Acanthurus

Lore & Background

The genus Acanthurus was first proposed as a subgenus of Chaetodon in 1775 by Peter Forsskål, though he recognized it likely differed even at the family level. In 1856, Desmarest designated Teuthis hepatus as the type species, but this is a synonym of Paracanthurus hepatus, which would make Paracanthurus synonymous with Acanthurus. An alternative type species, Harpurus fasciatus (a synonym of Acanthurus triostegus), was proposed in 1788.

In 2014, it was suggested that Chaetodon sohal, described by Forsskål in 1775, should be the type species, as it had been designated by Jordan and Evermann in 1917. The genus Ctenochaetus has been proposed for merging with Acanthurus, as Acanthurus is currently paraphyletic; all Ctenochaetus species nest within Acanthurus, while A. nubilis and A. pyroferus nest within Ctenochaetus. The 5th edition of Fishes of the World recognizes both genera as valid in the tribe Acanthurini.

Evolution

The name Acanthurus derives from Ancient Greek words meaning 'spine' and 'tail', referring to the scalpel-like bony plates on the caudal peduncle, which also inspire the common names surgeonfish and doctorfish. Fossil remains are known from the Middle Miocene of the former Paratethys region, including Austria, Croatia, Hungary, and Ukraine, with specimens from Austria and Ukraine assigned to the extinct species †Acanthurus haueri. These fossils coincide with the Middle Miocene Climatic Optimum and likely inhabited coralgal and bryozoan-dominated reefs. Specimens from Monte Bolca in Italy were previously assigned to Acanthurus but have since been placed in their own genera.

Characteristics

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 can protrude the jaws. The 8 to 28 teeth in the jaws are fixed with flattened, serrated tips. Typically there are 11 spines in the dorsal fin, and a single spine on each side of the caudal peduncle that can be pressed into a groove.