Antipatharians, also known as black corals or thorn corals, are an order of soft deep-water corals. These corals can be recognized by their jet-black or dark brown chitin skeletons, surrounded by the polyps (part of coral that is alive). Antipatharians are a cosmopolitan order, existing at nearly every location and depth, with the sole exception of brackish waters. However, they are most frequently found on continental slopes under deep. A black coral reproduces both sexually and asexually throughout its lifetime. Many black corals provide housing, shelter, food, and protection for other animals. Black corals were originally classified in the subclass Ceriantipatharia along with ceriantharians (tube-dwelling anemones), but were later reclassified under Hexacorallia. Though they have historically been used by Pacific Islanders for medical treatment and in rituals, its only modern use is making jewelry. Black corals have been declining in numbers and are expected to continue declining due to the effects of poaching, ocean acidification and climate change. Etymology Despite its name, a black coral is rarely black, and depending on the species can be white, red, green, yellow, or brown. The corals get their name from their black skeletons, which are composed of protein and chitin. Black corals have several different names. One of the more common names is thorn coral, so called because of the microscopic spines all along the skeleton. The name Antipatharia comes from the Ancient Greek word ("against disease"). In the Hawaiian language, a black coral is called ("hard bush growing in the sea"); it is the official state gem of Hawaii. In Malay, the corals are called ("root of the sea"), likely named for their tendency to grow at low-light depths. Taxonomy and classification Black corals have historically been difficult to classify due to poor-quality specimens. They have few distinguishing morphological characteristics, and the few that there are vary across species, similar to other corals. When black corals were first documented by Henri Milne-Edwards and Jules Haime, two French zoologists in 1857, all species of Antipatharia were placed in the family Antipathidae. From 2001 to 2006, marine biologists Dennis Opresko and Tina Molodtsova helped transform the taxonomic system into what it is today. A 2007 phylogenetic study confirmed the new taxonomic system. Blacks corals are classified in the order Antipatharia with 7 families, 44 genera, and 280 distinct species. The families are Antipathidae, Aphanipathidae, Cladopathidae, Leiopathidae, Myriopathidae, Schizopathidae, and Stylopathidae. Black corals can be