Bony-Eared Assfish, Acanthonus armatus Günther 1878

A still-frame image of a Bony-Eared Assfish, Acanthonus armatus, from a video filmed by an ROV in the Marianas. Source: NOAA Okeanos Explorer’s 2016 Deepwater Exploration of the Marianas. License: CC by Attribution-NonCommercial-ShareAlike

A brownish to blackish cusk eel with a large head and tapering flabby body, small eyes, a prominent forward-projecting divided spine on the snout, a very long slender spine on the operculum extending well beyond head, and well-developed spines on the lower angle of preoperculum.

Video of Acanthonus armatus in the Western Indian Ocean, depth 2590 m.

Cite this page as:
Bray, D.J. 2022, Acanthonus armatus in Fishes of Australia, accessed 22 Feb 2024,

Bony-Eared Assfish, Acanthonus armatus Günther 1878

More Info


Coral Sea off Cape York, to off southern Queensland, depth range 1768-3246 m. Elsewhere the species occurs worldwide in tropical and subtropical seas, inhabiting bathyal and abyssal depths at 1500-4400 m.


Gill rakers (developed) 16-22; Precaudal vertebrae 9-10.
Head large, body tapering; eye small; snout with prominent, bifid spine; opercular spine long, slender extending well beyond rear margin of head; spines at lower angle of preopercle well-developed.


The Bony-Eared Assfish has heavy sacular otoliths and very large semicircular canals, along with relevant large areas of the brainstem and cerebellum. This suggests that the lateral line and vestibular senses are particularly acute, and the heavy otoliths may indicate that the species is sensitive to low-frequency sound.


The specific name is from the Latin armatus (= armed, armed with a weapon) in reference to the strong spines on the head.

Species Citation

Acanthonus armatus Günther 1878, Ann. Mag. Nat. Hist. (Ser. 5) 2 (nos 7/8/9)(art. 2/22/28): 23. Type locality: North of New Guinea, Challenger station 218, depth 1075 fathoms.


Bray, D.J. 2022


Atlas of Living Australia

Bony-Eared Assfish, Acanthonus armatus Günther 1878


Cohen, D.M. & Nielsen, J.G. 1978. Guide to the identification of genera of the fish order Ophidiiformes with a tentative classification of the order. National Marine Fisheries Service (U.S.). Technical Report 417: 1-72 figs 1-103

Fine, M.L., Horn, M.H. & Cox, B. 1987. Acanthonus armatus, a deep-sea teleost fish with a minute brain and large ears. Proceedings of the Royal Society B: Biological Sciences 230(1259): 257-265.

Golovan, G. & Pahkorukov, N. 1979. A catch of Acanthonus armatus (Family Brotulidae) off the coast of north-west Africa. Journal of Ichthyology 19(2): 142-143.

Günther, A. 1878. Preliminary notices of deep-sea fishes collected during the voyage of H.M.S. Challenger. Annals and Magazine of Natural History 5 2(2, 22, 28): 17-28, 179-187, 248-251 See ref at BHL

Günther, A. 1887. Report on the deep-sea fishes collected by H.M.S Challenger during the years 1873–1876. Report on the Scientific Results of the Voyage of H.M.S. Challenger 1873–1876, Zoology 22(57): 1-268 figs 1-7 pls 1-66 See ref at BHL

Haedrich, R.L. & Merrett, N.R. 1988. Summary atlas of deep-living demersal fishes in the North Atlantic Basin. Journal of Natural History 22: 1325-1362.

Knudsen, S. 2015. Acanthonus armatus. The IUCN Red List of Threatened Species 2015: e.T190201A60796787. Downloaded on 05 July 2017.

Mincarone, M.M., Nielsen, J.G. & Costa, P.A.S. 2008. Deep-sea ophidiiform fishes collected on the Brazilian continental slope, between 11° and 23°S. Zootaxa 1770: 41-64.

Nielsen, J.G. 1997. Deepwater ophidiiform fishes from off New Caledonia with six new species. No. 4. In: Séret, B. (ed.) Résultats des Campagnes MUSORSTOM 17. Mem. Mus. Natl. Hist. Nat. 174: 51-82.

Yeh, H.-M., Lee, M.-Y. & Shao, K.-T. 2005. Fifteen Taiwanese new records of Ophidiid fishes (Pisces: Ophidiidae) collected from the deep waters by the RV Ocean Researcher I. Journal of the Fisheries Society of Taiwan 32(3): 279-299.

Quick Facts

CAAB Code:37228127

Conservation:IUCN Least Concern

Depth:1500-4400 m


Max Size:37.5 cm TL

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