The St. Paul’s fingerfin was first formally described as Chaetodon monodactylus in 1819 by the Scottish Army surgeon and botanist Dugald Carmichael with the type locality given as Tristan da Cunha. The specific name monodactylus means “one fingered”, a reference to the elongated 6th lowest fin ray in the pectoral fin. Genetic and morphological analyses strongly support the placement of Nemadactylus in the family Latridae, alongside almost all of the other species formerly classified in the Cheilodactylidae.
