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. The body is deep and compressed, its depth usually equal to length.

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. 2024, Mola alexandrini in Fishes of Australia, accessed 24 May 2024, 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).  


Body deep, compressed, depth about equal to length. Head profile with bump, chin with bump, both more evident with age; ips not funnel-like, closing in roundish form. Skin with a rough texture, body scales rectangular. 

Pectoral fin small, rounded, not fitting into shallow groove on side of body. Clavus rounded, supported by 14–24 (mode 17) clavus fin-rays, of which 8–15 (12) bear ossicles; ossicles close together, much broader than spaces between them.


Circumglobal in tropical to temperate waters, with Australian records from Coffs Harbour, NSW (30°18'S) to Geographe Bay, WA (33°37'S) including TAS, also Cobourg Peninsula, NT, and Lord Howe Island, absent from the polar regions.


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.


Although ocean sunfish were 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.


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).

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.


The species is named in honour of Antonio Alessandrini, who published an anatomical study of Mola gills in 1839.

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. 2024


Atlas of Living Australia

Bump-head Sunfish, Mola alexandrini (Ranzani 1839)


Allen, G.R., Hoese, D.F., Paxton, J.R., Randall, J.E., et al. 1976. Annotated checklist of the fishes of Lord Howe Island. Records of the Australian Museum 30(15): 365-454 figs 1-2 (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 (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. (as Mola ramsayi)

Britz, R. 2022. Comments on the holotype of Orthragoriscus alexandrini, Ranzani 1839 (Teleostei: Molidae). Zootaxa 5195(4): 391-392. https://doi.org/10.11646/ZOOTAXA.5195.4.6

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 https://doi.org/10.5962/bhl.part.21630 (as Mola ramsayi)

Giglioli, E.H. 1883. Zoology at the Fisheries Exhibition II. Notes on the Vertebrata. Nature (London) 28: 313-316 (described as Mola ramsayi, type locality New South Wales, Australia) See ref at BHL

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. (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. (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. (as Mola ramsayi)

Katayama, E. & Matsuura, K. 2016. Fine structure of scales of ocean sunfishes (Actinopterygii, Tetraodontiformes, Molidae): another morphological character supporting phylogenetic relationships of the molid genera. Bulletin of the National Museum of Nature and Science (Ser. A) 42(2): 95-98.

Larson, H.K., Williams, R.S. & Hammer, M.P. 2013. An annotated checklist of the fishes of the Northern Territory, Australia. Zootaxa 3696(1): 1-293. https://doi.org/10.11646/zootaxa.3696.1.1

Last, P.R., Scott, E.O.G. & Talbot, F.H. 1983. Fishes of Tasmania. Hobart : Tasmanian Fisheries Development Authority 563 pp. figs. (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. https://doi.org/10.1093/zoolinnean/zlx040 (as Mola mola)

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. https://doi.org/10.1111/jfb.12769

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

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

Sawai, E. & Nyegaard, M. 2023. Response to Britz (2022) regarding the validity of the giant sunfish Mola alexandrini (Ranzani, 1834) (Teleostei: Molidae). Zootaxa 5383(4): 561-574. https://doi.org/10.11646/ZOOTAXA.5383.4.7

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. (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 https://doi.org/10.1017/S1755267213000377. (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 (as Mola ramsayi)

Whitley, G.P. 1931. Studies in Ichthyology No. 4. Records of the Australian Museum 18(3): 96-133 figs 1-2 pls 11-16 (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  https://doi.org/10.1007/s10228-008-0089-3 (as Mola sp. group A)

Quick Facts

CAAB Code:37470001

Depth:0-5000 metres

Habitat:Pelagic, mesopelagic, oceanic

Max Size:3.3 metres

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CAAB distribution map