Cyclurus

{{Automatic taxobox

| fossil_range = {{fossil range|70|30|earliest=Campanian|Maastrichtian to Rupelian}} Possible Campanian occurrence

| image = Cyclurus kehreri 001.jpg

| image_caption = Fossil of C. kehreri

| taxon = Cyclurus

| authority = Agassiz, 1844

| type_species = {{extinct}}Cyclurus valenciennesi

| type_species_authority = Agassiz, 1844

| subdivision_ranks = Species

| subdivision = See text

| synonyms = * {{extinct}}Kindleia Jordan, 1927

{{extinct}}Paramiatus Romer & Fryxell, 1928
{{extinct}}Stylomyleodon Russell, 1928

}}

Cyclurus (Ancient Greek for "rounded tail") is an extinct genus of freshwater amiid ray-finned fish known from the Late Cretaceous to the Early Oligocene across much of the Northern Hemisphere.{{Cite web |title=PBDB Taxon |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=109019 |access-date=2024-07-19 |website=paleobiodb.org}} It is thought to be the closest relative of the extant bowfins in the genus Amia, although species of Cyclurus were significantly smaller in size compared to Amia.{{Cite journal |last1=Brownstein |first1=Chase Doran |last2=Near |first2=Thomas J |date=2024-04-29 |title=A giant bowfin from a Paleocene hothouse ecosystem in North America |url=https://doi.org/10.1093/zoolinnean/zlae042 |journal=Zoological Journal of the Linnean Society |doi=10.1093/zoolinnean/zlae042 |issn=0024-4082|url-access=subscription }}

Evolution

Remains of Cyclurus are first known from western North America during the Maastrichtian stage of the Cretaceous with the species C. fragosus, with the genus having presumably diverged from Amia shortly before. Potential earlier remains are known from the Campanian. Alongside Amia, Cyclurus survived the Cretaceous-Paleogene extinction event in a refugium in western North America. Shortly afterwards, it saw a dramatic range expansion over the Paleogene, colonizing Europe and Asia by the Late Paleocene and becoming particularly successful and speciose in Europe. By the Late Eocene, it was one of the last two surviving halecomorph genera, alongside Amia. However, alongside most Amia species aside from those in eastern North America, it became extinct during the Oligocene.{{Cite journal |last1=Grande |first1=Lance |last2=Bemis |first2=William E. |date=1998-04-10 |title=A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy. an Empirical Search for Interconnected Patterns of Natural History |url=https://www.tandfonline.com/doi/full/10.1080/02724634.1998.10011114 |journal=Journal of Vertebrate Paleontology |language=en |volume=18 |issue=sup1 |pages=1–696 |doi=10.1080/02724634.1998.10011114 |bibcode=1998JVPal..18S...1G |issn=0272-4634|url-access=subscription }}

Taxonomy

The following species are known:

†C. efremovi (Sytchevskaya, 1981) - late Paleocene of Mongolia (Naran Bulak Formation) (=Amia efremovi Sytchevskaya, 1981). Named for Ivan Yefremov.
†C. fragosus (Jordan, 1927) - Late Cretaceous (Maastrichtian) of Alberta, Canada (Scollard Formation) and Montana, North Dakota, South Dakota and Wyoming, USA (Hell Creek Formation, Fox Hills Formation) (=Kindleia fragosa Jordan, 1927){{Citation |last1=Brinkman |first1=Donald B. |title=Diversity and paleoecology of actinopterygian fish from vertebrate microfossil localities of the Maastrichtian Hell Creek Formation of Montana |date=2014 |work=Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas |url=http://dx.doi.org/10.1130/2014.2503(09) |access-date=2024-07-19 |publisher=Geological Society of America |isbn=978-0-8137-2503-1 |last2=Newbrey |first2=Michael G. |last3=Neuman |first3=Andrew G.|doi=10.1130/2014.2503(09) |url-access=subscription }}{{Cite web |title=PBDB Taxon |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=149615 |access-date=2024-07-19 |website=paleobiodb.org}}{{Cite journal |last1=Hoganson |first1=John W. |last2=Erickson |first2=J. Mark |last3=Holland Jr. |first3=F. D. |date=2019 |title=CHONDRICHTHYAN AND OSTEICHTHYAN PALEOFAUNAS FROM THE CRETACEOUS (LATE MAASTRICHTIAN) FOX HILLS FORMATION OF NORTH DAKOTA, USA: PALEOECOLOGY, PALEOGEOGRAPHY, AND EXTINCTION |url=https://bap.priweb2.org/downloads/pubs/item_abstract_5830.pdf |journal=Bulletins of American Paleontology |volume=398 |doi=10.32857/bap.2019.398|doi-broken-date=1 November 2024 }}
†C. gurleyi (Romer & Fryxell, 1928) - early Eocene (Ypresian) of Wyoming, USA (Fossil Butte of Green River Formation) (=†Paramiatus gurleyi Romer & Fryxell, 1928)
†C. ignotus (Blainville, 1818) - late Eocene (Priabonian) of France (Montmartre) (=†"Amia" ignota Blainville, 1818)
†C. macrocephalus Reuss, 1844 - middle-late Eocene of the Czech Republic (Kutschlin)
†C. oligocenicus Winkler, 1880 - early Oligocene (Rupelian) of Germany (Sieblos)
†C. orientalis Chang, Wang & Wu, 2010 - early-mid Eocene of Hunan, China (Xiawanpu Formation){{Cite journal |last=CHANG Mee-Mann |first=WANG Ning |date=2010-06-15 |title=DISCOVERY OF †CYCLURUS (AMIINAE, AMIIDAE, AMIIFORMES, PISCES) FROM CHINA |url=https://www.researchgate.net/publication/272027051 |journal=Vertebrata PalAsiatica |language=en |volume=48 |issue=2 |pages=85 |issn=2096-9899}}
†C. kehreri (Andreae, 1893) - middle Eocene (Lutetian) of Germany (Messel Formation & Geiseltal Formation) (=Amia kehreri Andreae, 1893)
†C. valenciennesi Agassiz, 1844 - late Paleocene of France (Puy de Dôme of Menat Formation). Named for Achille Valenciennes.

