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]