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

• We constructed the most comprehensive, time-calibrated molecular phylogeny to date.
• The tree includes 76% of spe cies and nine loci.
• We find monophyly of Acanthuridae, Acanthurinae, and Nasinae.
• Surgeonfishes originate in the Early Eocene and radiate in the Miocene.
• We suggest dissolving Ctenochaetus into Acanthurus.

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 Early Miocene (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 thick-walled, gizzard-like stomachs evolved only once within Acanthurus and that this morphology has a common origin in Acanthurus and Ctenochaetus. Based on our molecular analyses, in conjunction with the large body of morphological evidence, we recommend dissolving the genus Ctenochaetus into the genus Acanthurus.

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