Chaetodon

Chaetodon is a tropical fish genus in the family Chaetodontidae. Like their relatives, they are known as "butterflyfish". This genus is by far the largest among the Chaetodontidae, with about 90 living species included here, though most might warrant recognition as distinct genera.

Taxonomy

Proposed subgenera

Several subgenera have been proposed for splitting out of this group. It is becoming clear how the genus might be split up, with a range of DNA sequence data in large parts agreeing with S.D. Blum's landmark 1988 phylogenetic assessment of osteology.
Basically, a core group around the type species Chaetodon capistratus would remain in Chaetodon, while maybe four clades would be split off. These could use the names Lepidochaetodon, Megaprotodon and Rabdophorus, and there is one unnamed group containing the three-banded butterflyfish and its relatives. But the monophyly of the Lepidochaetodon group is not fully established; it is both unclear whether Rhombochaetodon is a lineage distinct from Exornator, and whether Lepidochaetodon is indeed closer to these than to any other Chaetodon, particularly to some lineages otherwise placed in Megaprotodon.
Prognathodes, for some time contained in Chaetodon, is worthy of recognition as full genus, as is Roa.
Historically, more distantly related fish were placed in Chaetodon too, for resembling them in details – e.g. the common scat Scatophagus argus, which has a similar shape and size, as well as armored larvae like the Chaetodontidae – or simply because they are colorful, smallish, and unusual-looking – e.g. the quite unrelated paradise fish, as C. chinensis.
The classification proposed in Fessler and Westneat is based on the species of Chaetodon they sampled and these sorted into the following clades:

Clade 1	Clade 2	Clade 3	Clade 4
C. robustus C. hoefleri	C. kleini C. unimaculatus C. fremblii C. burgessi C. xanthurus C. paucifasciatus C. mertensi C. quadrimaculatus C. citrinellus C. multicinctus C. punctatofasciatus C. pelewensis C. sedentarius C. dolosus C. miliaris C. guentheri	C. austriacus C. trifasciatus C. ornatissimus C. reticularis C. meyeri C. larvatus C. baronessa C. trifascialis C. rainfordi C. octofasciatus C. bennetti C. plebius C. speculum C. zanzibarensis	C. austriacus C. trifasciatus C. ornatissimus C. reticularis C. meyeri C. larvatus C. baronessa C. trifascialis C. rainfordi C. octofasciatus C. bennetti C. plebius C. speculum C. zanzibarensis

Extant species

There are currently 87 recognized species in this genus:

''Chaetodon sensu stricto''

''C. robustus'' group

''Lepidochaetodon'' group

*Nota bene: including Burgessius, Heterochaetodon and possibly Rhombochaetodon; tentatively placed here.

Species	Common name	Image
Chaetodon daedalma D. S. Jordan & Fowler, 1902	Wrought-iron butterflyfish
Chaetodon interruptus C. G. E. Ahl, 1923	Yellow teardrop butterflyfish
Chaetodon kleinii Bloch, 1790	Sunburst butterflyfish, black-lipped butterflyfish, Klein's butterflyfish
Chaetodon litus J. E. Randall & D. K. Caldwell, 1973	Easter Island butterflyfish
Chaetodon nippon Steindachner & Döderlein, 1883	Japanese butterflyfish
Chaetodon smithi J. E. Randall, 1975	Smith's butterflyfish
Chaetodon trichrous Günther, 1874	Tahiti butterflyfish
Chaetodon unimaculatus Bloch, 1787	Teardrop butterflyfish

*Nota bene: including Tifia. C. daedalma, C. litus, C. nippon, and C. smithi are tentatively placed here.

