Deep-sea Ophiuroidea (Echinodermata) from the Danish Galathea II Expedition, 1950-52, with taxonomic revisions.
The brittle star samples collected by the Danish cruise 'Galathea II' (1950-52) had not been studied completely. We examined the remaining deep-sea samples (400 m) and present the species inventory, discussing taxonomic issues in relation to recent phylogenetic data. About 235 samples were examined, over 9,300 individuals, from 67 species and 74 sampling localities, at depths of 425-5340 m. The species complex Amphiophiura bullata (Thomson, 1877) is morphologically not well separated, but molecular data suggest at least two clades. We propose to apply A. bullata for Atlantic and Australian populations and A. convexa (Lyman, 1878) for the North Pacific clade. We consider A. bullata pacifica Litvinova, 1971 conspecific with A. convexa. Ophiuroglypha irrorata (Lyman, 1878) and its subspecies are a polyphyletic group with unclear morphological boundaries. We propose to transfer Ophiura ossiculata (Koehler, 1908), Ophiura plana (Lütken Mortensen, 1899) and Ophiura scomba Paterson, 1985 to Ophiuroglypha. Silax Fell, 1962, until now synonymised with Amphioplus Verrill, 1899, is proposed as a valid genus with the species S. verrilli (Lyman, 1879), S. consors (Koehler, 1908), S. daleus (Lyman, 1879), S. patulus (Lyman, 1879) and S. magnificus (Koehler, 1907). Triplodia Turner Hallen, 2011 (a replacement name for Triodia A. M. Clark, 1970, due to homonymy) is synonymised with Silax, and possible specimens of its type species Triodia abdita A. M. Clark, 1970 are analysed. The species limits of Ophiacantha cosmica Lyman, 1879 and Ophiacantha pacifica Lütken Mortensen, 1899 could not be confirmed morphologically, but published molecular data suggest two clades. We propose to apply O. pacifica to the Northern/Central Pacific population and O. cosmica to the Southern Pacific/Antarctic population.