lithornis'' ranks among the taxa with well developed olfactory lobes. This is consistent with a nocturnal, forest-dwelling lifestyle, though as much all volant birds it retains large optical lobes. Unlike modern tinamous, ''Lithornis'' has toe claws and reversed halluxes that allow for efficient perching. Several egg fossils have been attributed to ''Lithornis''. Their eggshells are, perhaps unsurprisingly, noted as being "ratite-like".Gerald Grellet-Tinner and Gareth J. Dyke, The eggshell of the Eocene bird Lithornis, Acta Palaeontologica Polonica 50 (4), 2005: 831-835

References

Footnotes Sources * * * * {{Taxonbar, from=Q6648154 Paleognathae Paleocene birds Eocene birds of Europe Paleogene birds of Europe Bartonian extinctions Paleogene birds of North America