# Cyclurus

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Extinct genus of ray-finned fishes

Cyclurus Temporal range: Maastrichtian to Rupelian PreꞒ Ꞓ O S D C P T J K Pg N Possible Campanian occurrence Fossil of C. kehreri Scientific classification Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Clade: Halecomorphi Order: Amiiformes Family: Amiidae Subfamily: Amiinae Genus: †Cyclurus Agassiz, 1844 Type species †Cyclurus valenciennesi Agassiz, 1844 Species See text Synonyms †Kindleia Jordan, 1927 †Paramiatus Romer & Fryxell, 1928 †Stylomyleodon Russell, 1928

Not to be confused with [Cyclura](/source/Cyclura).

***Cyclurus*** (Ancient Greek for "rounded tail") is an extinct [genus](/source/Genus) of freshwater [amiid](/source/Amiidae) [ray-finned fish](/source/Actinopterygii) known from the [Late Cretaceous](/source/Late_Cretaceous) to the [Early Oligocene](/source/Rupelian) across much of the [Northern Hemisphere](/source/Northern_Hemisphere).[1] It is thought to be the closest relative of the extant [bowfins](/source/Bowfin) in the genus *[Amia](/source/Amia_(fish))*, although species of *Cyclurus* were significantly smaller in size compared to *Amia*.[2]

## Evolution

Remains of *Cyclurus* are first known from western North America during the [Maastrichtian](/source/Maastrichtian) stage of the [Cretaceous](/source/Cretaceous) with the species *C. fragosus*, with the genus having presumably diverged from *[Amia](/source/Amia_(fish))* shortly before. Potential earlier remains are known from the [Campanian](/source/Campanian).[1][2] Alongside *Amia*, *Cyclurus* survived the [Cretaceous-Paleogene extinction event](/source/Cretaceous%E2%80%93Paleogene_extinction_event) in a [refugium](/source/Refugium_(population_biology)) in western North America.[2] Shortly afterwards, it saw a dramatic range expansion over the [Paleogene](/source/Paleogene), colonizing Europe and Asia by the [Late Paleocene](/source/Thanetian) and becoming particularly successful and speciose in Europe. By the Late Eocene, it was one of the last two surviving [halecomorph](/source/Halecomorphi) genera, alongside *Amia*. However, alongside most *Amia* species aside from those in eastern North America, it became extinct during the [Oligocene](/source/Oligocene).[2][3]

## Taxonomy

The following species are known:[3]

- †***C. efremovi*** (Sytchevskaya, 1981) - late Paleocene of [Mongolia](/source/Mongolia) ([Naran Bulak Formation](https://en.wikipedia.org/w/index.php?title=Naran_Bulak_Formation&action=edit&redlink=1)) (=*Amia efremovi* Sytchevskaya, 1981). Named for [Ivan Yefremov](/source/Ivan_Yefremov).

- †***C. fragosus*** ([Jordan](/source/David_Starr_Jordan), 1927) - [Late Cretaceous](/source/Late_Cretaceous) ([Maastrichtian](/source/Maastrichtian)) of [Alberta](/source/Alberta), Canada ([Scollard Formation](/source/Scollard_Formation)) and [Montana](/source/Montana), [North Dakota](/source/North_Dakota), [South Dakota](/source/South_Dakota) and [Wyoming](/source/Wyoming), USA ([Hell Creek Formation](/source/Hell_Creek_Formation), [Fox Hills Formation](/source/Fox_Hills_Formation)) (=*Kindleia fragosa* Jordan, 1927)[4][5][6]

- †***C. gurleyi*** ([Romer](/source/Alfred_Romer) & [Fryxell](/source/Fritiof_Fryxell), 1928) - early Eocene ([Ypresian](/source/Ypresian)) of [Wyoming](/source/Wyoming), USA ([Fossil Butte](/source/Fossil_Butte_National_Monument) of [Green River Formation](/source/Green_River_Formation)) (=†*Paramiatus gurleyi* Romer & Fryxell, 1928)

- †***C. ignotus*** ([Blainville](/source/Henri_Marie_Ducrotay_de_Blainville), 1818) - late Eocene ([Priabonian](/source/Priabonian)) of France ([Montmartre](/source/Montmartre)) (=†"*Amia*" *ignota* Blainville, 1818)

