Grammatonotus laysanus was first formally described in 1905 by the American ichthyologist Charles Henry Gilbert with its type locality given as off Laysan in the Northwestern Hawaiian Islands,[1] When Gilbert described this species he classified it in a new monospecific genus, Grammatonotus, and designating G. laysanus as the type species of the genus.

[2] The 5th edition of Fishes of the World classifies Grammatonotus as one of two genera in the family Callanthiidae, which it places in the order Spariformes.

The caudal fin is rounded with two filamentous extensions running from the upper and lower margins.

[4] This species has a maximum published standard length of 12.8 cm (5.0 in).

[4] This is a pelagic and Oceanic species found at depths between 170 and 372 m (558 and 1,220 ft).