; phylum Cnidaria, class Anthozoa)
An order of colonial, branching corals in which the polyps are small, with few tentacles (six simple, or eight branched) and few unpaired mesenteries (6, 10, or 12). The skeleton is a branched, thorny, chitinous (see chitin), axial structure, developed from the ectoderm, extending throughout the colony, and surrounded by a fleshy coenosarc containing the polyps. Black corals are non-reef dwellers in depths of 2000–35 000 m. About 20 extant genera are known, one of which is also known from the Miocene.
Subjects: Zoology and Animal Sciences.