View source for Biology:Chimaera

{{Short description|Cartilaginous fish in the order Chimaeriformes}}
{{Automatic taxobox
| name = Chimaeras
| fossil_range = {{Fossil range|Early Carboniferous|Present}}
| image = Hydrolagus colliei.jpg
| image_caption = ''Hydrolagus colliei'' ([[Biology:Chimaeridae|Chimaeridae]])
| taxon = Chimaeriformes
| authority = Obruchev, 1953
| subdivision_ranks = Subgroups
| subdivision = *†''[[Biology:Echinochimaera|Echinochimaera]]''
*†''[[Biology:Protochimaera|Protochimaera]]''
*†''[[Biology:Squaloraja|Squaloraja]]''
*†Myriacanthoidei
*'''Chimaeroidei'''
**[[Biology:Callorhinchidae|Callorhinchidae]]
**[[Biology:Chimaeridae|Chimaeridae]]
**[[Biology:Rhinochimaeridae|Rhinochimaeridae]]
}}

'''Chimaeras'''<ref name=FB/> are cartilaginous fish in the [[Biology:Order|order]] '''Chimaeriformes''' {{IPAc-en|k|ᵻ|'|m|E|r|ᵻ|f|ɔr|m|iː|z}}, known informally as '''ghost sharks''', '''rat fish''', '''spookfish''', or '''rabbit fish'''; the last three names are not to be confused with rattails, [[Biology:Barreleye|Opisthoproctidae]], or [[Biology:Rabbitfish|Siganidae]], respectively.

At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are [[Biology:Shark|shark]]s and rays, though their last common ancestor with them lived nearly 400 million years ago.<ref name="scidai09">{{cite web |title=Ancient And Bizarre Fish Discovered: New Species Of Ghostshark From California And Baja California |url=https://www.sciencedaily.com/releases/2009/09/090922095816.htm |publisher=ScienceDaily |date=September 23, 2009 |access-date=2009-09-23}}</ref> Living species are largely confined to deep water.<ref name="PetersonEschmeyer1999">{{cite book |last1=Peterson |first1=Roger Tory |last2=Eschmeyer |first2=William N. |last3=Herald |first3=Earl S. |title=A Field Guide to Pacific Coast Fishes: North America |url=https://books.google.com/books?id=h_6RNzCo6lAC&pg=PA13 |access-date=9 August 2015 |date=1 September 1999 |publisher=Houghton Mifflin Harcourt |isbn=0-618-00212-X |page=13}}</ref>

==Anatomy==
[[File:Deep sea chimaera.jpg|thumb|left|Deep-sea chimaera photographed by the NOAAS Okeanos Explorer. Visible on its snout are tiny pores which lead to electroreceptor cells.]]

Chimaeras are soft-bodied, shark-like fish with bulky heads and long, tapered tails; measured from the tail, they can grow up to {{convert|150|cm|ft|abbr=on}} in length. Like other members of the class Chondrichthyes, chimaera skeletons are entirely cartilaginous, or composed of [[Biology:Cartilage|cartilage]]. Their skin is smooth and relatively free of scales or unique features, lacking the keeled, tooth-like placoid scales (denticles) present on sharks and rays. However, there are still exceptions, as hatchlings retain a few rows of denticles on the back, and adult males bear denticulated sexual organs.<ref name=":1">{{Citation |last1=Didier |first1=Dominique |title=Phylogeny, Biology and Classification of Extant Holocephalans |date=2012-04-09 |url=https://www.researchgate.net/publication/259294130 |work=Biology of Sharks and Their Relatives, Second Edition |volume=20123460 |pages=97–122 |editor-last=Carrier |editor-first=Jeffrey |publisher=CRC Press |language=en |doi=10.1201/b11867-6 |isbn=978-1-4398-3924-9 |access-date= |last2=Kemper |first2=Jenny |last3=Ebert |first3=David |editor2-last=Musick |editor2-first=John |editor3-last=Heithaus |editor3-first=Michael}}</ref> The [[Biology:Branchial arch|gill arches]] are condensed into a pouch-like bundle covered by a sheet of skin (an [[Biology:Operculum (fish)|operculum]]), with a single [[Biology:Gill|gill]]-opening in front of the pectoral fins.<ref name="EoF" />

