Southern Stoplight Loosejaw, Malacosteus australis Kenaley 2007

Other Names: Black Hinged-head, Black Loosejaw, Blunthead Dragonfish

Southern Stoplight Loosejaw, Malacosteus australis. Source: Australian National Fish Collection, CSIRO. License: CC by Attribution-NonCommercial-ShareAlike

A species of barbeled dragonfish found in the deep waters off southern and south-eastern Australia.

Cite this page as:
Bray, D.J. 2022, Malacosteus australis in Fishes of Australia, accessed 10 Dec 2022,

Southern Stoplight Loosejaw, Malacosteus australis Kenaley 2007

More Info


East of Moreton Island, Queensland, to ESE of Bremer Bay, Western Australia. Elsewhere the species occurs in temperate and sub-Antarctic waters of the southern hemisphere, the tropical Indian Ocean, and waters of the Indo-Australian Archipelago.


Dorsal fin 16-21; Anal fin 18-23; Pectoral fin 3-5; Pelvic fin 6; Branchiostegal rays 7-9; Vertebrae 45-51.

Male postorbital photophore 3.7-6.4% upper jaw length, 0.9-1.7% SL; female postorbital photophore 2.5-4.4% upper jaw length, 0.6-1.2% SL; IP photophores 5-7 in 3-7 clusters.


Maximum known length is 16.6 cm for a male and 19.2 cm for a female.


Feeds on mesopelagic fishes and invertebrates, especially copepods. The Southern Loosejaw presumably uses the large accessory orbital photophore (AO) in employing a far-red visual system as part of its foraging strategy (Kenaley 2007).


Red light cannot penetrate into the deep oceanic waters, and as a result, most animals living in the deep-sea have lost the ability to see the colour red. Therefore, the vast majority of bioluminescent animals living in the deep-sea produce a blue light. Not only does Malacosteus have a photophore just behind the eye that produces a blue light, they also have a large elliptical photophore under the eye that produces red bioluminescence. This allows them to shine a red light that cannot be seen by their unsuspecting prey, giving them a huge advantage in their dark environment.


Loosejaws have a flexible connection between the occiput and the first vertebra, allowing them to swallow large prey items by bending their head far back to widen their gape.

Similar Species

Differs mainly from Malacosteus niger in having a smaller postorbital photophore in both sexes, lower numbers of lateral photophores, somewhat smaller jaws and a fleshy orbit.


The specific name australis is from the Latin austral, meaning "southern" in reference to the southern distribution of this species.

Species Citation

Malacosteus australis Kenaley 2007, Copeia 2007(4): 893, Figs. 4-5. Type locality: Tasman Sea, off Brush Island, 35°36'S, 150°55'E, depth 650-2000 m.


Bray, D.J. 2022


Atlas of Living Australia

Southern Stoplight Loosejaw, Malacosteus australis Kenaley 2007


Gomon, M.F., Glover, C.J.M. & Kuiter, R.H. (eds). 1994. The fishes of Australia's south coast. State Print, Adelaide. 992 pp. (as Malacosteus sp.)

Kenaley, C.P. 2007. Revision of the stoplight loosejaw genus Malacosteus (Teleostei: Stomiidae: Malacosteinae), with description of a new species from the temperate Southern Hemisphere and Indian Ocean. Copeia 2007(4): 886-900.[886:ROTSLG]2.0.CO;2

Kenaley, C.P., Harold, A.S. & Gomon, M.F. 2008. Family Stomiidae. pp. 240-254 in Gomon. M.F., Bray, D.J. & Kuiter, R.H (eds). Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp.

Schnell, N.K. & Johnson, G.D. 2017. Evolution of a functional head joint in deep-sea fishes (Stomiidae). PLoS ONE 12(2): e0170224: 1-11.

Williams, A. 2020. Malacosteus australis. The IUCN Red List of Threatened Species 2020: e.T137568083A137570724. Accessed on 20 October 2022.

Quick Facts

CAAB Code:37110001


Conservation:IUCN Least Concern

Depth:500-2000+ m

Habitat:Mesopelagic, bathypelagic

Max Size:19+ cm SL

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