''Xenorhynchopsis'' is an extinct genus of

flamingo Flamingos or flamingoes () are a type of wading bird in the family Phoenicopteridae, which is the only extant family in the order Phoenicopteriformes. There are four flamingo species distributed throughout the Americas (including the Caribbe ...

from the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

Lake Eyre basin The Lake Eyre basin ( ) is a drainage basin that covers just under one-sixth of all Australia. It is the largest endorheic basin in Australia and amongst the largest in the world, covering about , including much of inland Queensland, large port ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. Initially described as species of stork, the two known ''Xenorhynchopsis'' species are vastly different in size. ''X. minor'' is the older and smaller of the two species, ranging from the Pliocene to Pleistocene and being described as having reached a size smaller than that of the

lesser flamingo The lesser flamingo (''Phoeniconaias minor'') is a species of flamingo occurring in sub-Saharan Africa and western India. Birds are occasionally reported from further north, but these are generally considered vagrants. Characteristics The lesse ...

. ''X. tibialis'' meanwhile appears to have been restricted to Pleistocene strata and was notably bigger, being counted as one of the biggest known flamingos in the fossil record.

History

The fossils of ''Xenorhynchopsis'' were initially described by

Charles Walter de Vis Charles Walter de Vis (9 May 1829 – 30 April 1915)
— Australian Dictionary of Biography was an England, Engli ...

in 1905, who recognized two species he named ''Xenorhynchopsis minor'' and ''Xenorhynchopsis tibialis'' respectively. Possibly due to the fact that de Vis lacked flamingo material in his collection to compare the fossils to, he assigned the genus to the Ciconiidae, the storks. ''X. tibialis'', the larger of the two species, was described on the basis of a

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

and a

tibiotarsus The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia. A similar structure also occurred in the Mesozoic Heterodontosauridae. These ...

found in the Lower Cooper Creek. The smaller species ''X. minor'' meanwhile is known from multiple remains of the humerus and tibiotarsus discovered in Pliocene to Pleistocene sediments of Lake Kanunka and the Lower Cooper Creek. Rich and colleagues, who published a revision of the Pliocene and Pleistocene flamingo fossils of material, write that the remains are too fragmentary to determine whether or not these species should be placed in the same genera as modern flamingos. They subsequently retain the genus names coined by de Vis for the sake of convenience.

Description

The traits that distinguish ''Xenorhynchopsis'' from other flamingo genera are deemed questionable by Rich and colleagues. The distal end of the tibiotarsus is described as deeper than it is wide with a shaft that flares less towards the distal end when compared to extant species. Towards the distal end the tendinal canal has larger openings, another trait shared by both species and setting them apart from modern flamingos. Additionally, the internal condyle lacks a notch in both species. The fossil material of ''X. tibialis'' resembles the black-necked stork in size and is larger than that of extant flamingos. Rich and colleagues write that only ''

Phoeniconotius ''Phoeniconotius'' is an extinct genus of flamingo that lived in Australia from the late Oligocene to the early Miocene. Unlike modern flamingos and the contemporary '' Phoenicopterus novaehollandiae'', it was likely less well adapted for swimmi ...

'' exceeds ''Xenorhynchopsis tibialis'' in size. ''X. minor'' meanwhile is somewhat smaller, if stouter, than the

and approximately in the same size range as '' Phoenicopterus stocki'' and '' Phoenicopterus minutus''.

Paleobiology

During the Pliocene at least three flamingo species existed at Lake Kanunka, ''Xenorhynchopsis minor'', ''Phoeniconaias proeses'' and what may be the modern

greater flamingo The greater flamingo (''Phoenicopterus roseus'') is the most widespread and largest species of the flamingo family. Common in the Old World, they are found in Northern (coastal) and Sub-Saharan Africa, the Indian Subcontinent (south of the Him ...

. ''Xenorhynchopsis tibialis'' appears to have been limited to the Pleistocene and possibly died out when the inland lakes these birds depended on dried up, leading to the local extinction of flamingos in Australia. All four species could be found in the sediments of Lower Cooper Creek, however due to them appearing in different localities, many of which lack precise information regarding their age, it is uncertain if they actually occurred alongside one another. According to Camens and Worthy, footprints found in the Tirari Formation may have been left by ''Xenorhynchopsis minor'', as they appear to be too large to be attributed to ''P. proeses'' and too small to have belonged to ''X. tibialis''. The greater flamingo is however another possible candidate.

References

{{Taxonbar, from=Q115869491 Phoenicopteridae Flamingos Pliocene birds Pleistocene birds Prehistoric birds of Australia Fossil taxa described in 1905 Taxa named by Charles Walter De Vis