The pectoral fins are large enough to generate lift and a relaxed forward momentum, giving the chimaera the appearance of "flying" through the water. Further back on the body are also a pair of smaller [[Biology:Pelvic fin|pelvic fins]], and some genera bear an anal fin in front of the tail. In [[Biology:Chimaeridae|chimaerids]] and [[Biology:Rhinochimaeridae|rhinochimaerids]], the tail is leptocercal, meaning that it is thin and whip-like, edged from above and below by fins of similar size. In [[Biology:Callorhinchus|callorhinchids]], the tail is instead heterocercal, with a larger upper lobe inclined upwards, similar to many sharks. There are two dorsal fins: a large triangular first dorsal fin and a low rectangular or depressed second dorsal fin. For defense, some chimaeras have a [[Biology:Venom|venom]]ous spine on the front edge of the dorsal fin.<ref name=":1" />

In many species, the bulbous snout is modified into an elongated sensory organ, capable of [[Philosophy:Electroreception and electrogenesis|electroreception]] to find prey.<ref name="EoF">{{cite book |author1-last=Stevens |author1-first=John |author2-last=Last |author2-first=Peter R. |editor1-last=Paxton |editor1-first=John R. |editor2-last=Eschmeyer |editor2-first=William N. |year=1998 |title=Encyclopedia of Fishes |publisher=Academic Press |location=San Diego |page=69 |isbn=0-12-547665-5}}</ref><ref name="BullockHartline2012">{{cite book |author1-last=Bullock |author1-first=T. H. |author2-last=Hartline |author2-first=R. H. |author3-last=Kalmijn |author3-first=A. J. |author4-last=Laurent |author4-first=P. |author5-last=Murray |author5-first=R. W. |author6-last=Scheich |author6-first=H. |author7-last=Schwartz |author7-first=E. |author8-last=Szabo |author8-first=T. |editor-last=Fessard |editor-first=A. |title=Electroreceptors and Other Specialized Receptors in Lower Vertebrates |url=https://books.google.com/books?id=wq3tCAAAQBAJ&pg=PA125 |date=6 December 2012 |publisher=Springer Science & Business Media |page=125 |isbn=978-3-642-65926-3}}</ref> The cartilaginous skull is holostylic, meaning that the [[Biology:Palatoquadrate|palatoquadrate]] (upper jaw cartilage) is completely fused to the [[Medicine:Neurocranium|neurocranium]] (cranial cartilage). This contrasts with modern sharks, where the palatoquadrate is movable and detachable, a trait known as hyostyly. The back of the head is supported by a complex of fused vertebrae called the synarcual, which also connects to the dorsal fin spine.<ref name=":1" />

Instead of sharks' many sharp, consistently-replaced teeth, chimaeras have just six large, permanent tooth-plates, which grow continuously throughout their entire life. These tooth-plates are arranged in three pairs, with one pair at the tip of the lower jaws and two pairs along the upper jaws. They together form a protruding, beak-like crushing and grinding mechanism, comparable to the incisor teeth of [[Biology:Rodent|rodents]] and [[Biology:Lagomorpha|lagomorphs]] (hence the name "rabbit fish").<ref name=":1" /> Chimaera teeth are unique among vertebrates, due to their mode of mineralization. Most of each plate is formed by relatively soft [[Biology:Dentin|osteodentin]], but the active edges are supplemented by a unique hypermineralized [[Biology:Tissue|tissue]] called pleromin. Pleromin is an extremely hard [[Biology:Tooth enamel|enamel]]-like tissue, arranged into sheets or beaded rods, but it is deposited by mesenchyme-derived cells similar to those that form [[Biology:Bone|bone]]. In addition, pleuromin's hardness is due to the mineral [[Chemistry:Whitlockite|whitlockite]], which crystalizes within the teeth as the animal matures. Other vertebrates with hypermineralized teeth rely on enamel, which is derived from [[Biology:Ameloblast|ameloblasts]] and encases round crystals of the mineral [[Chemistry:Apatite|apatite]].<ref>{{Cite journal |last1=Iijima |first1=Mayumi |last2=Ishiyama |first2=Mikio |date=2020-10-29 |title=A unique mineralization mode of hypermineralized pleromin in the tooth plate of Chimaera phantasma contributes to its microhardness |journal=Scientific Reports |language=en |volume=10 |issue=1 |pages=18591 |doi=10.1038/s41598-020-75545-0 |pmid=33122684 |pmc=7596707 |issn=2045-2322}}</ref>

