Wednesday, September 20, 2017


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Hydnophora (Merulinidae)

Welcome to the Hydnophora genus landing page. In this section, you will find general information about this genus and tips on how to identify it. If you are looking to confirm an observation made with the Coral Finder about a branching Hydnophora, use the image browser below to verify what you saw underwater. Then click on the following link for further comparison with a similar genus: Montipora.

Vital Statistics

  • 6 species
  • Coral Finder p. 5, 16
  • COTW – Vol 2 p. 364-373


Widespread in the Indo-Pacific.

ID Tips

Hydnophora forms branching, thick encrusting or massive colonies.  Although colonies may be found in a range of environments, they predominantly grow in shallow and protected reef areas.

The small corallites are difficult to distinguish underwater as where the walls of neighbouring corallites meet, they fuse forming conical bumps called ‘monticules’ (or hydnophores).  These bumps have ridges running from the apex, down towards the corallites, producing a structure that resembles a lemon squeezer.  Some species may extend their tentacles during the day, masking the surface of the colony and the monticules.

The fused skeletal structures are typical of the Merulinidae family.

(slide show with photos of monticules with tentacles in and out)

Similar Genera

The Coral Finder lists Hydnophora in two key groups with Montipora being a possible candidate for confusion.

Similar genera to branching forms of Hydnophora (Coral Finder p5)

Branching forms of Hydnophora can be confused with Montipora but are easily separated by the coarse monticules typical of Hydnophora. The skeletal structures and bumps of Montipora are much finer.

Branching Hydnophora

Similar genus: Montipora


Taxonomic Changes

Learning Resources

Coral Hub

  • Merulinidae family page


Suggested Reading – Identification Tools

  • Chevalier, J. P. (1975). Les scleractiniaires de la Melanesie Francaise.  II Expedition Francaise sur les recifs coralliens de la Nouvelle-Caledonie. Paris: Singer-Polignac.
  • Davie, P. J., & Phillips, J. A. (2009). 13th International Marine Biological Workshop, The Marine Fauna and Flora of Moreton Bay, Queensland. Memoirs of the Queensland Museum, 54(2), 1-118.
  • Veron, J. E. N. (1985). Corals of Australia and the Indo-Pacific. Sydney: Angus and Robertson.
  • Veron, J. E. N. (2000). Corals of the World. Melbourne: Australian Institute of Marine Science.
  • Veron, J. E. N., & Pichon, M. (1980). Scleractinia of Eastern Australia.  Part 3, Families Agaraciidae, Siderastreidae, Fungiidae, Oculinidae, Merulinidae, Mussidae, Pectiniidae, Carophylliidae, Dendrophylliidae. Australian Institute of Marine Science Monograph Series, IV, 471.
  • Veron, J. E. N., Pichon, M., & Wijsman-Best, M. (1977). Scleractinia of Eastern Australia.  Part 2, Families Faviidae, Trachyphyllidae. Australian Institute of Marine Science Monograph Series, III, 233.
  • Wijsman-Best, M. (1976). Biological results of the Snellius Expedition.  XXVII Faviidae collected by the Snellius Expedition.  II The genera Favites, Goniastrea, Platygyra, Oulophyllia, Leptoria, Hydnophora, and Caulastrea. Zoologische Mededelingen, 50, 45-63.

Suggested Reading – Other Topics