Census of Octocorallia (Cnidaria: Anthozoa) of the Azores (NE Atlantic) with a nomenclature update.

Zoological nomenclature revisions are essential for biodiversity studies and indispensable to avoid naming and description of already described species and should be valued in all subsequent studies considering biology, molecular biology, ecology or habitat mapping of deep-sea species. Herein, a thorough revision of the taxonomic literature on Octocorallia since the beginning of deep-sea exploration in the Azores is provided. Since 1870, when the first octocoral, Virgularia mirabilis (Müller, 1776), was recorded in the Azores a cyclic pattern on the taxonomical study of octocorals reveals the deep-sea investigation efforts made on the region at different periods: Prince Albert I of Monaco, Biaçores and recent expeditions. The first decade of this millennium was the peak on taxonomic research of cold-water octocorals in the Azores with 11 publications targeting gorgonians and soft corals (Alcyonacea) and specific sub-orders within it. Ninety-eight names of Octocorallia were found to be given in the economic exclusive zone of the Azores. While 25 names were changed or added to the known Azorean octocoral diversity, 3 species identified in the region and unreported in the reviewed literature, increase the number to 101 species. Twenty-five names were synonymized while three species names were unmasked as errors in need of taxonomical clarification. This is the highest species richness of Octocorallia found in Europe and in any Northern Atlantic archipelago so far, representing ~60% of the most diverse center of endemism of South Africa, with a part in the Eastern Atlantic. Further research on taxonomy may reveal new species to science.