Chimaeras also differ from sharks in that they have separate [[Biology:Anus|anal]] and urogenital openings.

== Behavior ==
Chimaeras live in temperate ocean floors down to {{convert|2600|m|ft|abbr=on}} deep, with few occurring at depths shallower than {{convert|200|m|ft|abbr=on}}. Exceptions include the members of the [[Biology:Genus|genus]] ''[[Biology:Callorhinchus|Callorhinchus]]'', the rabbit fish and the [[Biology:Spotted ratfish|spotted ratfish]], which locally or periodically can be found at shallower depths. Consequently, these are also among the few species from the chimaera order kept in public aquaria.<ref>{{cite book |last1=Tozer |first1=Helen |last2=Dagit |first2=Dominique D. |year=2004 |chapter=Chapter 33: Husbandry of Spotted Ratfish, ''Hydrolagus colliei'' |chapter-url=https://02af4cce-a-62cb3a1a-s-sites.googlegroups.com/site/elasmobranchhusbandry/Chapter33-HusbandryofSpottedRatfish.pdf |editor1-last=Smith |editor1-first=Mark |editor2-last=Warmolts |editor2-first=Doug |editor3-last=Thoney |editor3-first=Dennis |editor4-last=Heuter |editor4-first=Robert |title=Elasmobranch Husbandry Manual: Captive Care of Sharks, Rays, and their Relatives |publisher=Ohio Biological Survey |pages=487–491 |isbn=0-86727-152-3 }}{{Dead link|date=July 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> They live in all the oceans except for the Arctic and Antarctic oceans.

=== Diet ===
The usual diet of chimaeras consist of [[Biology:Crustacean|crustaceans]], and more specifically, they include ophiurans and molluscs.<ref>{{Cite journal |last1=García-Salinas |first1=Pablo |last2=Gallego |first2=Victor |last3=Asturiano |first3=Juan F. |date=August 2021 |title=Reproductive Anatomy of Chondrichthyans: Notes on Specimen Handling and Sperm Extraction. II. Sharks and Chimaeras |journal=Animals |language=en |volume=11 |issue=8 |pages=2191 |doi=10.3390/ani11082191 |issn=2076-2615 |pmc=8388383 |pmid=34438648 |doi-access=free }}</ref> Modern species are demersal [[Biology:Durophagy|durophages]], but they used to be more diverse. The Carboniferous period had forms that lived as specialised suction feeders in the water column.<ref>{{Cite journal |url=https://pnas.org/doi/10.1073/pnas.2207854119 |title=Evidence for high-performance suction feeding in the Pennsylvanian stem-group holocephalan Iniopera |first1=Richard P. |last1=Dearden |first2=Anthony |last2=Herrel |first3=Alan |last3=Pradel |date=January 24, 2023 |journal=Proceedings of the National Academy of Sciences |volume=120 |issue=4 |via=CrossRef |doi=10.1073/pnas.2207854119 |pmid=36649436 |pmc=9942859}}</ref>

=== Reproduction ===
Chimaera reproduction resembles that of sharks in some ways: males employ [[Biology:Clasper|claspers]] for internal fertilization of females and females lay eggs within spindle-shaped, leathery [[Biology:Egg case (Chondrichthyes)|egg cases]].<ref name="FB">{{FishBase order |order=Chimaeriformes |year=2014 |month=November}}</ref>

