Melanonus zugmayeri, the arrowtail, is a species of mesopelagic gadiform belonging to the pelagic cod family Melanonidae.

[3] It has an elongate body, covered in black cycloid scales, which is compressed laterally, reaching its deepest point at the dorsal fin origin before tapering gradually towards the tail.

[2] The teeth in the lower jaw are of uneven size; this trait is used to distinguish the species from its congener M. gracilis, however there is some confusion over whether this distinction is valid.

[5] In addition to these canals there are conspicuous and numerous superficial neuromasts, a trait it shares in common with the melamphaid fish Poromitra capito, consisting of raised papillae in which continuous lines of hair cells are embedded.

It is known to predate on crustaceans, with natant decapods reported from stomach contents alongside euphausiid krill and the amphipod Phronima.