A multi-locus timetree of surgeonfishes (Acanthuridae, Percomorpha), with revised family taxonomy

We present the most comprehensive time-calibrated, species-level hypothesis of the timing of Acanthuridae (surgeonfishes and allies) evolution based on 76% of the extant diversity and nine genes. We recover two major acanthurid clades, Nasinae and Acanthurinae, and infer a much more recent Nasinae crown age (17 Ma) compared to a previous dating study for Naso. The Acanthurinae represent an older group that originated ~ 42 Ma, with most diversification occurring since the Late Oligocene (beginning ~ 21 Ma). Our results strongly support a paraphyletic Acanthurus and Ctenochaetus, with multiple analyses recovering a clade grouping Ctenochaetus, A. nubilus and A. pyroferus. Contrary to previous studies, we also provide strong evidence that the thick-walled, gizzard-like stomach morphology evolved only once within the Acanthurus + Ctenochaetus clade. Based on our molecular analyses, in conjunction with the large body of morphological evidence, we recommend dissolving the genus Ctenochaetus into the genus Acanthurus.