File:Cyclurus kehreri 5676.jpg|left]]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, and †C. "russelli" (Janot, 1966) (=†"Amia" russelli Janot, 1966) from the late Paleocene of France are considered nomina dubia due to insufficiently diagnostic remains. The Geiseltal specimens of C. kehreri differ morphologically from the Messel ones, and may represent a distinct species. Indeterminate Cyclurus remains are known from the middle Eocene of Jilin, China, the late Paleocene Ravenscrag Formation of Saskatchewan & the Maastrichtian Horseshoe Canyon Formation of Alberta, Canada, and possibly the Campanian-aged Aguja Formation of Texas, USA.{{Cite journal |last1=Gaudant |first1=Jean |last2=Schaal |first2=Stephan F. K. |last3=Wei |first3=Sun |date=2012-12-01 |title=A short account on the Eocene fish fauna from Huadian (Jilin Province, China) |url=https://doi.org/10.1007/s12549-012-0094-4 |journal=Palaeobiodiversity and Palaeoenvironments |language=en |volume=92 |issue=4 |pages=417–423 |doi=10.1007/s12549-012-0094-4 |bibcode=2012PdPe...92..417G |issn=1867-1608|url-access=subscription }}{{Cite journal |last1=Sinha |first1=Sinjini |last2=Brinkman |first2=Donald B. |last3=Murray |first3=Alison M. |last4=Krause |first4=David W. |date=2021-05-04 |title=Late Paleocene fishes of the Ravenscrag Formation, Roche Percée area, southeastern Saskatchewan, Canada |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2021.1957907 |journal=Journal of Vertebrate Paleontology |language=en |volume=41 |issue=3 |doi=10.1080/02724634.2021.1957907 |bibcode=2021JVPal..41E7907S |issn=0272-4634|url-access=subscription }}{{Cite journal |last1=Larson |first1=Derek W. |last2=Brinkman |first2=Donald B. |last3=Bell |first3=Phil R. |date=2010 |editor-last=Sues |editor-first=Hans-Deiter |title=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 . |url=http://www.nrcresearchpress.com/doi/10.1139/E10-005 |journal=Canadian Journal of Earth Sciences |language=en |volume=47 |issue=9 |pages=1159–1181 |doi=10.1139/E10-005 |issn=0008-4077|url-access=subscription }}{{Cite journal |last1=Wick |first1=Steven L. |last2=Brink |first2=Alyson A. |date=2022-11-01 |title=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 |url=https://www.sciencedirect.com/science/article/pii/S019566712200163X |journal=Cretaceous Research |volume=139 |pages=105299 |doi=10.1016/j.cretres.2022.105299 |bibcode=2022CrRes.13905299W |issn=0195-6671|url-access=subscription }}

Paleoecology

File:Cyclurus gurleyi FOBU.jpg]]

C. kehreri is the most common fossil fish known from the Messel pit, and in fact the most abundant fossil amiid 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 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 Palaeochiropteryx caught in their mouths, suggesting that they either opportunistically attacked the dying bats or attempted scavenging on them, although these attempts were unsuccessful.{{Cite journal |last1=Vullo |first1=Romain |last2=Frey |first2=Eberhard |date=2024 |title=Bat consumption by holostean fishes in the Eocene Lake Messel: insights into the trophic adaptability of extinct gars and bowfins |journal=Biology Letters |language=en |volume=20 |issue=9 |doi=10.1098/rsbl.2024.0194 |issn=1744-9561 |pmc=11371436 |pmid=39226920|pmc-embargo-date=September 4, 2025 }}

Contrasting with C. kehreri's abundance, C. gurleyi is one of the rarest fishes from the Green River Formation, with only 8 specimens known from the hundreds of thousands of fossil fishes excavated.

Cyclurus

Evolution

Taxonomy

Paleoecology

References