Sturgeon are 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 Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America. Sturgeons are long-lived, late-maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle-like body that is smooth-skinned, scaleless, and armored with five lateral rows of bony plates called scutes.
Several species can grow quite large, typically ranging in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring long and weighing . The family is grouped into five genera: Acipenser, Huso, Scaphirhynchus, Sinosturio, and Pseudoscaphirhynchus. One species (S. dabryanus) may be extinct in the wild, and another (P. fedtschenkoi) may be entirely extinct. Beginning in 2011 H. naccarii was presumed extinct in the wild, but in 2022 was downgraded to critically endangered. A Maastrichtian-age fossil found in Morocco shows that they also once lived in northern Africa during the Cretaceous.
Most sturgeons are anadromous bottom-feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean. The roe some of these sturgeon species spawn are harvested and processed into luxurious caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction.
Etymology The English word Sturgeon comes from Middle English itself from Old French , displacing Old English though both are derived from Proto-Germanic .
Apparent cognates to Sturgeon might be found in Baltic, Germanic, Greek, Romance, and Slavic languages. The trade of sturgeon in ancient Europe would cause for the root word for these to spread across the region. Many potential reconstructions may place it as either a non-Indo-European substrate language, possibly from around the Volga river, where sturgeon could be caught and sold, while others reconstruct a Proto-Indo-European source.
One reconstruction links Sturgeon to ultimately derive from Proto-Indo-European *str̥(Hx)yón-.
Evolution
Fossil history
Acipenseriform fishes appeared in the fossil record some 174 to 201 million years ago, during the Early Jurassic, making them some of the earliest extant actinopterygian fishes. Sturgeons must have diverged from their closest relatives, the paddlefish, during the Early Cretaceous (125-120 million years ago) or prior, as the earliest fossil paddlefish (Protopsephurus) is known from then. True sturgeons appear in the fossil record during the Upper Cretaceous, with amongst the oldest known remains being a partial skull from the Cenomanian (100–94 million years ago) of Alberta, Canada. In that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils.B. G. Gardiner (1984) Sturgeons as living fossils. Pp. 148–152 in N. Eldredge and S.M. Stanley, eds. Living fossils. Springer-Verlag, New York. This is explained in part by the long generation interval, tolerance for wide ranges of temperature and salinity, lack of predators due to size and bony plated armor, or scutes, and the abundance of prey items in the benthic environment. They do, however, still share several primitive characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements, and unique jaw suspension.
Phylogeny and taxonomy
Despite the existence of a fossil record, full classification and phylogeny of the sturgeon species has been difficult to determine, in part due to the high individual and ontogenic variation, including geographical clines in certain features, such as rostrum shape, number of scutes, and body length. A further confounding factor is the peculiar ability of sturgeons to produce reproductively viable hybrids, even between species assigned to different genera. While ray-finned fishes (Actinopterygii) have a long evolutionary history culminating in the most familiar fishes, past adaptive evolutionary radiations have left only a few survivors, such as sturgeons and gars.
The phylogeny of Acipenseridae, as in the cladogram, shows that they evolved from the bony fishes. In currently accepted taxonomy, the class Actinopterygii and the order Acipenseriformes are both clades. Approximate dates are from Near et al., 2012.
The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult. The factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. An effort is ongoing to resolve the taxonomic confusion using a continuing synthesis of systematic data and molecular techniques.
Sturgeons are a highly morphologically conservative group, to the extent that lineages that (based on molecular data) have been separate since the Cretaceous period can physically appear very similar, and mistakenly classified as each other's closest relatives. In the classic taxonomic treatment, Acipenseridae was subdivided into 2 subfamilies; Acipenserinae, including the genera Acipenser and Huso, and Scaphirhynchinae, including the genera Scaphirhynchus and Pseudoscaphirhynchus. The family name comes from the genus Acipenser, which its name is Latin for "sturgeon"; that name is derived from akkipesios in Greek from the words akís meaning "point", and pénte meaning "five" referring to the five rows of sharp scutes found on its body.
Under a phylogeny that exclusively incorporates morphological data, sturgeons appear to comprise two groups that diverged during the Cretaceous: a Scaphirhynchus lineage, and a Acipenser+Huso+Pseudoscaphirhynchus lineage. The latter seemingly appears rather young compared to the age of the group as a whole, with much of its radiation only occurring during the Late Paleogene and Neogene. However, with the advent of molecular phylogenetics, multiple studies since the 1990s have recovered this arrangement as paraphyletic, instead finding A. oxyrhinchus and A. sturio to form the most basal clade among sturgeons, and all other species being in a separate clade, with the various other species of Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, and Huso to have varying levels of relationship with one another. The morphologically distinct "shovelnose" type sturgeons are deeply nested within the former "Acipenser" and "Huso" clades. The divergences within the group have also been found to be much deeper, with Acipenser sensu stricto diverging from the rest of the group well into the Cretaceous. The other lineages were found to have diverged from one another during the Late Cretaceous and Paleogene.
