distinguished from other corals by their black, flexible skeletons and near-total lack of any kind of protection from sediment. All black corals have small or medium-sized polyps and a chitin skeleton, lined with small spines. Genera List of genera according to the World Register of Marine Species: Family Antipathidae Ehrenberg, 1834 Allopathes Opresko & , 1994 Antipathes Pallas, 1766 Cirrhipathes de Blainville, 1830 Hillopathes van Pesch, 1914 Pseudocirrhipathes Bo et al., 2009 Pteropathes , 1889 Stichopathes Brook, 1889 Family Aphanipathidae Opresko, 2004 subfamily Acanthopathinae Opresko, 2004 Acanthopathes Opresko, 2004 Distichopathes Opresko, 2004 Elatopathes Opresko, 2004 Rhipidipathes Milne-Edwards & Haime, 1857 subfamily Aphanipathinae Opresko, 2004 Aphanipathes Brook, 1889 Asteriopathes Opresko, 2004 Phanopathes Opresko, 2004 Pteridopathes Opresko, 2004 Tetrapathes Opresko, 2004 Family Cladopathidae Kinoshita, 1910 subfamily Cladopathinae Kinoshita, 1910 Chrysopathes Opresko, 2003 Cladopathes Brook, 1889 Trissopathes Opresko, 2003 subfamily Hexapathinae Opresko, 2003 Heteropathes Opresko, 2011 Hexapathes Kinoshita, 1910 subfamily Sibopathinae Opresko, 2003 Sibopathes Van Pesch, 1914 Family Leiopathidae Haeckel, 1896 Leiopathes Haime, 1849 Family Myriopathidae Opresko, 2001 Antipathella Brook, 1889 Cupressopathes Opresko, 2001 Myriopathes Opresko, 2001 Plumapathes Opresko, 2001 Tanacetipathes Opresko, 2001 Family Schizopathidae Brook, 1889 Abyssopathes Opresko, 2002 Alternatipathes Molodtsova & Opresko, 2017 Bathypathes Brook, 1889 Dendrobathypathes Opresko, 2002 Dendropathes Opresko, 2005 Lillipathes Opresko, 2002 Parantipathes Brook, 1889 Saropathes Opresko, 2002 Schizopathes Brook, 1889 Stauropathes Opresko, 2002 Taxipathes Brook, 1889 Telopathes MacIsaac & Best, 2013 Umbellapathes Opresko, 2005 Family Stylopathidae Opresko, 2006 Stylopathes Opresko, 2006 Triadopathes Opresko, 2006 Tylopathes Brook, 1889 Physical characteristics The skeleton grows of these corals grow in many patterns unique to black corals, such as whips, trees, fans, or coils. These range in size from , though polyps can be as small as in size. Skeletons are also lined with tiny spikes. These spikes are roughly in size, and vary widely in terms of size, length, proportion, and sharpness. A layer of "bark" forms around the skeleton as the coral grows. The polyps that live inside this bark are less than and are gelatinous and have six tentacles (the same as hard corals and unlike soft corals, which have eight). These polyps can be nearly any color. Some corals also have "sweeper tentacles", which can grow up to long. Though individual polyps are either male or female, entire colonies are typically hermaphroditic. Unlike the vast majority of other corals, black corals have no protection against abrasive materials such as sand and rocks and lack muscular development which