Acanthurus

Acanthurus was first proposed as a subgenus of Chaetodon in 1775 by the Swedish-speaking Finnish explorer, orientalist and naturalist Peter Forsskål, although he recognised that it was probably different from Chaetodon even at the family level. In 1856 Desmarest designated Teuthis hepatus, which had been described from a type now known to have been collected at Ambon Island in the Moluccas (other erroneous type localities were named) in 1758 by Linnaeus, as the type species of the genus.^[1][2] T. hepatus is a synonym of Paracanthurus hepatus and this would make Paracanthurus synonymous with Acanthurus. An alternative would be to use the name Harpurus proposed as a monospecific genus in 1788 by Johann Reinhold Forster when he described Harpurus fasciatus, a synonym of Acanthurus triostegus. It has been proposed that the International Commission on Zoological Nomenclature should be petitioned to stabilise the genera Acanthurus and Paracanthurus.^[3] In 2014 it was proposed that the type species of Acanthurus should be Chaetodon sohal, which had also been described by Forsskål in 1775 as a member of the subgenus alongside C. bifasciatus, C. nigrofuscus and C. unicornis, and had been designated as the type species by Jordan and Evermann in 1917.^[4]

It has been proposed that the genus Ctenochaetus should be merged with Acanthurus, as Acanthurus is currently paraphyletic.^[5][6] All Ctenochaetus species are nested within Acanthurus, while A. nubilis and A. pyroferus are furthermore nested within Ctenochaetus.^[6] The 5th edition of Fishes of the World recognises these two genera as valid and classifies them as the two genera in the tribe Acanthurini of the subfamily Acanthurinae within the family Acanthuridae.^[7]

The genus name Acanthurus comes from Ancient Greek ἄκανθα (ákantha), meaning "spine", and οὐρά (ourá), meaning "tail", a reference to the scalpel-like bony plates on the caudal peduncle, these also give rise to the vernacular English names surgeonfish and doctorfish.^[8]

Fossil remains of Acanthurus are known from the Middle Miocene of the former Paratethys region, including Austria, Croatia, Hungary, and Ukraine. The specimens from Austria and Ukraine are assigned to the extinct species †Acanthurus haueri. Their presence coincides with the Middle Miocene Climatic Optimum, and they likely inhabited coralgal and bryozoan-dominated reefs.^[9][10] Previously, specimens from Monte Bolca in Italy were also assigned to the modern Acanthurus,^[11] but they have since been split into their own genera.^[12]

Acanthrus surgeonfishes are distributed around the world in tropical waters.^[13]

There are currently 41 recognized species in this genus:^[14]

Species	Common name	Image
Acanthurus achilles G. Shaw, 1803	Achilles surgeonfish
Acanthurus albimento K. E. Carpenter, J. T. Williams & M. D. Santos, 2017	White-chin surgeonfish[15]
Acanthurus albipectoralis G. R. Allen & Ayling, 1987	White-fin surgeonfish
Acanthurus auranticavus J. E. Randall, 1956	Orange-socket surgeonfish
Acanthurus bahianus Castelnau, 1855	Barber surgeonfish
Acanthurus bariene Lesson, 1831	Black-spot surgeonfish
Acanthurus blochii Valenciennes, 1835	Ring-tail surgeonfish
Acanthurus chirurgus (Bloch, 1787)	Doctorfish tang
Acanthurus chronixis J. E. Randall, 1960	Chronixis surgeonfish
Acanthurus coeruleus Bloch & J. G. Schneider, 1801	Atlantic blue tang
Acanthurus dussumieri Valenciennes, 1835	Eye-stripe surgeonfish
Acanthurus fowleri de Beaufort, 1951	Fowler's surgeonfish
Acanthurus gahhm (Forsskål, 1775)	Black surgeonfish
Acanthurus grammoptilus J. Richardson, 1843	Fine-lined surgeonfish
Acanthurus guttatus J. R. Forster, 1801	White-spotted surgeonfish
Acanthurus japonicus (P. J. Schmidt, 1931)	Japan surgeonfish
Acanthurus leucocheilus Herre, 1927	Pale-lipped surgeonfish
Acanthurus leucopareius (O. P. Jenkins, 1903)	White-bar surgeonfish
Acanthurus leucosternon E. T. Bennett, 1833	Powder-blue surgeonfish
Acanthurus lineatus (Linnaeus, 1758)	Lined surgeonfish
Acanthurus maculiceps (C. G. E. Ahl, 1923)	White-freckled surgeonfish
Acanthurus mata (G. Cuvier, 1829)	Elongate surgeonfish
Acanthurus monroviae Steindachner, 1876	Monrovia surgeonfish
Acanthurus nigricans (Linnaeus, 1758)	White-cheek surgeonfish
Acanthurus nigricauda Duncker & Mohr (de), 1929	Epaulette surgeonfish
Acanthurus nigrofuscus (Forsskål, 1775)	Brown surgeonfish
Acanthurus nigroris Valenciennes, 1835	Blue-lined surgeonfish
Acanthurus nigros Günther, 1861	Grey-head surgeonfish[16]
Acanthurus nubilus (Fowler & B. A. Bean, 1929)	Pin-striped surgeonfish
Acanthurus olivaceus Bloch & J. G. Schneider, 1801	Orange-spot surgeonfish
Acanthurus polyzona (Bleeker, 1868)	Black-barred surgeonfish
Acanthurus pyroferus Kittlitz, 1834	Chocolate surgeonfish
Acanthurus randalli J. C. Briggs & D. K. Caldwell, 1957
Acanthurus reversus J. E. Randall & Earle, 1999
Acanthurus sohal (Forsskål, 1775)	Sohal surgeonfish
Acanthurus tennentii Günther, 1861	Double-band surgeonfish
Acanthurus thompsoni (Fowler, 1923)	Thompson's surgeonfish
Acanthurus tractus F. Poey, 1860	Ocean surgeonfish[17]
Acanthurus triostegus (Linnaeus, 1758)	Convict surgeonfish
Acanthurus tristis J. E. Randall, 1993	Indian Ocean mimic surgeonfish
Acanthurus xanthopterus Valenciennes, 1835	Yellow-fin surgeonfish

• †Acanthurus haueri (von Meyer, 1842) (Middle Miocene of Austria and Ukraine)^[9]

A. xanthopterus tail spine and teeth

Acanthurus surgeonfishes have disc shaped, highly laterally compressed bodies with a steep dorsal profile to the head. They have a small mouth positioned low on the head and the fish can protrude the jaws. The 8 to 28 teeth in the jaws are fixed and have flattened, serrated tips. There are typically 11 spines in the dorsal fin. There is a single spine on each side of the caudal peduncle and these can be pressed down into a groove.^[13]

The Indo-Pacific yellowfin surgeonfish (A. xanthopterus) is the largest species with a maximum published total length of 70 cm (28 in) while the smallest is the black-barred surgeonfish (A. polyzona) with a maximum published total length of 11 cm (4.3 in).^[14]