- †***C. macrocephalus*** [Reuss](/source/Adolph_Reuss), 1844 - middle-late Eocene of the [Czech Republic](/source/Czech_Republic) (Kutschlin)

- †***C. oligocenicus*** [Winkler](/source/Tiberius_Cornelis_Winkler), 1880 - early Oligocene ([Rupelian](/source/Rupelian)) of Germany (Sieblos)

- †***C. orientalis*** [Chang](/source/Meemann_Chang), Wang & Wu, 2010 - early-mid Eocene of [Hunan](/source/Hunan), China ([Xiawanpu Formation](https://en.wikipedia.org/w/index.php?title=Xiawanpu_Formation&action=edit&redlink=1))[7]

- †***C. kehreri*** (Andreae, 1893) - middle Eocene ([Lutetian](/source/Lutetian)) of Germany ([Messel Formation](/source/Messel_Formation) & [Geiseltal Formation](https://en.wikipedia.org/w/index.php?title=Geiseltal_Formation&action=edit&redlink=1)) (=*Amia kehreri* Andreae, 1893)

- †***C. valenciennesi*** [Agassiz](/source/Louis_Agassiz), 1844 - late Paleocene of France ([Puy de Dôme](/source/Puy_de_D%C3%B4me) of [Menat Formation](/source/Menat_Formation)). Named for [Achille Valenciennes](/source/Achille_Valenciennes).

Fossils of *C. kehreri* are abundant in the [Messel Formation](/source/Messel_Formation)

The species †*C.* "*lacus*" (Russell, 1928) (=†*Stylomyleodon lacus* Russell, 1928) from the middle Paleocene of Alberta, †*C.* "*chinzhalensis*" (Sytchevskaya, 1986) (=†*Amia chinzhalensis* Sytchevskaya, 1986) from the mid-late Eocene of [Kazakhstan](/source/Kazakhstan), and †*C.* "*russelli*" (Janot, 1966) (=†"*Amia*" *russelli* Janot, 1966) from the late Paleocene of France are considered *[nomina dubia](/source/Nomen_dubium)* due to insufficiently diagnostic remains. The Geiseltal specimens of *C. kehreri* differ morphologically from the Messel ones, and may represent a distinct species.[3] Indeterminate *Cyclurus* remains are known from the middle Eocene of [Jilin](/source/Jilin), China, the late Paleocene [Ravenscrag Formation](/source/Ravenscrag_Formation) of [Saskatchewan](/source/Saskatchewan) & the Maastrichtian [Horseshoe Canyon Formation](/source/Horseshoe_Canyon_Formation) of Alberta, Canada, and possibly the Campanian-aged [Aguja Formation](/source/Aguja_Formation) of [Texas](/source/Texas), USA.[8][9][10][11]

## Paleoecology

*C. gurleyi* is one of the rarest fish of the [Green River Formation](/source/Green_River_Formation)

*C. kehreri* is the most common fossil fish known from the [Messel pit](/source/Messel_pit), and in fact the most abundant fossil [amiid](/source/Amiidae) in the world, with thousands of specimens recovered. Fossils of *C. kehreri* are known representing different growth stages. Almost no specimens of *C. kehreri* are known with fish bones in their stomach (a specimen with [percoid](/source/Percoidei) bones in its stomach is thought to have likely scavenged on them), suggesting that unlike other amiids, *Cyclurus* likely fed on small invertebrates instead of other fish. However, more recently, two *C. kehreri* specimens have been discovered with specimens of the [bat](/source/Bat) *[Palaeochiropteryx](/source/Palaeochiropteryx)* caught in their mouths, suggesting that they either opportunistically attacked the dying bats or attempted scavenging on them, although these attempts were unsuccessful.[12]

Contrasting with *C. kehreri*'s abundance, *C. gurleyi* is one of the rarest fishes from the [Green River Formation](/source/Green_River_Formation), with only 8 specimens known from the hundreds of thousands of fossil fishes excavated.[3]

## References

1. ^ [***a***](#cite_ref-:0_1-0) [***b***](#cite_ref-:0_1-1) ["PBDB Taxon"](https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=109019). *paleobiodb.org*. Retrieved 2024-07-19.