Unlike sharks, male chimaeras have retractable sexual appendages (known as tentacula) to assist mating.<ref>{{cite magazine |last=Madrigal |first=Alexis |date=22 September 2009 |title=Freaky New Ghostshark ID'd Off California Coast |url=https://www.wired.com/2009/09/ghostshark/ |magazine=Wired |access-date=14 November 2018 |quote=...&nbsp;Perhaps the most intriguing feature of the newly described species, ''Hydrolagus melanophasma'', is a presumed sexual organ that extends from its forehead called a tentaculum.&nbsp;...}}</ref><ref name="EoF" /> The frontal tentaculum, a bulbous rod which extends out of the forehead, is used to clutch the females' pectoral fins during mating. The prepelvic tentacula are serrated hooked plates normally hidden in pouches in front of the pelvic fins, and they anchor the male to the female. Lastly, the pelvic claspers (sexual organs shared by sharks) are fused together by a cartilaginous sheathe before splitting into a pair of flattened lobes at their tip.<ref name=":1" />

=== Parasites ===
As other fish, chimaeras have a number of parasites. ''[[Biology:Chimaericola leptogaster|Chimaericola leptogaster]]'' ([[Biology:Chimaericolidae|Chimaericolidae]]) is a [[Biology:Monogenea|monogenea]]n parasite of the [[Biology:Gill|gill]]s of ''Chimaera monstrosa''; the species can attain {{convert|50|mm|in|abbr=on}} in length.

== Conservation and threats ==
Despite their secluded habits, some chimaera species may be threatened by overfishing through bycatch or commercial exploitation. No species are listed as [[Biology:Endangered species (IUCN status)|Endangered]] according to the [[Organization:International Union for Conservation of Nature|IUCN]], but four are listed as [[Biology:Vulnerable species|Vulnerable]], four more as [[Biology:Near-threatened species|Near Threatened]], and many more as [[Biology:Data deficient|Data Deficient]] (too rare to evaluate). Many species have restricted ranges and practically none have had their movement patterns studied. In addition, bycatch reports are usually insufficiently precise to the species or even genus level, so it is difficult to keep track of bycatch on a species-by-species basis. This lack of data renders chimaera species especially susceptible to overlooked population declines.<ref name=":2">{{Cite journal |last1=Finucci |first1=Brittany |last2=Cheok |first2=Jessica |last3=Ebert |first3=David A. |last4=Herman |first4=Katelyn |last5=Kyne |first5=Peter M. |last6=Dulvy |first6=Nicholas K. |date=2021 |title=Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks |url=https://onlinelibrary.wiley.com/doi/10.1111/faf.12526 |journal=Fish and Fisheries |language=en |volume=22 |issue=2 |pages=391–412 |doi=10.1111/faf.12526 |s2cid=229433827 |issn=1467-2960}}</ref>

Several near-shore species are purposefully caught for their meat, especially callorhinchids, ''Hydrolagus bemisi'' ([[Biology:Pale ghost shark|pale ghost shark]]), and ''Hydrolagus novaezealandi''ae ([[Biology:Dark ghostshark|dark ghost shark]]). Modern quotas have helped to moderate collection of these species to a sustainable level, though ''Callorhinchus milii'' (the [[Biology:Australian ghostshark|Australian ghostshark]]) experienced severe overfishing in the 20th century before protections were enacted. ''Neoharriotta pinnata'' ([[Biology:Sicklefin chimaera|sicklefin chimaera]]) is targeted along the coast of {{wipe|India}} for its liver oil, and a recent decline of catch rates may indicate a population crash. Even species without commercial exploitation can fall victim to bycatch: ''Callorhinchus callorynchus'' (American elephantfish), ''Neoharriotta carri'' ([[Biology:Dwarf sicklefin chimaera|dwarf sicklefin chimaera]]), ''Chimaera monstrosa'' ([[Biology:Rabbit fish|rabbit fish]]), ''Chimaera ogilbyi'' ([[Biology:Ogilby's ghostshark|Ogilby's ghostshark]]), ''Hydrolagus colliei'' ([[Biology:Spotted ratfish|spotted ratfish]]), and ''Hydrolagus melanophasma'' (eastern Pacific black ghostshark) all have bycatch rates exceeding 10% in certain parts of their range, and some are experiencing steep declines. Chimaeras have mostly avoided harvesting for the fin trade, which threatens many true sharks.<ref name=":2" />

