The monotypic Gymnoamblyopus is known only from a single specimen collected in Fly River, Papua New Guinea. It differs from all other amblyopine gobies by the following combination of characters: only one anal-fin pterygiophore anterior to first hemal spine; no spatulate second anal-fin pterygiophore; no chin barbels; no scales; no raised dermal folds or ridges; pleural ribs short and posteriorly directed; and mouth vertical.