''Pseudoscaphirhynchus'' 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 relatively small, highly threatened

sturgeon Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early ...

s that are restricted to the

Aral Sea The Aral Sea ( ; kk, Арал теңізі, Aral teñızı; uz, Орол денгизи, Orol dengizi; kaa, Арал теңизи, Aral teńizi; russian: Аральское море, Aral'skoye more) was an endorheic lake lying between Kazak ...

system (although

extirpated Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...

from the Aral Sea itself), including the

Amu Darya The Amu Darya, tk, Amyderýa/ uz, Amudaryo// tg, Амударё, Amudaryo ps, , tr, Ceyhun / Amu Derya grc, Ὦξος, Ôxos (also called the Amu, Amo River and historically known by its Latin name or Greek ) is a major river in Central Asi ...

and

Syr Darya The Syr Darya (, ),, , ; rus, Сырдарья́, Syrdarjja, p=sɨrdɐˈrʲja; fa, سيردريا, Sirdaryâ; tg, Сирдарё, Sirdaryo; tr, Seyhun, Siri Derya; ar, سيحون, Seyḥūn; uz, Sirdaryo, script-Latn/. historically known ...

river basins, in

Central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...

. '' P. fedtschenkoi'' is restricted to Syr Darya, but has not been seen in decades and it is possibly extinct.Mitrofanov, I.V.; and N.Sh. Mamilov (2015). Fish diversity and fisheries in the Caspian Sea and Aral–Syr Darya basin in the Republic of Kazakhstan at the beginning of the 21st Century. Aquatic Ecosystem Health & Management 18(2): 160–170. The two other species in the genus are restricted to Amu Darya: '' P. hermanni'' survives in very low numbers and '' P. kaufmanni'' in low numbers, with both being rated as Critically Endangered by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

.Salnikov, V.B.; V.J. Birstein; and R.L. Mayden (1996). The contemporary status of the two Amu Darya River shovelnose sturgeons, Pseudoscaphirhynchus kaufmanni and P. hermanni. The Sturgeon Quarterly 4(3): 10–14.Kovalev, K.V.; D.A. Balashov; A.L. Cherniak; E. B. Lebedeva; E.D. Vasil'eva; and V.P. Vasil'ev (2016). The karyotype of the Amu Darya sturgeon, Pseudoscaphirhynchus kaufmanni (Actinopterygii: Acipenseriformes: Acipenseridae). Acta Ichthyologica Et Piscatoria 44(2): 111-116. Compared to other sturgeons, ''Pseudoscaphirhynchus'' are small. The largest species, ''P. kaufmanni'', reaches up to in total length (excluding tail filament), while the smallest, ''P. hermanni'', only reaches , making it the smallest member of the sturgeon family. ''P. kaufmanni'' has a long thin tail filament, ''P. hermanni'' lacks it, and it can be long or short in ''P. fedtschenkoi''. They have a relatively long, broad and flattened snout, somewhat like ''

Scaphirhynchus ''Scaphirhynchus'' is a genus of sturgeons native to the United States of America. All species in this genus are considered to be threatened. The pallid sturgeon is Endangered and the Alabama sturgeon is Critically Endangered. Distribution Memb ...

'' of North America. Little is known about the behavior of ''Pseudoscaphirhynchus'', but they mainly feed on the bottom on small fish and aquatic insect larvae.Birstein, V.J.; J.R. Waldman; and W.E. Bemis, editors (1997). Sturgeon biodiversity and conservation, pp. 146, 381–382. Kluwer Academic Publishing.

Taxonomy and species

There are currently three recognized species in this genus: *''

Pseudoscaphirhynchus fedtschenkoi The Syr Darya sturgeon (''Pseudoscaphirhynchus fedtschenkoi'') is a species of fish in the family Acipenseridae. It is found in Kazakhstan, Tajikistan and Uzbekistan, where it is endemic to the Syr Darya River and, before its drainage, the Ar ...

'' (

Kessler Kessler or Keßler (in German) may refer to: * Kessler (automobile), an American automobile made 1921–1922 * Kessler (name), people named Kessler * ''Kessler'' (TV series), a British television series from 1981 * Kessler, Ohio, an unincorporat ...

, 1872) (Syr Darya sturgeon) *''

Pseudoscaphirhynchus hermanni The dwarf sturgeon, little shovelnose sturgeon, or small Amu-Darya shovelnose sturgeon (''Pseudoscaphirhynchus hermanni'') is a species of fish in the family Acipenseridae. It is found in Turkmenistan, Uzbekistan and probably in Tajikistan. P ...

'' (Kessler, 1877) (dwarf sturgeon, small Amu Darya sturgeon) *''

Pseudoscaphirhynchus kaufmanni The Amu Darya sturgeon or false shovelnose sturgeon (''Pseudoscaphirhynchus kaufmanni'') is a critically endangered species of fish in the family Acipenseridae. It is found in Turkmenistan, Uzbekistan, Tajikistan and perhaps Afghanistan. It ...

'' (Kessler, 1877) (Amu Darya sturgeon) Historically, the two species in the Amu Darya River were known to hybridize. Unusually, ''P. fedtschenkoi'' occurs (or occurred) in three morphs that can be separated by the length of their snout and tail filament, and ''P. kaufmanni'' occurs in two morphs that can be separated by their total size and colour. Although ''Pseudoscaphirhynchus'' and ''Scaphirhynchus'' traditionally are placed together in the subfamily

Scaphirhynchinae Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early ...

based on their similar morphology, several genetic and karyotypic studies have shown that this grouping is

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...

References

{{Taxonbar, from=Q311736 Taxonomy articles created by Polbot Ray-finned fish genera Taxa named by Alexander Nikolsky