Another threat is habitat destruction of coastal nurseries (by urban development) or deepwater reefs (by [[Earth:Deep sea mining|deep sea mining]] and trawling). Near-shore species such as ''Callorhinchus milii'' are vulnerable to the effects of [[Earth:Climate change|climate change]]: stronger storms and warmer seawater are predicted to increase egg mortality by disrupting the stable environments necessary to complete incubation.<ref name=":2" />

==Classification==
{{Main articles|Biology:List of chimaeras}}
[[File:Callorhinchus callorhynchus.JPG|thumb|''[[Biology:Callorhinchus callorynchus|Callorhinchus callorynchus]]'']]
[[File:Chimaera monstrosa.png|thumb|''Chimaera monstrosa'']]
[[File:Hydrolagus affinis.jpg|thumb|''Hydrolagus affinis'']]
[[File:Harriotta raleighana.jpg|thumb|''Harriotta raleighana'']]
In some classifications, the chimaeras are included (as subclass Holocephali) in the class Chondrichthyes of cartilaginous fishes; in other systems, this distinction may be raised to the level of class. Chimaeras also have some characteristics of [[Biology:Osteichthyes|bony fishes]].

A renewed effort to explore deep water and to undertake taxonomic analysis of specimens in museum collections led to a boom during the first decade of the 21st century in the number of new species identified.<ref name="scidai09" /> A preliminary study found 8% of species to be threatened.<ref>{{Cite journal|last1=Finucci|first1=Brittany|last2=Cheok|first2=Jessica|last3=Ebert|first3=David A.|last4=Herman|first4=Katelyn|last5=Kyne|first5=Peter M.|last6=Dulvy|first6=Nicholas K.|title=Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/faf.12526|journal=Fish and Fisheries|year=2021|volume=22|issue=2|pages=391–412|language=en|doi=10.1111/faf.12526|s2cid=229433827|issn=1467-2979}}</ref> There are over 50 extant species in six genera and three families, with other genera known from fossils. The extant species fall into three families—the Callorhinchidae, Rhinochimaeridae and [[Biology:Chimaeridae|Chimaeridae]] with the callorhinchids being the most basal [[Biology:Clade|clade]].

Suborder '''Chimaeroidei''' <small>Patterson 1965</small>
*Family [[Biology:Callorhinchidae|Callorhinchidae]] <small>Garman, 1901</small>
** Genus ''[[Biology:Callorhinchus|Callorhinchus]]'' <small>Lacépède, 1798</small> (3 extant species) Mid-Cretaceous–recent
* Family [[Biology:Chimaeridae|Chimaeridae]] <small>Bonaparte, 1831</small>
** Genus ''[[Biology:Chimaera (genus)|Chimaera]]'' <small>[[Biography:Carl Linnaeus|Linnaeus]], 1758</small> (16 species) Eocene–recent
** Genus ''[[Biology:Hydrolagus|Hydrolagus]]'' <small>Gill, 1863</small> (26 species) Miocene–recent
* Family [[Biology:Rhinochimaeridae|Rhinochimaeridae]] <small>Garman, 1901</small>
** Genus ''[[Biology:Harriotta|Harriotta]]'' <small>[[Biography:George Brown Goode|Goode]] & Bean, 1895</small> (2 species)
** Genus ''[[Biology:Neoharriotta|Neoharriotta]]'' <small>Bigelow & Schroeder, 1950</small> (3 species)
** Genus ''[[Biology:Rhinochimaera|Rhinochimaera]]'' <small>Garman, 1901</small> (3 species)

