Malacosteus australis, the southern stoplight loosejaw, is a species of barbeled dragonfish.

It also differs in having somewhat smaller jaws, a fleshy orbit, and several subtle morphological traits.

[1] It is known for its red bioluminescence which helps M. australis visualize in the aphotic deep sea.

Malacosteus have a large single tear-dropped size accessory light organ.

[2] In the mesopelagic region, this red light is undetectable visually to all the other fish.