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Temporal range: Early Jurassic–Present
Atlantic sturgeon
(Acipenser oxyrhynchus)
American paddlefish
(Polyodon spathula)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Subclass: Chondrostei
Order: Acipenseriformes
L. S. Berg, 1940
Fossil of the chondrosteid Strongylosteus hindenburgi, Tübingen
Fossil of the peipiaosteid Yanosteus longidorsalis, MHNT
The living polyodontid Polyodon spathula (American paddlefish)
The living acipenserid Acipenser ruthenus (sterlet)
The living acipenserid Pseudoscaphirhynchus kaufmanni (false shovelnose sturgeon)

Acipenseriformes /æsɪˈpɛnsərɪfɔːrmz/ is an order of basal[1] ray-finned fishes that includes living and fossil sturgeons and paddlefishes (Acipenseroidei), as well as the extinct families Chondrosteidae and Peipiaosteidae.[2][3][4] They are the second earliest diverging group of living ray-finned fish after the bichirs. Despite being early diverging, they are highly derived, having only weakly ossified skeletons that are mostly made of cartilage, and in modern representatives highly modified skulls.[5]


The axial skeleton of Acipenseriformes is only partially ossified, with the majority of the bones being replaced with cartilage. The notochord, usually only found in fish embryos, is unconstricted and retained throughout life.[6] The premaxilla and maxilla bones of the skull present in other vertebrates have been lost. While larvae and early juvenile acipenseriforms have teeth, the adults are toothless, or nearly so. The infraorbital nerve is carried by a series of separate canals, rather than being within the circumorbital bones. The palatoquadrate bones of the skull possess a cartilaginous symphysis (joint), and also have a broad autopalatine plate, as well as a narrow palatoquadrate bridge, and a quadrate flange. The quadratojugal bone is three-pointed (triradiate), and the dentition on the gill-arch is confined to the upper part of the first arch and to only the first and second hypobranchials.[5] Members of Acipenseriformes retain the ability to sense electric fields (electroreception) using structures called ampullae. This ability was present in the last common ancestor of all living jawed fish, but was lost in the ancestor of neopterygian fish.[7] All acipenseriforms probably possessed barbels like modern sturgeon (which have four) and paddlefish (which have two).[5]

Evolutionary history[edit]

Acipenseriforms are assumed to have evolved from a "palaeoniscoid" ancestor. Their closest relatives within the "palaeoniscoids" are uncertain and contested.[5] The ancestors of Acipenseriformes are thought to have split from those of other living fish around the Carboniferous period (360-300 million years ago).[8] The last common ancestor of Acipenseriformes underwent a whole genome duplication event suggested to have occurred around 242–255 million years ago, with the genome subsequently undergoing rediploidization, both before the split between sturgeons and paddlefish, and separately in both lineages after the split.[9]

Eochondrosteus from the Early Triassic (252-247 million years ago) of China has been suggested by some authors to be the oldest acipenseriform.[10] The oldest unambiguous members of the order are the Chondrosteidae, a group of large fish found in marine deposits from the Early Jurassic (201-175 million years ago) of Europe, which already have reduced ossification of the skeleton.[11] The Peipiaosteidae are known from Middle Jurassic-Early Cretaceous freshwater deposits in Asia.[12] The estimated time of the divergence between sturgeons and paddlefish varies. An estimate based on 30 protein-encoding nuclear markers suggest 204.1 million years ago, research on mitochondrial genomes suggest 155.2 million years ago, and Bayesian dating based on the combined matrix of molecular (mitogenomes) and morphological characters set the divergence to 162 (195–137) million years ago.[13]

The oldest known paddlefish is Protopsephurus from the Early Cretaceous of China around 120 million years ago,[14] while the earliest known sturgeons appear in the Late Cretaceous in North America and Asia, around 100-95 million years ago.[15]



Most living species of Acipenseriformes are classified as threatened (mostly endangered or critically endangered) by the International Union for Conservation of Nature.

The Chinese paddlefish was last seen alive in 2003, and was considered to have gone extinct sometime between 2005 and 2010 by the Yangtze River Fisheries Research Institute in their 2019 report.


A study published in 2020 reported a successful hybridization between a Russian sturgeon (Acipenser gueldenstaedtii) and an American paddlefish (Polyodon spathula), indicating that the two species can breed with one another despite their lineages having been separated for hundreds of millions of years. This has marked the first successful hybridization between members of Acipenseridae and Polyodontidae.[18]


