Bump-head Sunfish, Mola alexandrini (Ranzani 1839)

Other Names: Ramsay's Ocean Sunfish, Ramsay's Sunfish, Short Ocean Sunfish, Short Sunfish, Southern Ocean Sunfish, Southern Sunfish

A Bump-head Sunfish, Mola alexandrini, from off New South Wales. Source: Rob Harcourt. License: All rights reserved


A grey to dark reddish-brown ocean sunfish, becoming dusky white below, with grey to dark reddish-brown fins, and many small to larger pale spots and irregular blotches on the body.

The Bump-head Sunfish (also called the Short Sunfish) was previously known as Mola ramsayi (a junior synonym). In Bali, Indonesia, Bump-head Sunfish often gather at cleaning stations to have parasites removed by Schooling Bannerfish.

Video of a Bump-head Sunfish (as Mola ramsayi).

Mola alexandrini being cleaned by Schooling Bannerfish at Nusa Penida, Bali, Indonesia.

A juvenile Short Sunfish, Mola alexandrini, swimming near the surface at Manly, Sydney, November 2016.

Mola alexandrini and Schooling Bannerfish around Nusa Lembongan/Penida, Bali, Indonesia.

Mola alexandrini in Crystal Bay, Nusa Penida, Bali, Indonesia.

Cite this page as:
Bray, D.J. 2020, Mola alexandrini in Fishes of Australia, accessed 09 Dec 2023, https://fishesofaustralia.net.au/home/species/784

Bump-head Sunfish, Mola alexandrini (Ranzani 1839)

More Info


In Australian waters, known from northern New South Wales, around the south to about Geographe Bay, Western Australia, including around Tasmania, off the Cobourg Peninsula, Northern Territory, and in the Lord Howe Island region.

Elsewhere this oceanic inhabitant is widespread in the world’s oceans, preferring warmer waters (absent from Polar regions).  


Head profile with bump; chin with bump; body scales rectangular; clavus rounded, supported by 14–24 (mode 17) clavus fin rays and 8–15 (12) ossicles on the rear margin.

Ocean sunfishes lack a true tail or caudal fin. Instead, they has a clavus, a rudder-like structure formed from extensions of the dorsal and anal fin rays. The clavus is broadly rounded and often has a low scalloped margin of rounded projections (called ossicles).


Grey to dark reddish-brown dorsally, becoming dusky white below, with grey to dark reddish-brown fins, and many small to larger pale spots and irregular blotches on the body.


Once thought to be relatively inactive fishes that fed on pelagic gelatinous animals, recent research and sightings indicate that molas undertake deep-water forays to feed on colonial animals such as siphonophores.


Little is known of the biology of the Bump-head Sunfish.


Similar Species

Mola alexandrini can be distinguished from other species of Mola by the following combination of characters in adults: head profile with bump; chin with bump; body scales rectangular; clavus rounded, supported by 14–24 (mode 17) clavus fin rays and 8–15 (12) ossicles on the rear margin.

Species Citation

Orthragoriscus alexandrini Ranzani 1839, Novi Commentarii Academiae Scientiarum Instituti Bononiensis 3: 75, 78-79, table, Pl. 6 (left). Type locality: Adriatic Sea (Mediterranean Sea)


Bray, D.J. 2020


Atlas of Living Australia

Bump-head Sunfish, Mola alexandrini (Ranzani 1839)


Allen, G.R., Hoese, D.F., Paxton, J.R., Randall, J.E., Russell, B.C., Starck, W.A., Talbot, F.H. & Whitley, G.P. 1976. Annotated checklist of the fishes of Lord Howe Island. Records of the Australian Museum 30(15): 365-454 figs 1-2 (in part as Mola ramsayi)

Bass A.L., Dewar H., Thys T.M., Streelman J.T. & Karl S.A. 2005. Evolutionary divergence among lineages of ocean sunfish family, Molidae (Tetraodontiformes). Marine Biology 148: 405–414 (in part as Mola ramsayi)

Bray, D.J. 2008. Family Molidae. pp. 858-861 in Gomon. M.F., Bray, D.J. & Kuiter, R.H (eds). Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp. (in part as Mola ramsayi)

Fraser-Brunner, A. 1951. The ocean sunfishes (family Molidae). Bulletin of the British Museum (Natural History) Historical Series 1(6): 89-121 figs 1-18 (in part as Mola ramsayi)