== Evolution ==
Tracing the evolution of these species has been problematic given the paucity of good fossils. DNA sequencing has become the preferred approach to understanding speciation.<ref>{{cite journal |last1=Inoue |first1=Jun G. |last2=Miya |first2=Masaki |last3=Lam |first3=Kevin |last4=Tay |first4=Boon-Hui |last5=Danks |first5=Janine A. |last6=Bell |first6=Justin |last7=Walker |first7=Terrence I. |last8=Venkatesh |first8=Byrappa |date=November 2010 |title=Evolutionary Origin and Phylogeny of the Modern Holocephalans (Chondrichthyes: Chimaeriformes): A Mitogenomic Perspective |url=https://academic.oup.com/mbe/article/27/11/2576/1121974 |journal=Molecular Biology and Evolution |volume=27 |issue=11 |pages=2576–2586 |doi=10.1093/molbev/msq147 |pmid=20551041 |access-date=14 November 2018 |doi-access=free}}</ref>

The group containing chimaeras and their close relatives ([[Biology:Holocephali|Holocephali]]) is thought to have originated about 420 million years ago during the [[Earth:Silurian|Silurian]]. The oldest known Chimaeriform is ''[[Biology:Protochimaera|Protochimaera]]'' from the Early [[Earth:Carboniferous|Carboniferous]] (338-332 million years ago) of Russia, which is more closely related to modern chimeras (Chimaeroidei) than any other known extinct groups of Chimaeriformes.<ref name=":0">{{Cite journal |last1=Lebedev |first1=Oleg A. |last2=Popov |first2=Evgeny V. |last3=Bagirov |first3=Sergey V. |last4=Bolshiyanov |first4=Igor P. |last5=Kadyrov |first5=Rail I. |last6=Statsenko |first6=Evgeny O. |date=2021-10-21 |title=The earliest chimaeriform fish from the Carboniferous of Central Russia |url=https://doi.org/10.1080/14772019.2021.1977732 |journal=Journal of Systematic Palaeontology |volume=19 |issue=12 |pages=821–846 |doi=10.1080/14772019.2021.1977732 |issn=1477-2019 |s2cid=239509836}}</ref> The earliest known remains attributable to modern chimaeras are known from the Early Jurassic (Pliensbachian) of Europe, but egg cases from the [[Earth:Late Triassic|Late Triassic]] of Yakutia, Russia and New Zealand<ref>{{Cite journal |last1=Gottfried |first1=Michael D. |last2=Fordyce |first2=R. Ewan |date=2015-05-04 |title=A Late Triassic chimaeroid egg capsule from New Zealand: early evidence of chimaeroid reproductive mode from the eastern margin of Gondwana |url=http://www.tandfonline.com/doi/full/10.1080/14772019.2014.880752 |journal=Journal of Systematic Palaeontology |language=en |volume=13 |issue=5 |pages=371–375 |doi=10.1080/14772019.2014.880752 |issn=1477-2019 |s2cid=128402250}}</ref> that resemble those of rhinochimaerids and callorhinchids respectively indicates that they had a global distribution prior to the end of the [[Earth:Triassic|Triassic]]. Unlike modern chimaeras, [[Earth:Mesozoic|Mesozoic]] representatives are often found in shallow water settings.<ref>{{Cite journal |last1=Popov |first1=Evgeny V. |last2=Delsate |first2=Dominique |last3=Felten |first3=Roland |date=2019-07-02 |title=A New Callorhinchid Genus (Holocephali, Chimaeroidei) from the Early Bajocian of Ottange-Rumelange, on the Luxembourg-French Border |url=https://www.researchgate.net/publication/334183749 |journal=Paleontological Research |volume=23 |issue=3 |pages=220 |doi=10.2517/2018PR021 |issn=1342-8144 |s2cid=198423356}}</ref> 

Extinct chimaeriforms include:

