Alternate Title

The Gulf Surgeon, Acanthurus randalli, a Junior Synonym of the Ocean Surgeon, Acanthurus bahianus (Teleostei: Acanthuridae)


We compared 62 specimens, 48-126.5 mm standard length, of Acanthurus bahianus from the northeastern Gulf of Mexico with 95 specimens from other localities to determine if the distinguishing characters in the original description of the Gulf of Mexico endemic surgeonfish Acanthurus randalli were valid. No color pattern or meristic differences were found, and the only measurement that allowed distinction (91% percent concordance) was the shallower caudal concavity of northeastern Gulf of Mexico specimens. Acanthurus chirurgus from the northeastern Gulf of Mexico also have shallower caudal concavities (93.7% percent concordance) than do conspecifics from other areas, suggesting that this trend may be correlated with some unknown environmental influence. Considering the extended planktonic larval dispersal capabilities of Atlantic surgeonfishes, and that the single divergent morphological character state is also exhibited in a sympatric northeastern Gulf of Mexico population of A. chirurgus, recognition of A. randalli is untenable, and the name is considered a junior synonym of A. bahianus. An identification key to western Atlantic species of Acanthurus that incorporates the results of this study is given.