Hexacorallia

Part of speech: noun

Definitions

1. A subclass of marine cnidarians comprising stony corals and sea anemones, whose polyp tentacles and internal parts typically occur in multiples of six
2. A group of anthozoan animals, including reef-building stony corals and anemones, characterized by sixfold body symmetry and numerous tentacles
3. The taxonomic subclass of sea anemones and hard corals, distinguished by a body plan with six-part radial symmetry and tentacles arranged in sixes

Etymology: Hexacorallia is a scientific coinage, not an ancient word, and its history is the story of a classification changing. The name was created in the 19th century from Greek "hex" (six) and "korallion" (coral), referring to the six-fold symmetry of the group's polyps, whose tentacles and internal partitions come in multiples of six. It names one of the two major subclasses of stony and sea anemone-like cnidarians, the other being Octocorallia, whose members have eight tentacles. The word is a taxonomic label rather than a term with a long vernacular life. Its ending "-ia" follows the Latin-style pattern used for class and subclass names in zoology, and the same pattern produced the names of countless other groups. The Greek roots themselves are old, but nobody in antiquity used them in this combination; the Greek "korallion" was an ordinary word for coral, and the six-fold idea only became meaningful once biologists studied the anatomy of these animals closely.