Hammerjaw, Omosudis lowii Günther 1887

Other Names: Omosudid

The Hammerjaw, Omosudis lowii, collected on the 2003 NORFANZ Expedition to the seamounts of the Tasman Sea. Source: Mark McGrouther / NORFANZ Founding Partners . License: All rights reserved

A voracious predator with a deep lower jaw and a huge mouth full of long sabre-like teeth - some in the jaws, and others in the roof of the mouth. Scales are absent and the Hammerjaw has a distinctive iridescent silvery-bronze colour.

Cite this page as:
Dianne J Bray, Omosudis lowii in Fishes of Australia, accessed 21 Mar 2018, http://fishesofaustralia.net.au/home/species/4020

Hammerjaw, Omosudis lowii Günther 1887

More Info


Found worldwide in tropical and temperate oceans; meso- and bathypelagic at 730–4000 m.


Meristic features: Dorsal-fin rays 9–11; Anal-fin rays 13–14; Caudal-fin rays 19; Pectoral-fin rays 12–13; Pelvic-fin rays 8; Lateral line absent.

Head large, blunt, length 27–33% SL, front of lower jaw deep; mouth large; teeth present in jaws, palatines and pharyngeals; jaw teeth in a single row, lower jaw with huge, prominent slender canines, one of which is enlarged; upper jaw with small canines along edge, and several pairs of large, slender canines on palatines.

Dorsal fin short-based, centred on back; sides of body with a lateral dermal keel on the caudal peduncle above the posterior half of the anal fin.


To about 30 cm.


Iridescent, brassy-silvery, shading to black or dark brown on the back, with minute to small, brown or black spots densely scattered over the body; black stripe covering keel midlaterally on caudal peduncle; tips of snout and lower jaw and forward edges of jaw dark brown to black; dorsal, anal and caudal fins dusky to black; other fins mostly lacking pigment.


Hammerjaws are voracious mid-water predators, feeding mostly on squid and other fishes, often taking prey items larger than themselves.


Hammerjaws are synchronous hermaphrodites, having both male and female reproductive tissue at the same time. Fertilization is external, eggs and larvae are unknown. 


Of no interest to fisheries.


IUCN Red List: Not evaluated.

EPBC Act 1999: Not listed


Hammerjaws are relatively rare fishes, possibly becasue they are strong swimmers and may evade capture in trawl nets. Large adult specimens are extremely rare.

Similar Species

The Hammerjaw is the only species in the genus Omosudis.

Species Citation

Omosudis lowii Günther 1887 Rept. Sci. Res. Voy. Challenger 22(57): 201, fig. 6, pl. 52(c, c'), Philippine Seas and Magdalena, Madeira.


Dianne J Bray

Hammerjaw, Omosudis lowii Günther 1887


Bray, D.J. 2008. Family Alepisauridae – Lancetfishes, hammerjaws. In: Gomon, M.F., D.J. Bray & R.H. Kuiter. Fishes of Australia’s Southern Coast. Reed New Holland, Chatswood, Australia.

Ege, V. 1958. Omosudis Günther, bathypelagic genus of fish. 'Dana' Reports 47: 1-19, figs 1-3.

Günther, A. 1887. Report on the deep-sea fishes collected by H. M. S. Challenger during the years 1873-76. Report on the Scientific Results of the Voyage of H. M. S. Challenger 22(57): i-lxv + 1-268, Pls. 1-66.

Maul, G.E. 1986 Omosudidae. p. 280. In Smith, M.M. & P.C. Heemstra (eds.) Smiths' sea fishes.

Nielsen, J.G. & A. Jespersen. 1986. Morphometric changes in ripening Omosudis lowei (Pisces, Omosudidae). Archiv für Fischereiwissenschaft 37: 59-67.

Paxton, J.R., D.F. Hoese & J.E. Gates. 2006. Alepidauridae (pp. 497-498). In: Beesley, P.L. & A. Wells. Zoological Catalogue of Australia. Volume 35. Fishes. Parts 1-3.

Paxton, J.R. & V.H. Niem. 1999. Omosudidae. In Carpenter, K.E. & V.H. Niem (eds). FAO Species Identification Guide for Fishery Purposes. The Living Marine Resources of the Western Central Pacific. Volume 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophrynidae). FAO, Rome. Pp. iii-vi, 1398-2068

Rofen, R.R. 1966. Family Omosudidae. In Olsen, Y.H. (ed.) Fishes of the western North Atlantic. Memoir. Sears Foundation of Marine Research 1(5): 462-481 figs 163-172.

Quick Facts

CAAB Code:37127001

Biology:Synchronous hermaphrodites

Depth:730-4000 m


Habitat:Mesopelagic, bathypelagic

Max Size:30 cm

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