''Phoeniconaias proeses'' is an extinct species 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 Caribbea ...

from the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Australia. Fossil material was described under several names including ''Ocyplanus proeses'' and ''Phoeniconaias gracilis'', which were eventually found to be synonymous. Only material from the Tirari Formation has been dated, while most other material lacks precise information on its age. ''P. proeses'' was one of the smallest species of flamingo, smaller than the modern

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 lesser ...

which it may be related to.

History

''Phoeniconaias proeses'' was first described by

Charles Walter De Vis Charles Walter de Vis (Birmingham, England, 9 May 1829 – Brisbane, Queensland, Australia, 30 April 1915),

in 1905 alongside a variety of other fossil birds. At the time De Vis was under the impression that the material, a left distal tarsometatarsus only described to have been found in the

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 porti ...

without precise locality or age, belonged to a type of

shorebird 245px, A flock of Dunlins and Red knots">Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflat ...

. Rich and colleagues argue that this identification may have been a result of De Vis' limited reference collection, which did not include bones of flamingos. Subsequently, De Vis was incapable of comparing his material with extant flamingos and instead had to assign it to the most similar group available to him. The material, named ''Ocyplanus proeses'' by De Vis, was then placed in the family

Laridae Laridae is a family of seabirds in the order Charadriiformes that includes the gulls, terns, skimmers and kittiwakes. It includes around 100 species arranged into 22 genera. They are an adaptable group of mostly aerial birds found worldwide. ...

by Lambrecht in 1933, an assignment then supported by

Pierce Brodkorb William Pierce Brodkorb (September 29, 1908, Chicago – July 18, 1992, Gainesville, Florida) was an American ornithologist and paleontologist. Interested in birds since childhood, he was taught to prepare birds at the age of 16. Later, he rec ...

in 1967. Around the same time Miller named the first recognized flamingo fossils from Australia, erecting several species including ''Phoeniconaias gracilis'' from Lake Kanunka in the Lake Eyre basin. In 1975 Condon proposed that ''Ocyplanus proeses'' was not a shorebird at all and instead represented a type of

rail Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

. In 1987, Rich and colleagues examined the material and determined that the description and size of ''O. proeses'' matches Miller's diagnosis for ''Phoeniconaias gracilis'', rendering the later a synonym of De Vis' taxon. In the same publication the authors examine ''Ibis (?) conditus'', also named by De Vis in 1905 based on a femur from Wurdulumankula and placed in

Threskiornithidae The family Threskiornithidae includes 36 species of large wading birds. The family has been traditionally classified into two subfamilies, the ibises and the spoonbills; however recent genetic studies have cast doubt on this arrangement, and ha ...

. The team argues that the femur, stouter than in ibises, more closely resembles flamingos and also assign it to ''Ocyplanus proeses'', which is of similar size. Although the name ''Ocyplanus'' was initially kept due to the differences in the tibiotarsus and femur distinguishing it from the modern

, the combination ''Phoeniconaias proeses'' was used in later publications due to the fact that the name '' Ocyplanus'' is occupied by a beetle.

Description

Based on the surface texture of the fossil, the holotype of ''Phoeniconaias proeses'' is thought to have belonged to a juvenile approximately the size of a

beach stone-curlew The beach stone-curlew (''Esacus magnirostris'') also known as beach thick-knee is a large, ground-dwelling bird that occurs in Australasia, the islands of South-east Asia. At and , it is one of the world's largest shorebirds. At a mean of in ...

. According to Rich ''et al.'', this fossil matches the diagnosis given by Miller for ''Phoeniconaias gracilis''. This diagnosis included that the tarsometatarus was smaller and more slender than the corresponding bone in the lesser flamingo. The posterior extension of the second trochlea is not as rounded and on the plantar surface of the fourth trochlea the articular surface does not extend as far back. The additional material identified by Miller generally matches the corresponding bones in the extant ''Phoeniconaias'' species. Rich and colleagues however do point out that the features of the trochlea are very variable in extant genera, before agreeing that the mediolateral compression of the species most closely resembles the lesser flamingo out of all modern genera. They also add that certain features of the referred material serve as additional differentiation from modern flamingos. This includes the placement of the ligamental groove, the flattened state of the distal end and the sloping of the condyles. The femur originally named ''Ibis (?) conditus'' shows the stout morphology typical for flamingos as well as sharply curved line near the

popliteal fossa The popliteal fossa (also referred to as hough, .html" ;"title="/sup>">/sup> or kneepit in analogy to the cubital fossa) is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia ...