1. ^ [***a***](#cite_ref-:1_2-0) [***b***](#cite_ref-:1_2-1) [***c***](#cite_ref-:1_2-2) [***d***](#cite_ref-:1_2-3) Brownstein, Chase Doran; Near, Thomas J (2024-04-29). ["A giant bowfin from a Paleocene hothouse ecosystem in North America"](https://doi.org/10.1093/zoolinnean/zlae042). *Zoological Journal of the Linnean Society*. **202** (4) zlae042. [doi](/source/Doi_(identifier)):[10.1093/zoolinnean/zlae042](https://doi.org/10.1093%2Fzoolinnean%2Fzlae042). [ISSN](/source/ISSN_(identifier)) [0024-4082](https://search.worldcat.org/issn/0024-4082).

1. ^ [***a***](#cite_ref-:2_3-0) [***b***](#cite_ref-:2_3-1) [***c***](#cite_ref-:2_3-2) [***d***](#cite_ref-:2_3-3) Grande, Lance; Bemis, William E. (1998-04-10). ["A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy. an Empirical Search for Interconnected Patterns of Natural History"](https://www.tandfonline.com/doi/full/10.1080/02724634.1998.10011114). *Journal of Vertebrate Paleontology*. **18** (sup1): 1–696. [Bibcode](/source/Bibcode_(identifier)):[1998JVPal..18S...1G](https://ui.adsabs.harvard.edu/abs/1998JVPal..18S...1G). [doi](/source/Doi_(identifier)):[10.1080/02724634.1998.10011114](https://doi.org/10.1080%2F02724634.1998.10011114). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634).

1. **[^](#cite_ref-4)** Brinkman, Donald B.; Newbrey, Michael G.; Neuman, Andrew G. (2014), ["Diversity and paleoecology of actinopterygian fish from vertebrate microfossil localities of the Maastrichtian Hell Creek Formation of Montana"](https://dx.doi.org/10.1130/2014.2503(09)), *Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas*, Geological Society of America, [doi](/source/Doi_(identifier)):[10.1130/2014.2503(09)](https://doi.org/10.1130%2F2014.2503%2809%29), [ISBN](/source/ISBN_(identifier)) [978-0-8137-2503-1](https://en.wikipedia.org/wiki/Special:BookSources/978-0-8137-2503-1), retrieved 2024-07-19{{[citation](https://en.wikipedia.org/wiki/Template:Citation)}}: CS1 maint: work parameter with ISBN ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_work_parameter_with_ISBN))

1. **[^](#cite_ref-5)** ["PBDB Taxon"](https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=149615). *paleobiodb.org*. Retrieved 2024-07-19.

1. **[^](#cite_ref-6)** Hoganson, John W.; Erickson, J. Mark; Holland Jr., F. D. (2019). ["CHONDRICHTHYAN AND OSTEICHTHYAN PALEOFAUNAS FROM THE CRETACEOUS (LATE MAASTRICHTIAN) FOX HILLS FORMATION OF NORTH DAKOTA, USA: PALEOECOLOGY, PALEOGEOGRAPHY, AND EXTINCTION"](https://bap.priweb2.org/downloads/pubs/item_abstract_5830.pdf) (PDF). *Bulletins of American Paleontology*. **398**. [doi](/source/Doi_(identifier)):[10.32857/bap.2019.398](https://doi.org/10.32857%2Fbap.2019.398) (inactive 11 July 2025).{{[cite journal](https://en.wikipedia.org/wiki/Template:Cite_journal)}}: CS1 maint: DOI inactive as of July 2025 ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_DOI_inactive_as_of_July_2025))

1. **[^](#cite_ref-7)** CHANG Mee-Mann, WANG Ning (2010-06-15). ["DISCOVERY OF †CYCLURUS (AMIINAE, AMIIDAE, AMIIFORMES, PISCES) FROM CHINA"](https://www.researchgate.net/publication/272027051). *Vertebrata PalAsiatica*. **48** (2): 85. [ISSN](/source/ISSN_(identifier)) [2096-9899](https://search.worldcat.org/issn/2096-9899).

