Flatface Seahorse, Hippocampus planifrons Peters 1877

Other Names: Flat-face Seahorse, Low-crowned Sea-horse

A Flatface Seahorse, Hippocampus planifrons, amongst floating algae at Cape Preston, Western Australia, 16 May 2016. Source: Tony Ayling. License: All rights reserved


Cite this page as:
Bray, D.J. 2018, Hippocampus planifrons in Fishes of Australia, accessed 29 May 2020,

Flatface Seahorse, Hippocampus planifrons Peters 1877

More Info


Endemic to tropical Western Australia, from Broome to Dirk Hartog Island. Inhabits algal and rubble reefs in shallow bays from the intertidal to depths of 20 m.


Dorsal fin 23-24 (usually 23); Anal fin 4; Pectoral fin 18-19; trunk rings 11; tail rings 37-38; subdorsal rings 3-4 + 1.

Head relatively small, snout short, about equal to postorbital length; nasal profile convex, rising upwards to angle of about 45° from snout; trunk slender, more than twice as long as its depth in adults.

Spines and tubercles: Body ridges with small tubercles becoming smooth with age. Subdorsal spines 4/0,0,1,1 or 5/0,0,0,1,1; small outwards curving spine above eye; nape spine small, directed anterodorsally; shoulder ring spines small, uppermost spine low and directed outward next to gill-opening, central spine at level just below level of centre of pectoral-fin base, lowermost spine directed outward; small lateral head spine; small spine behind eye; body spines of small to moderate size along dorsal and lateral ridges, few enlarged, most prominently along dorsal-fin base.

Coronet: Coronet slightly raised, 2 small anterior spines, 3 posterior spines of moderate size, central spine enlarged and recurved.
Lateral line: Lateral line pores small, distinct, situated just above lateral ridge at each ring on trunk, reaching about 18th tail ring.

Fins: Dorsal-fin origin variable in position, ranging from before, in front of, on, or behind 8th trunk ring.


Height to 70 mm, but may grow to 120 mm.


In life - females overall greenish brown with dark blotching over dorsal region of trunk and tail; snout with dark lateral spots. In preservative - body mainly brown, snout with dark spots.


Like most other seahorses, this species presumably feeds by sucking small crustaceans and other small prey items, including planktonic zooplankton, into its mouth.


The female uses an ovipositor to transfer her eggs into an elaborate enclosed pouch under the abdomen of the male. The male not only fertilizes the eggs inside the pouch and provides physical protection for the developing embryos, he also osmoregulates and aerates the embryos and may provide some nourishment until the offfspring are born.


Of no interest to fisheries, and not traded in the Asian Traditional Medicine market.


Listed under Appendix II of the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES). As a result, the species is subject to the Convention, http://www.cites.org/.
Listed as Vulnerable (VU A4cd) on the IUCN Red List of Threatened species.
Marine Listed under the Federal Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act 1999). http://www.environment.gov.au/epbc/species/marine.html


H. planifrons has been regarded by some authors as a synonym of H. trimaculatus. Specimens from the Northern Territory and Queensland which were previously misidentified as H. planifrons are the Lowcrown Seahorse, H. dahli.

Some authors regard H. biocellatus to be a junior synonym of H. planifrons.

Similar Species


The specific name planifrons is from the Latin plan meaning flat or level, and frons meaning brow, forehead or forepart, in reference to the flat face of this species.

Species Citation

Hippocampus planifrons Peters 1877, Mber. K. Preuss. Akad. Wiss. Berl. 1876: 851 Type locality: "Naturalists Channel", nw. Australia, 10 fathoms.


Bray, D.J. 2018


Australian Faunal Directory

Flatface Seahorse, Hippocampus planifrons Peters 1877


Kuiter, R.H. 2000. Seahorses, Pipefishes and their Relatives. TMC Publishing, Chorleywood, UK, 240 pp.

Kuiter, R.H. 2001. Revision of the Australian Seahorse of the genus Hippocampus (Syngnathiformes: Syngnathidae) with descriptions of nine new species. Records of the Australian Museum 53: 293-340. PDF Open access

Lourie, S.A., A.C.J. Vincent & H.J. Hall. 1999. Seahorses: an identification guide to the world's species and their conservation. Project Seahorse. London, UK.

Peters, W. 1877. Übersicht der während der von 1874 bis 1876 unter der Commando des Hrn. Capitän z. S. Freiherrn von Schleinitz ausgeführten Reise S. M. S. Gazelle gesammelten und von der Kaiserlichen Admiralität der Königlichen Akademie der Wissenschaften übersandten Fische. Monatsb. Akad. Wiss. Berlin 1876: 831-854.

Pogonoski, J.J., D.A. Pollard & J.R. Paxton. 2002. Conservation Overview and Action Plan for Australian Threatened and Potentially Threatened Marine and Estuarine Fishes, Canberra, Environment Australia, 375 pp.

Pollom, R. 2017. Hippocampus planifrons. The IUCN Red List of Threatened Species 2017: e.T68527310A47728827. http://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T68527310A47728827.en. Downloaded on 21 June 2018.

Whitley, G.P. 1952. Some noteworthy fishes from eastern Australia. Proc. Roy. Soc. N. S. W. 1950/51: 27-32.

Quick Facts

CAAB Code:37282078

Conservation:IUCN Least Concern

Depth:0-20 m

Habitat:Reef associated, algae/rubble areas

Max Size:Height 12 cm


Species Image Gallery

Species Maps

CAAB distribution map