''Pseudoscaphirhynchus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of relatively small, highly threatened

sturgeon Sturgeon (from Old English ultimately from Proto-Indo-European language, Proto-Indo-European *''str̥(Hx)yón''-) is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the ...

s that are restricted to the

Aral Sea The Aral Sea () was an endorheic lake lying between Kazakhstan to its north and Uzbekistan to its south, which began shrinking in the 1960s and had largely dried up into desert by the 2010s. It was in the Aktobe and Kyzylorda regions of Kazakhst ...

system (although

extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...

from the Aral Sea itself), including the

Amu Darya The Amu Darya ( ),() also shortened to Amu and historically known as the Oxus ( ), is a major river in Central Asia, which flows through Tajikistan, Turkmenistan, Uzbekistan, and Afghanistan. Rising in the Pamir Mountains, north of the Hindu Ku ...

and

Syr Darya The Syr Darya ( ),; ; ; ; ; /. historically known as the Jaxartes ( , ), is a river in Central Asia. The name, which is Persian language, Persian, literally means ''Syr Sea'' or ''Syr River''. It originates in the Tian Shan, Tian Shan Mountain ...

river basins, in

Central Asia Central Asia is a region of Asia consisting of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian language, Pers ...

. '' 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 An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

.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 North America. All species in this genus are considered to be Threatened species, threatened with extinction or worse. As of 2023, the pallid sturgeon (''S. albus'') and the Alabama sturgeon ( ...

'' 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''), or Syr Darya shovelnose sturgeon, is a species of fish in the family Acipenseridae. It is found in Kazakhstan, Tajikistan and Uzbekistan, where it is Endemism, endemic to the Syr Da ...

'' ( Kessler, 1872) (Syr Darya sturgeon) *''

Pseudoscaphirhynchus hermanni ''Pseudoscaphirhynchus'' is a genus of relatively small, highly threatened sturgeons that are restricted to the Aral Sea system (although extirpated from the Aral Sea itself), including the Amu Darya and Syr Darya river basins, in Central Asia. ...

'' (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 (biology), family Acipenseridae. It is found in Turkmenistan, Uzbekistan, Tajikistan and perhaps Af ...

'' (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 (from Old English ultimately from Proto-Indo-European *''str̥(Hx)yón''-) 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 desce ...

based on their similar

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

, several genetic and

karyotypic A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by de ...

studies have shown that this grouping is

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

References

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