Corallimorpharia is an order of marine cnidarians closely related to stony or reef building corals (Scleractinia). They occur in both temperate and tropical climates, although they are mostly tropical. Temperate forms tend to be very robust, with wide and long columns, whereas tropical forms tend to have very short columns with a wide oral disc and very short tentacles. The tentacles are usually arranged in rows radiating from the mouth. Many species occur together in large groups, although there are recorded instances of individuals. In many respects, they resemble the stony corals, except for the absence of a stony skeleton. Morphological and molecular evidence suggests that they are very closely related to stony corals. Corallimorpharians occur in a wide range of marine habitats, and can be associated with phase shifts in coral reef ecosystems that result in a change from a hard-coral dominated reef to a soft-coral dominated one. They have been observed to overgrow reefs in a carpet formation. Many species are also common invertebrates kept in marine aquaria. Taxonomy According to World Register of Marine Species, this order contains 46 species within 11 genera: Family Corallimorphidae Hertwig, 1882 Genus Corallimorphus Moseley, 1877 -- 6 species Genus Corynactis Allman, 1846 -- 14 species Genus Paracorynactis Ocaña, den Hartog, Brito & Bos, 2010 -- 1 species Family Discosomidae Verrill, 1869 Genus Amplexidiscus Dunn & Hamner, 1980 -- 1 species Genus Discosoma Rüppell & Leuckart, 1828 -- 11 species Genus Metarhodactis Carlgren, 1943 -- 1 species Genus Platyzoanthus Saville-Kent, 1893 -- 1 species Genus Rhodactis Milne Edwards & Haime, 1851 -- 7 species Family Ricordeidae Watzl, 1922 Genus Ricordea Duchassaing de Fonbressin & Michelotti, 1860 -- 2 species Family Sideractinidae Danielssen, 1890 Genus Nectactis Gravier, 1918 -- 1 species Genus Sideractis Danielssen, 1890 -- 1 species References UFL Zoology - Cnidaria External links Hexacorallia Cnidarian orders