The exact placement of Scaphirhynchus varies depending on the study and the methods used, with some placing it within the second-most basal clade comprising primarily Pacific species, whereas others place it in its own clade that is more derived than the secondmost basal clade but less derived than the most derived Atlantic and Central Asian clade. No studies have yet delineated a relationship between it and Pseudoscaphirhynchus. In addition, the exact relationships of the members of the most derived, primarily Atlantic clade vary, although most analyses at least find all the species in it to form a monophyletic clade. The placement of A. sinensis also varies by the study, with some placing it as the only Pacific member of the otherwise Atlantic-based most-derived clade, whereas others place it with the rest of the Pacific sturgeons as a sister to A. dabryanus.
Brownstein & Near (2025) used DNA sequencing and morphological data to establish 5 monophyletic genera for Acipenseridae and mostly resolve the longstanding confusion over clade names. The 5 clades found were Acipenser sensu stricto, Scaphirhynchus, Pseudoscaphirhynchus, Huso, and the revived genus Sinosturio, as well as moving species out of Acipenser and into the latter two genera (including the kaluga, now Sinosturio dauricus).
The following taxonomy is based on Brownstein & Near, 2025:
Species The family contains 27 recent species in 5 genera, as well as a number of fossil species and genera.
The following classification is based on Eschmeyer's Catalog of Fishes (2025):
Family Acipenseridae Genus Acipenser Linnaeus, 1758 (native to eastern North America and western Europe) Acipenser desotoi Vladykov, 1955 (Gulf sturgeon) Acipenser oxyrinchus Mitchill, 1815 (Atlantic sturgeon) Acipenser sturio Linnaeus, 1758 (European sea sturgeon) Genus Scaphirhynchus Heckel, 1835 (native to central North America) Scaphirhynchus albus (Forbes & R. E. Richardson, 1905) (pallid sturgeon) Scaphirhynchus platorynchus (Rafinesque, 1820) (shovelnose sturgeon) Scaphirhynchus suttkusi J. D. Williams & Clemmer, 1991 (Alabama sturgeon) Genus Sinosturio Jaekel in Weigelt, 1929 (native to East Asia and western North America) Sinosturio dabryanus (A. H. A. Duméril, 1869) (Yangtze sturgeon) Sinosturio dauricus (Georgi, 1775) (kaluga) Sinosturio medirostris (Ayres, 1854) (green sturgeon) Sinosturio mikadoi (Hilgendorf, 1892) (Sakhalin sturgeon) Sinosturio schrenckii (J. F. Brandt, 1869) (Amur sturgeon) Sinosturio sinensis (J. E. Gray, 1835) (Chinese sturgeon) Sinosturio transmontanus (J. Richardson, 1836) (white sturgeon) Genus Huso J. F. Brandt & Ratzeburg, 1833 (native to eastern Europe, west Asia, and eastern North America) Huso baerii (J. F. Brandt, 1869) (Siberian sturgeon) Huso baerii baicalensis (A. M. Nikolskii, 1896) (Baikal sturgeon) Huso baerii stenorrhynchus (A. M. Nikolskii, 1896) Huso brevirostrum (Lesueur, 1818) (shortnose sturgeon) Huso colchicus (Marty, 1940) (Caucasian sturgeon) Huso fulvescens (Rafinesque, 1817) (lake sturgeon) Huso gueldenstaedtii (J. F. Brandt & Ratzeburg, 1833) (Russian sturgeon) Huso huso (Linnaeus, 1758) (beluga) Huso naccarii (Bonaparte, 1836) (Adriatic sturgeon) Huso nudiventris (Lovetsky, 1828) (fringebarbel sturgeon) Huso persicus (Borodin, 1897) (Persian sturgeon) Huso ruthenus (Linnaeus, 1758) (sterlet) Huso stellatus (Pallas, 1771) (starry sturgeon) Genus Pseudoscaphirhynchus Nikolskii, 1900 (native to Central Asia) Pseudoscaphirhynchus fedtschenkoi (Kessler, 1872) (Syr Darya sturgeon) Pseudoscaphirhynchus hermanni (Kessler, 1877) (dwarf sturgeon) Pseudoscaphirhynchus kaufmanni (Kessler, 1877) (Amu Darya sturgeon)
Fossil taxa
Fossil sturgeons are known from the mid-late Cretaceous onwards. The earliest known sturgeon fossil is of an indeterminate partial skull from the Cenomanian-aged Dunvegan Formation of Alberta, Canada. It was previously assumed that from Asiacipenser kotelnikovi Nessov, 1990 from the Late Jurassic of Kazakhstan was the earliest sturgeon, but these remains are non-diagnostic and it is unlikely that it represents a member of the family. They become particularly diverse during the Late Cretaceous of North America, where multiple different genera are known.
The following species are known: Genus "Acipenser" Linnaeus, 1758 (Acipenser sensu lato) †"Acipenser" albertensis Lambe, 1902 (Late Cretaceous of Alberta, Canada) †"Acipenser" anisinferos Hilton & Grande, 2023 (Late Cretaceous of North Dakota, USA) †"Acipenser" chilini Nessov, 1983 (Early Paleocene of Kazakhstan)