Species	Common name	Image
Chaetodon argentatus H. M. Smith & Radcliffe, 1911	Asian butterflyfish
Chaetodon blackburnii Desjardins, 1836	Brownburnie
Chaetodon burgessi G. R. Allen & Starck, 1973	Burgess' butterflyfish
Chaetodon declivis J. E. Randall, 1975	Marquesas butterflyfish
Chaetodon flavocoronatus R. F. Myers, 1980	Yellow-crowned butterflyfish
Chaetodon fremblii E. T. Bennett	Blue-striped butterflyfish
Chaetodon madagaskariensis C. G. E. Ahl, 1923	Seychelles butterflyfish
Chaetodon mertensii G. Cuvier, 1831	Atoll butterflyfish
Chaetodon mitratus Günther, 1860	Indian butterflyfish
Chaetodon paucifasciatus C. G. E. Ahl, 1923	Eritrean butterflyfish, crown butterflyfish
Chaetodon tinkeri L. P. Schultz, 1951	Hawaiian butterflyfish
Chaetodon xanthurus Bleeker, 1857	Pearlscale butterflyfish, Philippines chevron butterflyfish, yellow-tailed butterflyfish

Nota bene: including Roaops, might belong in Exornator; tentatively placed here. C. blackburnii, C. declivis, C. flavocoronatus, C. mitratus, and C. tinkeri tentatively placed here.

''Megaprotodon'' group

Nota bene: tentatively placed here.

Species	Common name	Image
Chaetodon austriacus Rüppell, 1836	Blacktail butterflyfish, exquisite butterflyfish
Chaetodon lunulatus Quoy & Gaimard, 1825	Redfin butterflyfish, oval butterflyfish
Chaetodon melapterus Guichenot, 1863	Arabian butterflyfish
Chaetodon trifasciatus M. Park, 1797	Indian redfin butterflyfish, melon butterflyfish

Nota bene: tentatively placed here.

Species	Common name	Image
Chaetodon aureofasciatus W. J. Macleay, 1878	Golden butterflyfish
Chaetodon octofasciatus Bloch, 1787	Eightband butterflyfish
Chaetodon rainfordi McCulloch, 1923	Rainford's butterflyfish
Chaetodon tricinctus Waite, 1901	Three-striped butterflyfish

Nota bene: C. tricinctus tentatively placed here in Discochaetodon.

Species	Common name	Image
Chaetodon baronessa G. Cuvier, 1829	Eastern triangle butterflyfish
Chaetodon larvatus G. Cuvier, 1831	Hooded butterflyfish
Chaetodon triangulum G. Cuvier, 1831	Triangle butterflyfish

Nota bene: tentatively placed here.

Species	Common name	Image
Chaetodon trifascialis Quoy & Gaimard, 1825	Chevron butterflyfish, triangulate butterflyfish, V-lined butterflyfish

Nota bene: C. andamanensis is tentatively placed here in Tetrachaetodon.

''Rabdophorus'' group

Nota bene: Including Aspilurochaetodon and Chaetodontops. C. auripes, C. gardineri, C. leucopleura, C. nigropunctatus, and C. xanthocephalus are tentatively placed in this group.

''Incertae sedis''

Nota bene: most are probably either Chaetodon sensu stricto or C. robustus group.

Fossil species

The following fossil species are known:

Subgenus †Arambourgchaetodon
* †Chaetodon ficheuri Arambourg, 1927
Subgenus †Blumchaetodon
* †Chaetodon wattsi Marramà, Giusberti & Carnevale, 2022

The species Chaetodon penniger Bogachev, 1964 from the late Oligocene of Azerbaijan cannot be confidently assigned to this genus due to the incompleteness of the fossil.

Evolution & fossil record

The earliest confirmed specimens of Chaetodon are from Early Oligocene-aged coral reef deposits of Italy, belonging to the extinct species Chaetodon wattsi. This fossil is roughly concurrent when the family is thought to have radiated into its modern genus diversity. Indeterminate Chaetodon fossil specimens referred to Chaetodon hoefleri are known from the Late Oligocene of Slovenia and the mid-late Miocene of Poland.
As it is not easy to distinguish this genus from close relatives, it may be that some Oligocene fossils are actually of other Chaetodontidae. The fossil record of this family is scant, with only Chelmon being known from Miocene remains. As even crude molecular clocks suggest that the ancestors of the Chaetodon and the Chelmops lineage diverged in the Late Eocene already, nothing more can be said without new fossils being discovered.