A new species of Eusirus Krøyer, 1845 (Amphipoda, Amphilochidea, Eusiridae) from the seamount of the Caroline Plate, with redescription of Meteusiroides keyensis Pirlot, 1934

A new Eusirus Krøyer, 1845 species within the family Eusiridae Stebbing, 1888 is described based on specimens collected from seamounts of the Caroline Plate. Eusirus carolinussp. nov. is characterized by having large, well-pigmented eyes, the distomiddorsal mediodorsal pointed process only present on pleonites 1 and 2, epimeral plate 3 with a smooth posterior margin, the elongated telson only cleft 20%, and the rami of uropod 3 being equal in length. A rare eusirid species, Meteusiroides keyensis Pirlot, 1934, is redescribed as providing the living coloration based on one female specimen. Sequences of two genes (16S rRNA and COI) were used to analyze their relationships with other species in the family Eusiridae and confirm the taxonomic placement. The result supports the monophyly of Cleonardo Stebbing, 1888; Eusirus and Rhachotropis S.I. Smith, 1883; and is consistent with morphological classification.