*†Genus ''[[Biology:Echinochimaera|Echinochimaera]]'' <small>Lund, 1977</small> United States, Lower Carboniferous (Serpukhovian)
*†Genus ''[[Biology:Protochimaera|Protochimaera]]'' <small>Lebedev & Popov in Lebedev et al., 2021</small> Moscow Region, Russia, Lower Carboniferous (Viséan–Serpukhovian)<ref name=":0" />
*†Genus ''[[Biology:Squaloraja|Squaloraja]]'' Europe, Early Jurassic (Hettangian–Sinemurian)
* †Suborder Myriacanthoidei <small>Patterson 1965</small> (Late Triassic–Late Jurassic)
** †Family Chimaeropsidae
*** †''Chimaeropsis'' <small>Zittel 1887</small> Belgium, Early Jurassic (Sinemurian)
** †Family Myriacanthidae <small>Woodward 1889</small>
*** †''[[Biology:Acanthorhina|Acanthorhina]]'' <small>Fraas 1910</small> [[Earth:Posidonia Shale|Posidonia Shale Formation]], Germany, Early Jurassic (Toarcian)
*** †''[[Biology:Agkistracanthus|Agkistracanthus]]'' <small>Duffin and Furrer 1981</small> Austria, England and Switzerland, Late Triassic–Early Jurassic (Rhaetian–Sinemurian)
*** †''[[Biology:Alethodontus|Alethodontus]]'' <small>Duffin 1983</small> Germany, Early Jurassic (Sinemurian)
*** †''Halonodon'' <small>Duffin 1984</small> Belgium and Luxembourg, Early Jurassic (Sinemurian)
*** †''[[Biology:Metopacanthus|Metopacanthus]]'' <small>Zittel 1887</small> Posidonia Shale Formation, Germany, Early Jurassic (Toarcian)
*** †''Oblidens'' <small>Duffin and Milàn 2017</small> [[Earth:Hasle Formation|Hasle Formation]], Denmark, Early Jurassic (Pliensbachian)
*** †''Myriacanthus'' <small>Agassiz 1837</small> United Kingdom, Late Triassic-Early Jurassic (Rhaetian–Sinemurian)
*** †''Recurvacanthus'' <small>Duffin 1981</small> United Kingdom, Early Jurassic (Sinemurian)
* Suborder Chimaeroidei <small>Patterson 1965</small>
**†''Eomanodon'' <small>Ward and Duffin 1989</small> United Kingdom, Early Jurassic (Pliensbachian)
**Family [[Biology:Callorhinchidae|Callorhinchidae]] <small>Garman, 1901</small>
*** †''[[Biology:Brachymylus|Brachymylus]]'' <small>A. S. Woodward 1894</small> Germany, Early Jurassic (Pliensbachian)
***†''[[Biology:Bathytheristes|Bathytheristes]]'' <small>Duffin 1995</small> Posidonia Shale Formation, Germany, Early Jurassic (Toarcian)
***†''Ottangodus'' <small>Popov, Delsate & Felten, 2019</small> France, Middle Jurassic (Bajocian)
***†''Moskovirhynchus'' Russia, Upper Jurassic
***†''[[Biology:Pachymylus|Pachymylus]]'' United Kingdom, France, Middle Jurassic
**Family †"Edaphodontidae"
***†''[[Biology:Ischyodus|Ischyodus]]'' (40 species) Worldwide, Middle Jurassic–Miocene (also placed in Callorhinchidae)
***†''Elasmodectes'' Europe, Jurassic–Cretaceous
***†''Elasmodus'' Worldwide, Cretaceous–Paleogene
***†''[[Biology:Edaphodon|Edaphodon]]'' Worldwide, Cretaceous–Neogene
***†''[[Biology:Ptyktoptychion|Ptyktoptychion]]'' Australia, Early Cretaceous
***†''Lebediodon'' Europe, Cretaceous
** Family [[Biology:Chimaeridae|Chimaeridae]] <small>Bonaparte, 1831</small>
*** †''Canadodus'' Popov, Johns & Suntok, 2020 Sooke Formation, Canada, [[Earth:Oligocene|Oligocene]]
** Family [[Biology:Rhinochimaeridae|Rhinochimaeridae]] <small>Garman, 1901</small>
*** †''[[Biology:Amylodon|Amylodon]]'' Europe, Late Cretaceous–Oligocene

== See also ==

* List of prehistoric cartilaginous fish
* [[Biology:List of chimaeras|List of chimaeras]]
* [[Biology:Acanthothoraci|Acanthothoraci]]
* [[Biology:Ptyctodontida|Ptyctodontida]]

== References ==

{{Reflist}}


{{Taxonbar|from=Q5290058}}

[[Category:Chimaeriformes| ]]

{{Sourceattribution|Chimaera}}