The new genus Aglaona: the first abyssal aglajid (Heterobranchia: Cephalaspidea: Aglajidae) with a description of two new species from the north-western Pacific Ocean

Abstract In this paper we describe the new genus Aglaona, the first abyssal genus of the family Aglajidae, comprising two new species: Aglaona rudmani sp. nov. from the Sea of Okhotsk (inhabiting a depth of 3206 m) and Aglaona valdesi sp. nov. from the Pacific slope of the Kuril Islands (at a depth of 3374–3580 m). For species descriptions and inference of relationships, we have followed an integrative approach, including molecular phylogenetic analyses based on four markers (COI, 16S, H3 and 28S) and a morphological analysis based on traditional anatomical dissections and scanning electron microscopy. The new genus is characterized by a well-developed radula with marginal teeth (2:1:0:1:2) and an internal bulloid shell with a wing-like parietal callus. External and internal morphology of Aglaonagen. nov. species is similar to that of the philinoid genus Laona (family Laonidae). Phylogenetic analyses support the inclusion of the new genus in the family Aglajidae, but its sister-relationships are unresolved. Our results suggest that Aglaonagen. nov. possesses several plesiomorphic characters, and that the reduction of shell and radula in Aglajidae occurred in parallel in different lineages.