1. **[^](#cite_ref-8)** Gaudant, Jean; Schaal, Stephan F. K.; Wei, Sun (2012-12-01). ["A short account on the Eocene fish fauna from Huadian (Jilin Province, China)"](https://doi.org/10.1007/s12549-012-0094-4). *Palaeobiodiversity and Palaeoenvironments*. **92** (4): 417–423. [Bibcode](/source/Bibcode_(identifier)):[2012PdPe...92..417G](https://ui.adsabs.harvard.edu/abs/2012PdPe...92..417G). [doi](/source/Doi_(identifier)):[10.1007/s12549-012-0094-4](https://doi.org/10.1007%2Fs12549-012-0094-4). [ISSN](/source/ISSN_(identifier)) [1867-1608](https://search.worldcat.org/issn/1867-1608).

1. **[^](#cite_ref-9)** Sinha, Sinjini; Brinkman, Donald B.; Murray, Alison M.; Krause, David W. (2021-05-04). ["Late Paleocene fishes of the Ravenscrag Formation, Roche Percée area, southeastern Saskatchewan, Canada"](https://www.tandfonline.com/doi/full/10.1080/02724634.2021.1957907). *Journal of Vertebrate Paleontology*. **41** (3) e1957907. [Bibcode](/source/Bibcode_(identifier)):[2021JVPal..41E7907S](https://ui.adsabs.harvard.edu/abs/2021JVPal..41E7907S). [doi](/source/Doi_(identifier)):[10.1080/02724634.2021.1957907](https://doi.org/10.1080%2F02724634.2021.1957907). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634).

1. **[^](#cite_ref-10)** Larson, Derek W.; Brinkman, Donald B.; Bell, Phil R. (2010). Sues, Hans-Deiter (ed.). ["Faunal assemblages from the upper Horseshoe Canyon Formation, an early Maastrichtian cool-climate assemblage from Alberta, with special reference to the Albertosaurus sarcophagus bonebedThis article is one of a series of papers published in this Special Issue on the theme Albertosaurus "](http://www.nrcresearchpress.com/doi/10.1139/E10-005). *Canadian Journal of Earth Sciences*. **47** (9): 1159–1181. [doi](/source/Doi_(identifier)):[10.1139/E10-005](https://doi.org/10.1139%2FE10-005). [ISSN](/source/ISSN_(identifier)) [0008-4077](https://search.worldcat.org/issn/0008-4077).

1. **[^](#cite_ref-11)** Wick, Steven L.; Brink, Alyson A. (2022-11-01). ["A new non-marine osteichthyan fauna from the Upper Cretaceous (Campanian) of West Texas: Additional evidence for latitudinal segregation among bony fish in the Western Interior"](https://www.sciencedirect.com/science/article/pii/S019566712200163X). *Cretaceous Research*. **139** 105299. [Bibcode](/source/Bibcode_(identifier)):[2022CrRes.13905299W](https://ui.adsabs.harvard.edu/abs/2022CrRes.13905299W). [doi](/source/Doi_(identifier)):[10.1016/j.cretres.2022.105299](https://doi.org/10.1016%2Fj.cretres.2022.105299). [ISSN](/source/ISSN_(identifier)) [0195-6671](https://search.worldcat.org/issn/0195-6671).

1. **[^](#cite_ref-12)** Vullo, Romain; Frey, Eberhard (2024). ["Bat consumption by holostean fishes in the Eocene Lake Messel: insights into the trophic adaptability of extinct gars and bowfins"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11371436). *Biology Letters*. **20** (9) 20240194. [doi](/source/Doi_(identifier)):[10.1098/rsbl.2024.0194](https://doi.org/10.1098%2Frsbl.2024.0194). [ISSN](/source/ISSN_(identifier)) [1744-9561](https://search.worldcat.org/issn/1744-9561). [PMC](/source/PMC_(identifier)) [11371436](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11371436). [PMID](/source/PMID_(identifier)) [39226920](https://pubmed.ncbi.nlm.nih.gov/39226920).

Taxon identifiers Cyclurus Wikidata: Q17628456 EoL: 4653362 Paleobiology Database: 109019

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Adapted from the Wikipedia article [Cyclurus](https://en.wikipedia.org/wiki/Cyclurus) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Cyclurus?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.