hard corals text index | photo index
Phylum Cnidaria > Class Anthozoa > Subclass Zoantharia/Hexacorallia > Order Scleractinia > Family Merulinidae > Hydnophora sp.
Boulder horn coral
Hydnophora exesa*
Family Merulinidae
updated Oct 2016
Where seen? This boulder-shaped hard coral with conical bumps are sometimes seen on our Southern shores.

Features: Colonies (15-20cm, sometimes much larger), boulder-shaped with irregular lumps and hillocks. The unique feature of the 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. In these boulder-shaped colonies, monticules may be conical short, or long, forming valleys along the surface of the colony. Polyps have short blunt tentacles that surround the base of each monticule. The skeleton is hidden when the tentacles are expanded. Colours seen include brown, green and blue.

Pulau Hantu, Apr 06

Polyp mouths between the monticules.

Tentacles surround the monticules.

Long conical mounds called monticules.

Cyrene Reef, May 08

Monticules may form meandering valleys.

Sisters Island, May 07

Small mouths between monticules.

Pulau Hantu, Feb 10

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

Boulder horn corals on Singapore shores

Photos of Boulder horn corals for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map

Tanah Merah, Jul 09

Photo shared by Loh Kok Sheng on his blog.

Tanah Merah, May 13

Photo shared by Loh Kok Sheng on flickr.

East Coast Park Big Splash, Jun 15

Photo shared by Loh Kok Sheng on facebook.

Labrador, Aug 02

Pulau Hantu
, Jul 12

Photo shared by Loh Kok Sheng on flickr.

South Cyrene, Oct 10

Photo shared by Loh Kok Sheng on flickr.

Terumbu Bemban, Apr 11

Photo shared by Loh Kok Sheng on his blog.

Terumbu Semakau, May 18

Photo shared by Loh Kok Sheng on facebook.

Raffles Lighthouse, Aug 08

Photo shared by Loh Kok Sheng on flickr.


  • Hydnophora exesa on Corals of the World online on the Australian Institute of Marine Science website: Technical fact sheet.
  • Hydnophora exesa on the IUCN Red List of Threatened Species website: Technical fact sheet.
  • Hydnophora on Reef Corals of the Indo-Malayan Seas, the Marine Species Identification Portal: Technical fact sheet.
  • Hydnophora exesa on SeaLife Base: Technical fact sheets.
  • 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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