Distichopora robusta sp. nov., the first shallow-water stylasterid (Gnidaria: Hydrozoa: Stylasteridae) fi:-om the tropical eastern Pacific

Stylasterid corals comprise about 250 species, making them the second largest group of calcified cnidarians, only the Scleractinia having more species (i.e. 1500; Cairns, 1999; Cairns et al., 1999). They are distributed worldwide in both deep and shallow-water marine environments, but most species occur in water depths of 200-500m (Cairns, 1984, 1992). Among the tropical shallow-water species, currently assigned to either Stylaster or Distichopora, most form branching, fan-like colonies 5 to 25 cm tall and are remarkable for their bright colours, including violet, red, yellow and orange. These shallow-water species are abundant mostly in the Indo-West Pacific, with only two species•Stylaster blatteus (Boschma, 1961) and Stylaster rosaceus (Green) 1886)•occurring in the eastern Atlantic and a single species•Stylaster roseas (Pallas, 1766)•found in the western Atlantic. The first descriptions of shallow-water stylasterids were those of the western Atlantic Stylaster roseas and the IndoPacific Distichopora violácea (Pallas, 1766). Subsequently, about a dozen additional shallow-water species of Distichopora were described for the Indo-West Pacific. This number was greatly reduced by Boschma (1959), who recognized only four valid shallow, Indo-Pacific species of Distichopora (plus two doubtful species). The most widespread of these is D. violácea, ranging from the Red Sea, Seychelles, East Africa, through the Indian Ocean to the central Pacific. Thus far, only for the eastern Pacific have tropical shallow-water stylasterid corals not been described. Here, we describe Distichopora robusta sp. nov., the first tropical shallow-water stylasterid coral from the eastern Pacific. Collected ofT the coast of Panama, this new species has robust branches and lacks well-developed pore rows, the latter feature traditionally considered as the most important diagnostic characteristic oí Distichopora (Cairns, 1983). Colonies of Distichopora robusta sp. nov. were collected at depths of 5 to 25 m on the south side of Isla Jicarita, Gulf of Chiriqui, western coast of Panama. Colonies were preserved in 95% ethanol or kept dried, and were studied using methodology as described by Cairns (1983). The abbreviations used are: MZUSP (Museu de Zoología da Universidade de Sao Paulo, Sao Paulo, Brazil); RMNH (Naturalis, Nationaal Natuurhistorisch Museum, Leiden, the Netherlands); USNM (National Museum of Natural History, Smithsonian Institution, Washington, DC, USA).