hard corals text index | photo index
Phylum Cnidaria > Class Anthozoa > Subclass Zoantharia/Hexacorallia > Order Scleractinia > Family Merulinidae > Hydnophora sp.
Branching horn coral
Hydnophora rigida*
Family Merulinidae
updated Nov 2019
Where seen? This hard coral with conical bumps and forming branching colonies is sometimes seen on some of our undisturbed Southern islands.

Features: Colonies (15-20cm) bushy. An open tangle of thick, short cylindrical branches, often arising from an encrusting base. The unique feature of these Hydnophora corals are the small conical mounds (0.5cm or smaller), called monticules (also hydnae or hydnophores), that form where the corallite walls of adjacent polyps fuse together. Polyps have short blunt tentacles that surround the base of each monticule. The tentacles that are usually extended only at night. Colours seen include blue and brown.

Raffles Lighthouse, Jun 07

Conical mounds called monticules

Monticules often fused into ridges
forming short valleys.

Tentacles around the mounds.

*Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.

Branching horn corals on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Tanah Merah Ferry Terminal, Jun 22

Photo shared by Loh Kok Sheng on facebook

Tanah Merah Ferry Terminal, Jun 22

Photo shared by Kelvin Yong on facebook

Tanah Merah, Jun 10

Photo shared by Loh Kok Sheng on flickr.

Sentosa Serapong, May 12

Photo shared by Loh Kok Sheng on flickr.

Sisters Island, Jul 04

Pulau Semakau, Sep 23

Photo shared by Richard Kuah on facebook.

Terumbu Semakau, May 13

Photo shared by Loh Kok Sheng on flickr.

Terumbu Semakau, May 18

Photo shared by Loh Kok Sheng on facebook.

Raffles Lighthouse, Jul 06


  • Danwei Huang, Karenne P. P. Tun, L. M Chou and Peter A. Todd. 30 Dec 2009. An inventory of zooxanthellate sclerectinian corals in Singapore including 33 new records (pdf). Raffles Bulletin of Zoology Supplement No. 22: 69-80.
  • Veron, Jen. 2000. Corals of the World Australian Institute of Marine Science, Australia. 3 volumes.
  • Chou, L. M., 1998. A Guide to the Coral Reef Life of Singapore. Singapore Science Centre. 128 pages.
  • Erhardt, Harry and Daniel Knop. 2005. Corals: Indo-Pacific Field Guide IKAN-Unterwasserachiv, Frankfurt. 305 pp.
  • Borneman, Eric H. 2001. Aquarium Corals: Selection, Husbandry and Natural History T.F. H Publications. 464 pp
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