  1. ^ Venkatesh, B. (December 2003). "Evolution and diversity of fish genomes". Current Opinion in Genetics & Development. 13 (6): 588–592. doi:10.1016/j.gde.2003.09.001. PMID 14638319.
  2. ^ Froese, Rainer, and Daniel Pauly, eds. (2006). "Acipenseriformes" in FishBase. 05 2006 version.
  3. ^ Bemis, William E.; Findeis, Eric K.; Grande, Lance (1997). "An overview of Acipenseriformes". Environmental Biology of Fishes. 48 (1–4): 25–71. doi:10.1023/A:1007370213924. S2CID 24961905.
  4. ^ Lu, Liwu; Tan, Kai; Wang, Xi (2020). "Redescription of Eochondrosteus sinensis (Acipenseriformes, Actinopterygii) and its geological age". Earth Science Frontiers. 27 (6): 371–381.
  5. ^ a b c d Bemis, William E.; Findeis, Eric K.; Grande, Lance (2002), Birstein, Vadim J.; Waldman, John R.; Bemis, William E. (eds.), "An overview of Acipenseriformes", Sturgeon Biodiversity and Conservation, vol. 17, Dordrecht: Kluwer Academic Publishers, pp. 25–71, doi:10.1007/0-306-46854-9_4, ISBN 978-0-7923-4517-6, retrieved 2022-07-27
  6. ^ Leprévost, A.; Sire, J.-Y. (August 2014). "Architecture, mineralization and development of the axial skeleton in Acipenseriformes, and occurrences of axial anomalies in rearing conditions; can current knowledge in teleost fish help?". Journal of Applied Ichthyology. 30 (4): 767–776. doi:10.1111/jai.12525.
  7. ^ Crampton, William G. R. (July 2019). "Electroreception, electrogenesis and electric signal evolution". Journal of Fish Biology. 95 (1): 92–134. doi:10.1111/jfb.13922. ISSN 0022-1112. PMID 30729523. S2CID 73442571.
  8. ^ Friedman, Matt (2022-11-02). "The Macroevolutionary History of Bony Fishes: A Paleontological View". Annual Review of Ecology, Evolution, and Systematics. 53 (1): 353–377. doi:10.1146/annurev-ecolsys-111720-010447. ISSN 1543-592X.
  9. ^ Redmond, Anthony K.; Casey, Dearbhaile; Gundappa, Manu Kumar; Macqueen, Daniel J.; McLysaght, Aoife (2023-05-19). "Independent rediploidization masks shared whole genome duplication in the sturgeon-paddlefish ancestor". Nature Communications. 14 (1): 2879. doi:10.1038/s41467-023-38714-z. ISSN 2041-1723.
  10. ^ Lu, Liwu; Tan, Kai; Wang, Xi (2020). "Redescription of Eochondrosteus sinensis (Acipenseriformes, Actinopterygii) and its geological age". Earth Science Frontiers (in Chinese). 27 (6): 371–381.
  11. ^ Hilton, Eric J.; Forey, Peter L. (December 2009). "Redescription of † Chondrosteus acipenseroides Egerton, 1858 (Acipenseriformes, †Chondrosteidae) from the lower Lias of Lyme Regis (Dorset, England), with comments on the early evolution of sturgeons and paddlefishes". Journal of Systematic Palaeontology. 7 (4): 427–453. doi:10.1017/S1477201909002740. ISSN 1477-2019. S2CID 86821521.
  12. ^ Hilton, Eric J.; Grande, Lance; Jin, Fan (2020-10-08). "Redescription of †Yanosteus longidorsalis Jin et al., (Chondrostei, Acipenseriformes, †Peipiaosteidae) from the Early Cretaceous of China". Journal of Paleontology. 95 (1): 170–183. doi:10.1017/jpa.2020.80. ISSN 0022-3360. S2CID 225158727.
  13. ^ Ruban, G. I. (2023-04-01). "Modern Concepts on the Origin and Distribution of Acipenserids (Acipenseridae)". Journal of Ichthyology. 63 (2): 206–215. doi:10.1134/S0032945223020169. ISSN 1555-6425.
  14. ^ Grande, Lance; Jin, Fan; Yabumoto, Yoshitaka; Bemis, William E. (2002-07-08). "Protopsephurus liui, a well-preserved primitive paddlefish (Acipenseriformes: Polyodontidae) from the Lower Cretaceous of China". Journal of Vertebrate Paleontology. 22 (2): 209–237. doi:10.1671/0272-4634(2002)022[0209:PLAWPP]2.0.CO;2. ISSN 0272-4634. S2CID 86258128.
  15. ^ Sato, Hiroki; Murray, Alison M.; Vernygora, Oksana; Currie, Philip J. (2018-07-04). "A rare, articulated sturgeon (Chondrostei: Acipenseriformes) from the Upper Cretaceous of Dinosaur Provincial Park, Alberta, Canada". Journal of Vertebrate Paleontology. 38 (4): (1)–(15). doi:10.1080/02724634.2018.1488137. ISSN 0272-4634. S2CID 92574712.
  16. ^ Nelson, Joseph S.; Grande, Terry C.; Wilson, Mark V. H. (2016-02-22). Fishes of the World. Wiley. ISBN 978-1-118-34233-6.
  17. ^ Grande, L. & Bemis, W.E. (1996). "Interrelationships of Acipenseriformes, with Comments on 'Chondrostei'". In Stiassny, M.L.J.; Parenti, L.R. & Johnson, G.D. (eds.). Interrelationships of Fishes. San Diego, California: Academic Press. pp. 85–115. doi:10.1016/B978-012670950-6/50006-0. ISBN 0-12-670950-5. LCCN 96028224. OCLC 34990143. OL 989905M.
  18. ^ Káldy, Jenő; Mozsár, Attila; Fazekas, Gyöngyvér; Farkas, Móni; Fazekas, Dorottya Lilla; Fazekas, Georgina Lea; Goda, Katalin; Gyöngy, Zsuzsanna; Kovács, Balázs; Semmens, Kenneth; Bercsényi, Miklós (July 2020). "Hybridization of Russian Sturgeon (Acipenser gueldenstaedtii, Brandt and Ratzeberg, 1833) and American Paddlefish (Polyodon spathula, Walbaum 1792) and Evaluation of Their Progeny". Genes. 11 (7): 753. doi:10.3390/genes11070753. PMC 7397225. PMID 32640744.

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