Slender Sunfish, Ranzania laevis (Pennant 1776)

Other Names: Dwarf Sunfish, Oblong Sunfish, Ranzania, Short Sunfish, Slender Mola, Truncated Sunfish, Trunkfish, Tsunami Fish

A Slender Sunfish, Ranzania laevis, washed ashore in Namibia. Source: J Kemper / Fishbase. License: CC by Attribution-NonCommercial


A rare small ocean sunfish with a slender oblong body, a pointed snout with a small oval funnel-like mouth (that is premanently open), long pectoral fins, and ‘smooth’ skin covered in tiny hexagonal scutes. 

Slender Sunfish are dark blue above, brilliant silvery on the sides and below, with variable blue, grey, brown or green stripes and spots, and a series of dark stripes curving below and behind the eye to the underside.

Although rarely seen in coastal waters, large shoals occasionally strand themselves along Australia's south-west coast. Although considered poor swimmers by some, they are actually agile and fast, and sufficiently powerful to breach out of the water (Nyegaard et al. 2017). 

Video of a Slender Sunfish leaping from the water and a school stranding in the Canary Islands.

Video of a large school of juvenile Slender Sunfishin the Canary Islands.

Video of a Slender Sunfish.

See inside Ranzania laevis at the Digital Fish Library with 3D MRI images.

Cite this page as:
Bray, D.J. 2017, Ranzania laevis in Fishes of Australia, accessed 07 Jun 2020,

Slender Sunfish, Ranzania laevis (Pennant 1776)

More Info


Found worldwide in most tropical and temperate seas, usually well offshore. Slender Sunfish are fast swimmers, and often travel in large schools. Although rarely seen in coastal waters, large shoals occasionally strand themselves along the south-west Australian coast.


Dorsal-fin rays 16-20; Anal-fin rays 18-19; Pectoral-fin rays 13; Clavus 21 ossicles.

Body depth 49-54% SL; head length about 39% SL. Body relatively slender, more or less oblong in shape,; lips funnel-like, closing as a vertical slit; skin smooth with small hexagonal scutes; pectoral fin elongate.


The smallest ocean sunfish, reaching a length of only 100 cm TL.


Dark blue above, brilliant silver on sides and below, with some variably blue, grey, brown or green darkish stripes and spots; series of dark stripes curving below and behind eye to ventral surface.


Feeds on zooplankton, especially small crustaceans, and on small fishes and squids.


The species appears to form large spawning aggregations (Horn et al. 2016). 



  • IUCN Red List : Near Threatened


Slender Sunfish occasionally strand in their hundreds along Australia's southwest coast. The species prefers warm waters, and schools may be transported south in the tropical  Leeuwin Current, before being carried inshore by upwellings and eddies. 

Similar Species

Bass, Anna & Dewar, Heidi & Thys, Tierney & Todd. Streelman, J & A. Karl, Stephen. (2005). Evolutionary divergence among lineages of the ocean sunfish family, Molidae (Tetraodontiformes). Marine Biology. 148. 405-414. 10.1007/s00227-005-0089-z. 


Species Citation

Ostracion laevis Pennant 1776. British Zoology 3: 129, pl. 19. Type locality: Cornwall, England.


Bray, D.J. 2017


Australian Faunal Directory

Slender Sunfish, Ranzania laevis (Pennant 1776)