Giglioli, E.H. 1883. Zoology at the Fisheries Exhibition II. Notes on the Vertebrata. Nature (London) 28: 313-316

Glover, C.J.M. 1994. Family Molidae. pp. 915-920, figs 808-810, in Gomon, M.F., Glover, C.J.M. & Kuiter, R.H. (eds). The Fishes of Australia's South Coast. Adelaide : State Printer 992 pp. 810 figs. (in part as Mola ramsayi)

Hutchins, J.B. 2001. Molidae. pp. 3966-3968 in Carpenter, K.E. & Niem, T.H. (eds). The Living Marine Resources of the Western Central Pacific. FAO Species Identification Guide for Fisheries Purposes. Rome : FAO Vol. 6 pp. 3381-4218. (in part as Mola ramsayi)

Hutchins, J.B. & Thompson, M. 1983. The Marine and Estuarine Fishes of South-western Australia. Perth : Western Australian Museum 103 pp. 345 figs. (in part as Mola ramsayi)

Last, P.R., Scott, E.O.G. & Talbot, F.H. 1983. Fishes of Tasmania. Hobart : Tasmanian Fisheries Development Authority 563 pp. figs. (in part as Mola ramsayi)

Nyegaard, M. & Sawai, E. 2018. Species identification of sunfish specimens (Genera Mola and Masturus, Family Molidae) from Australian and New Zealand natural history museum collections and other local sources. Data in Brief 19: 2404-2415 https://doi.org/10.1016/j.dib.2018.07.015

Nyegaard, M., Sawai, E., Gemmell, N., Gillum, J., Loneragan, N.R., Yamanoue, Y., Stewart, A.L. 2017. Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition. Zoological Journal of the Linnean Society zlx040. doi: 10.1093/zoolinnean/zlx040 (in part as Mola ramsayi)

Phillips, N.D., Harrod, C., Gates, A.R., Thys, T.M. & Houghton, J.D.R. 2015. Seeking the sun in deep, dark places: mesopelagic sightings of ocean sunfishes (Molidae). Journal of Fish Biology 87: 1118–1126. doi: 10.1111/jfb.12769 Abstract

Ranzani, C. 1839. Dispositio familiae Molarum in genera et in species. Novi Commentarii Academiae Scientiarum Instituti Bononiensis 3: 63-82, Pl. 6 + foldout table. See ref at BHL

Sawai, E., Yamanoue, Y., Nyegaard, M. & Sakai, Y. 2017. Redescription of the bump‑head sunfish Mola alexandrini (Ranzani 1839), senior synonym of Mola ramsayi (Giglioli 1883), with designation of a neotype for Mola mola (Linnaeus 1758) (Tetraodontiformes: Molidae). Ichthyological Research 65: 142–160. https://doi.org/10.1007/s10228-017-0603-6

Scott, T.D., Glover, C.J.M. & Southcott, R.V. 1974. The Marine and Freshwater Fishes of South Australia. Adelaide : Government Printer 392 pp. figs. (in part as Mola ramsayi)

Thys, T.M., Whitney, J., Hearn, A., Weng, K.C., Peñaherrera, C., Jawad, L., Alfaro-Shigueto, J., Mangel, J.C. & Karl, S.A. 2013. First record of the southern ocean sunfish, Mola ramsayi, in the Galápagos Marine Reserve. Marine Biodiversity Records 6: e70 doi:10.1017/S1755267213000377. (in part as Mola ramsayi)

Waite, E.R. 1921. Illustrated catalogue of the fishes of South Australia. Records of the South Australian Museum (Adelaide) 2(1): 1-208 293 figs pl. 1 (in part as Mola ramsayi)

Whitley, G.P. 1933. Sunfishes. Victorian Naturalist 49: 207-213 (in part as Mola ramsayi)

Yoshita, Y., Yamanoue, Y., Sagara, K., Nishibori, M., Kuniyoshi, H., Umino, T., Sakai, Y., Hashimoto, H. & Gushima, K. 2009. Phylogenetic relationships of two Mola sunfishes (Tetraodontiformes: Molidae) occurring around the coasts of Japan, with notes on their geographical distribution and morphological characteristics. Ichthyological Research 56: 232–244 (as Mola sp. A)

Quick Facts

CAAB Code:37470001

Depth:0-5000 metres

Habitat:Pelagic, mesopelagic, oceanic

Max Size:3.3 metres

Species Image Gallery

Species Maps

CAAB distribution map