The dusky morwong was first formally described in 1850 as Cheilodactylus nigricans by the Scottish naval surgeon, arctic explorer and naturalist Sir John Richardson with the type locality given as King George Sound in Western Australia.

The specific namenigricans means "blackish", as the species description was based on a drawing which showed a dark greyish-black colour on the back, head and fins.

[4] Genetic and morphological analyses strongly suggest that Dactylophora should be placed in the family Latridae, along with almost all of the other species formerly classified in the Cheilodactylidae.

[6] Dusky morwong adults are greyish to brownish grey on the upper body and whitish ventrally.

The juveniles have deeper bodies which are silvery marked with dark bands on the upper flanks extending upwards onto the dorsal fin.