| Summary: | Seamounts are important deep ocean entities that serve as reservoirs for varied types of habitats and fauna. During the Chinese cruises in the northwestern Pacific seamount areas, a new starfish species of order Brisingida, Astrolirus patricki, was found at 1,458–2,125 m depth. All specimens of the new species were observed in situ attaching on hexactinellid sponges, suggesting a possible close relationship between the two taxa. A. patricki sp. nov. is the second known species of the genus, characterized by the abutting plates in the intercostal integument, separated first pair of adambulacral plates and densely distributed proximal spines. Phylogenetic analyses were conducted for order Brisingida to incorporate the new species as well as Hymenodiscus cf. fragilis (Fisher, 1906), Freyella cf. attenuata Sladen, 1889 and two Brisinga spp., for which we present the molecular data for the first time. Phylogenetic trees suggest a close relationship between A. patricki sp. nov. with Brisinga species rather than with Hymenodiscus species, which is inconsistent with morphological taxonomy. This study highlights the distinct morphological and ecological characters of the new species and provides new data for future investigation on Brisingida phylogeny.
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