Guyniidae Hickson 1910

Guynia annulata

Stephen D. Cairns
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Classification from Vaughan and Wells (1943) and Wells (1956), as modified and amended by Cairns (1989, 1995) and Stolarski (2000, hypothesis A).

Although Stolarski (2000) placed the Guyniidae as a family incertae sedis within the order Scleractinia (Hypothesis A) or as a separate family within the superfamily Caryophyllioidea (Hypothesis B), we have adopted the more traditional placement of Guyniidae as a family in the superfamily Flabelloidea. We do, however, accept Stolarski's (2000) reassignment of all genera previously placed in Guynidae (except Guynia) to other families. Thus, the genera Truncatoguynia and Stenocyathus are reassigned to the Stenocyathidae Stolarski, 2000 (superfamily Caryophyllioidea) and the genera Schizocyathus, Microsmilia, Pourtalocyathus, and Temnotrochus are reassigned to the Schizocyathidae Stolarski, 2000 (superfamily Volzeioidea). This leaves only one genus and one species, Guynia annulata, in the family Guyniidae.

Containing group: Flabelloidea


Guynia annulata is known from the Pliocene to the Recent, and is widespread in today's oceans in tropical and temperate regions. It occurs in relatively deep water (28-1300 m) and is exclusively azooxanthellate. Although this lack of reliance on symbiosis allows Guynia to live beyond the euphotic zone (layer of light penetration) and at cold temperatures, it limits the animals to relatively small size. Adult Guynia annulata are only 1.0-1.3 mm in calicular diameter, but may be up to 10 mm long.

Guyniids are exclusively solitary in growth form, never forming colonies. They are inconspicuous, cryptic animals, often having elongate, worm-like growth forms. Vermiform coralla are often mistaken for serpulid polychaete worm tubes, but are easily distinguished with a microscope by having septa inside their tubular corallum. Little is known about their ecology and relative abundance in the oceans.


The most characteristic feature of the guyniids are their mural pores/spots, which are small (less than 0.1 mm in diameter) pores, indentations, or spots of differential calcification that occur in rows along the theca in each interseptal space. According to Vaughan and Wells (1943), the pores are formed during periodic rapid pulses of growth, and the more solid theca between the pores are formed during slower growth. Regardless, the pores are subsequently filled with calcium carbonate, but often of a different color (milky white) than the rest of the theca, resulting in conspicuous spots. After the coral dies and the skeleton begins to erode, these in-fillings are the first to decay, resulting in pores once again.

Guyniids also differ from the Flabellidae, the only other family in the superfamily, by having smaller, commonly cylindrical coralla, and, in general, have fewer septa (Cairns, 1989: 40). Other references including information on the guyniids include Duncan (1872), Hickson (1910), Zibrowius (1980), and Stolarski (2000).

Other Names for Guynia annulata


Cairns, S. D. 1979. The deep-water Scleractinia of the Caribbean Sea and adjacent waters. Studies on the fauna of Curaçao and other Caribbean Islands, 57: 341 pp.

Cairns, S. D. 1989. A revision of the ahermatypic Scleractinia of the Philippine Islands and adjacent waters, Part 1: Fungiacyathidae, Micrabaciidae, Turbinoliinae, Guyniidae, and Flabellidae. Smithsonian Contributions to Zoology, 486: 136 pp.

Cairns, S. D. 1995. The marine fauna of New Zealand: Scleractinia (Cnidaria: Anthozoa). New Zealand Oceanographic Institute Memoir, 103: 210 pp.

Cairns, S. D., B. W. Hoeksema, and J. van der Land. 1999. Appendix: List of Extant Stony Corals. Atoll Research Bulletin, 459: 13-46.

Cairns, S. D. and N. B. Keller. 1993. New taxa and distributional records of azooxanthellate Scleractinia from the tropical south-west Indian Ocean. Annals of the South African Museum, 103(5): 213-292.

Duncan, P. M. 1872. On the structure and affinities of Guynia annulata, Dunc., with remarks upon persistence of Palaeozoic types of Madreporaria. Philosophical Transactions of the Royal Society of London, 162(1): 29-40.

Hickson, S. J. 1910. On a new octoradiate coral, Pyrophyllia inflata (new genus and species). Memoirs and Proceedings of the Manchester Literary and Philosophical Society, 54(12): 1-7.

Stolarski, J. 2000. Origin and phylogeny of Guyniidae (Scleractinia) in the light of microstructural data. Lethaia, 33: 13-38.

Vaughan, T. W., and J. W. Wells. 1943. Revision of the suborders, families, and genera of the Scleractinia. Geological Society of America, Special Papers, 44: 363 pp.

Wells, J. W. 1956. Scleractinia. Pp. F328-F444 In: Moore, R. C. (editor) Treatise on Invertebrate Paleontology, Part F: Coelenterata. University of Kansas Press, Lawrence.

Zibrowius, H. 1980. Les Scléractiniares de la Méditeranée et de l'Atlantique nord-oriental. Memoires de l'Institut Océanographique, Monaco, 11: 284 pp.

Title Illustrations
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Scientific Name Guynia annulata
Comments This species is known from the Pliocene to Recent and is one of the smallest known scleractinian corals.
Specimen Condition Fossil -- Period: Late Pliocene of Panama
Body Part showing octameral septal arrangement and some mural pores
View Calicular view
Size calicular diameter of 0.9 mm
Image Use creative commons This media file is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0.
Copyright © 2002
About This Page

Creation of this page was supported by US National Science Foundation grants DEB95-21819 and DEB 99-78106 (in the program PEET - Partnerships to Enhance Expertise in Taxonomy) to Daphne G. Fautin, grant DEB99-78086 (in the program PEET) to Stephen D. Cairns, and grant OCE 00-03970 (in NOPP, the National Oceanographic Partnership Program) to D.G.F. and Robert W. Buddemeier.

Technical assistance was rendered by Adorian Ardelean.

The author welcomes the opportunity to identify specimens from this family, and offers to incorporate them into the collections of the National Museum of Natural History, Smithsonian, unless their return is requested.

Smithsonian Institution, Washington, D. C., USA

Correspondence regarding this page should be directed to Stephen D. Cairns at

Page: Tree of Life Guyniidae Hickson 1910. Guynia annulata. Authored by Stephen D. Cairns. The TEXT of this page is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

Citing this page:

Cairns, Stephen D. 2002. Guyniidae Hickson 1910. Guynia annulata. Version 28 October 2002. in The Tree of Life Web Project,

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