The above image does not show a specimen of Acanthurus chronixis but a semi adult specimen of Acanthurus pyroferus. Since both species are very closely related, juvenile Acanthurus pyroferus are very often misidentified as Acanthurus chronixis.
The "real" Acanthurus chronixis has been described first by Randall in 1960 from a single adult specimen collected from Kapingamarangi Atoll where it is considered to be endemic. It is known only from the holotype and two possible juveniles and an individual collected in 1980. Kapingamarangi Atoll is an extremely isolated island where no saltwater fish are being caught for the marine ornamental fish trade, so surgeonfish sold under the name of Acanthurus chronixis are, indeed, specimen of Acanthurus pyroferus.