. However, unlike Miller's tarsometatarus which is incredibly similar to ''Phoeniconaias'', this element shows several differences that clearly set it apart from all modern flamingos. For instance, the intermuscular line remains straight over most the femur's length until it makes a drastic concave turn to contact the

trochanter A trochanter is a tubercle of the femur near its joint with the hip bone. In humans and most mammals, the trochanters serve as important muscle attachment sites. Humans are known to have three trochanters, though the anatomic "normal" includes ...

. The front of the shaft is deeply excavated in the proximal region and lacks a foramen that in other flamingos aids with

skeletal pneumaticity Skeletal pneumaticity is the presence of air spaces within bones. It is generally produced during development by excavation of bone by pneumatic diverticula (air sacs) from an air-filled space, such as the lungs or nasal cavity. Pneumatization is h ...

. The pit for the ligament at the fibular condyle is deep, proximal to which lie a prominent ridge and well defined channel. The ridge is only weakly present in modern flamingos and the well defined channel absent. Both Miller and Rich ''et al.'' describe ''Phoeniconaias proeses'' as being among the smallest known flamingo, fossil or otherwise. The type material of ''P. proeses'' is clearly smaller than the same bone in the extant lesser flamingo. The femur described by De Vis is also smaller than in modern ''Phoeniconaias'' and subsequently matches what was described for ''P. proeses''. Miller writes that it's approximately 10% smaller than the smallest individuals of the lesser flamingo and also smaller than the small American forms ''

Phoenicopterus minutus ''Phoenicopterus minutus'' is an extinct species of flamingo which inhabited California during the Late Pleistocene. It was originally discovered in San Bernardino County, California in the Lake Manix beds, where it coexisted with a second, larg ...

'' and ''

Phoenicopterus stocki ''Phoenicopterus stocki'', also known as Stock's flamingo, is an extinct species of flamingo from the Pliocene of Chihuahua, Mexico. It was described in 1944 as a small bodied flamingo species known from assorted fragmentary remains, including b ...

''. Due to this Miller argues that ''P. proeses'', at least based on the Lake Kanunka material, was the smallest known flamingo in the fossil record. Rich and colleagues, who worked with more material of the species, disagree with this, stating that ''

Leakeyornis ''Leakeyornis'' is an extinct genus of flamingo from the early to middle Miocene of Kenya, primarily in the area of modern day Lake Victoria. Initially described as a species of ''Phoenicopterus'' based on an incomplete skull and various limb bon ...

'' from Miocene Kenya was even smaller. Miller did identify a humerus that in size would match the modern lesser flamingo, but also notes that this fossil would not only fall within the range of variation for ''P. proeses'', but might also be deceptive, as the wings may not reflect the small and gracile build of the rest of the body.

Paleobiology

Material assigned to ''Phoeniconaias proeses'' is known from various localities in Australia. During the Pliocene at Lake Kanunka it coexisted with at least two other species of flamingo, the large greater flamingo and '' Xenorhynchopsis minor'', which is approximately the size of the lesser flamingo. It was again found alongside greater flamingos at Wurdulumankula, Lower Wolf Creek, though the precise age of that site is unknown. Although it is unknown when precisely ''Phoeniconaias proeses'' went extinct, flamingos as a whole disappeared from Australia during the Quaternary, when increasing aridification destroyed the shallow lakes these birds require to feed and nest.

References

{{Taxonbar, from=Q115702394 Flamingos Pliocene birds Prehistoric birds of Australia Fossil taxa described in 1905 Phoeniconaias