  • Bass, A.L., Dewar, H., Thys, T., Streelman, J.T. & Stephen, A.K. 2005. Evolutionary divergence among lineages of the ocean sunfish family, Molidae (Tetraodontiformes). Marine Biology 148: 405-414.
  • Bray, D.J. 2008. Family Molidae, in Gomon. M.F., Bray, D.J. & Kuiter, R.H (eds) Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp.
  • Britz, R. & Johnson, G.D. 2005. Occipito-vertebral fusion in ocean sunfishes (Teleostei: Tetraodontiformes: Molidae) and its phylogenetic implications. Journal of Morphology 266: 74–79.
  • 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
  • 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.
  • Horn, T.S., Machado, R., Weiss, C. V.C., Giora, J. & Malabarba, L.R. 2016, Analysis of an astounding aggregation of Ranzania laevis (Molidae: Actinopterygii) in the tropical south-western Atlantic. Journal of Fish Biology 89: 2212–2218. doi:10.1111/jfb.13119 Abstract
  • Hureau, J.-C. & Monod, T. (eds) 1973. Checklist of the Fishes of the North-Eastern Atlantic and of the Mediterranean (CLOFNAM). Paris : UNESCO Vol. 1 683 pp.
  • 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.
  • Hutchins, J.B. & Thompson, M. 1983. The Marine and Estuarine Fishes of South-western Australia. Perth : Western Australian Museum 103 pp. 345 figs.
  • Johnson, G.D. & Britz, R. 2005. Leis' Conundrum: Homology of the Clavus of the Ocean Sunfishes. 2. Ontogeny of the Median Fins and Axial Skeleton of Ranzania laevis (Teleostei, Tetraodontiformes, Molidae). Journal of Morphology 266(1): 11-21.
  • Konstantinidis, P. & Johnson, G.D. 2012. Ontogeny of the jaw apparatus and suspensorium of the Tetraodontiformes. Acta Zoologica 93: 351-366. 10.1111/j.1463-6395.2011.00509.x.  
  • Leis JM. 1977. Development of the eggs and larvae of the slender mola, Ranzania laevis. Bulletin of Marine Science 27: 448-466. PDF available Open access
  • Leis JM. 1984. Tetraodontoidei: development, pp 447– 450. In: Moser HG, Richards WJ, Cohen DM, Fahay MP, Kendall AW, Richardson SL, editors. Ontogeny and systematics of fishes. Lawrence, KS: Allen Press.
  • Liu, J., Zapfe, G., Shao, K.-T., Leis, J.L., Matsuura, K., Hardy, G., Liu, M., Tyler, J. & Robertson, R. 2015. Ranzania laevis. (errata version published in 2016) The IUCN Red List of Threatened Species 2015: e.T193615A97668925. Downloaded on 11 May 2017.
  • Nyegaard, M., Loneragan, N. & Santos, M.B. 2017. Squid Predation by Slender Sunfish Ranzania laevis (Molidae). Journal of Fish Biology doi:10.1111/jfb.13315 Abstract
  • Pennant, T. 1776. British Zoology. London : Chester Vol. 3 425 pp. 73 pls.
  • Pollard, J. (ed.) 1980. G.P. Whitley's Handbook of Australian Fishes. North Sydney : Jack Pollard Publishing Pty Ltd 629 pp.
  • Raven, H.C. 1939. Notes on the anatomy of Ranzania truncata, a plectognath fish. Am Mus Novitates 1038: 1-7.
  • Robison, B.A. 1975. Observations on living juvenile specimens of the Slender Mola, Ranzania laevis (Pisces, Molidae). Pacific Science 29(1): 27-29. PDF
  • Santini, F. & Tyler, J.C. 2002. Phylogeny of the ocean sunfishes (Molidae, Tetraodontiformes), a highly derived group of teleost fishes. Ital J Zool 69: 37-43.
  • Schmidt, J. 1921. Contributions to the knowledge of the young of the sun-fishes (Mola and Ranzania). Medd Comm Hav 6: 1-13.
  • 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.
  • Sherman, K. 1961. Occurrence of early developmental stages of the oblong ocean sunfish Ranzania laevis (Pennant) in the central North Pacific. Copeia 1961 (4): 467-470.
  • Shimose, T., Yokawa, K. & Tachihara, K. 2013. Occurrence of slender mola Ranzania laevis (Pennant, 1776) in stomachs of blue marlin Makaira nigricans Lacepede, 1802. Journal of Applied Ichthyology 29: 1160–1162. 10.1111/jai.12206. 
  • Smith, K.A., Hammond, M, & Close, P.G. 2010. Aggregation and stranding of elongate sunfish (Ranzania laevis) (Pisces: Molidae) (Pennant, 1776) on the southern coast of Western Australia. Journal of the Royal Society of Western Australia 93: 181-188. 10.1093/acprof:oso/9780199583652.003.0012. 
  • Wan, R.-J. & Zhang, R.Z. 2005. Spatial distribution and morphological characters of the eggs and larvae of the slender mola Ranzania laevis from the tropical waters of the western Pacific Ocean. Acta Zoologica Sinica 51(6): 1034-1043 (in Chinese)
  • Swainston, R. 2011. Swainston's Fishes of Australia: The complete illustrated guide. Camberwell, Victoria : Penguin Australia 836 pp. 
  • Whitley, G.P. 1933. Studies in Ichthyology No. 7. Records of the Australian Museum 19(1): 60-112 figs 1-4 pls 11-15 
  • Whitley, G.P. 1933. Sunfishes. Victorian Naturalist 49: 207-213.
  • Whitley, G.P. 1937. Further ichthyological miscellanea. Memoirs of the Queensland Museum 11(2): 113-148 figs 11-13
  • Yamanoue, Y., Miya, M., Matsuura, K., Katoh, M., Sakai, H. & Nishida, M. 2004. Mitochondrial genomes and phylogeny of the ocean sunfishes (Tetraodontiformes: Molidae). Ichthyological Research 51: 269–273. 10.1007/s10228-004-0218-6. 

Quick Facts

CAAB Code:37470004

Conservation:IUCN Least Concern

Depth:0-300 m

Habitat:Oceanic, epipelagic

Max Size:100 cm TL

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CAAB distribution map