BULLETIN OF MARINE SCIENCE, 83(2): 391–399, 2008 391 Bulletin of Marine Science © 2008 Rosenstiel School of Marine and Atmospheric Science of the University of Miami NEW TAXA PAPER DESCRIPTION OF THE FIRST ROBOASTRA SPECIES (NUDIBRANCHIA, POLYCERIDAE, NEMBROTHINAE) FROM THE WESTERN ATLANTIC Marta Pola, J. Lucas Cervera, and Terrence M. Gosliner ABSTRACT A new species of polycerid nudibranch of the genus Roboastra (Roboastra ricei sp. nov.) is described from its type locality of Florida; it is also known from North Carolina. he animal is dark yellow with numerous dark blue, almost black, small spots scattered on the notum and both sides of the body. he oral tentacles, the rhinophores, the posterior part of their rhinophore sheaths and the gill branches are dark blue at the tip, light blue in the middle, and yellow at their bases. he edge of the foot is also dark blue. Two other species of the genus, Roboastra europaea García Gómez, 1985, and Roboastra caboverdensis Pola, Cervera and Gosliner, 2003, are known from the Eastern Atlantic Ocean, but have not been found in the Western Atlantic. Roboastra ricei appears as the sister taxa of the two Eastern Atlantic species, although this relationship is not well supported. his description brings the number of species of the genus to seven. he distinctive color pattern, diferences in the radula and reproductive system and its geographical distribution characterize this species and clearly distinguish it from all other described species. Similarly, COI and 16S mitochondrial nucleotide sequences clearly distinguish this species as distinct from all other members of the clade. Based on morphological and molecular phylogenetic analyses, Tambja tentaculata Pola, Cervera and Gosliner, 2005, its within the clade of Roboastra species. In order to maintain the monophyly of Roboastra, we transfer this species to Roboastra. he taxonomy and phylogeny of the genus Roboastra has been reviewed in the last few years (Pola et al., 2003, 2005, 2007). As a result of these studies, two new species were added to this genus, Roboastra caboverdensis Pola, Cervera, and Gosliner, 2003, from the Cape Verde Archipelago and Roboastra leonis Pola, Cervera, and Gosliner, 2005, from the Galápagos Islands, while Roboastra rubropapulosa (Bergh, 1905) was considered as synonym of Roboastra gracilis Bergh (1877) and Roboastra arika Burn, 1967, was considered as nomen dubium (Pola et al., 2005). Features shared by mem- bers of the genus Roboastra (sensu Burn, 1967) are the well-developed oral tentacles as dorso-laterally grooved cylindrical projections, small salivary glands, the presence of elongated pouches at the junction of the oral tube and the buccal bulb, oral tube long and penis with spines arranged in helicoidal rows. Moreover, the preliminary phylogeny based on morphological analysis (Pola et al., 2005) indicated that the ge- nus Roboastra was monophyletic with high bootstrap support, with R. gracilis and Roboastra luteolineata Baba (1936), both from the Indo-Paciic, being the basal spe- cies of this clade. Later, Pola et al. (2007) showed that the recently described species, Tambja tentaculata Pola, Cervera, and Gosliner, 2005, should be included within Roboastra in order to maintain the monophyly of the genus. Here we describe the irst Western Atlantic species of Roboastra. he coloration of this species is unique among the species of the genus, and the presence of dorso-lat- erally grooved oral tentacles together with its internal anatomy permits us to include it within the genus Roboastra.