Review of the abysso-hadal genus Bayerius (Gastropoda: Neogastropoda: Buccinidae) from the North-West Pacific, with description of two new species

The abyssal and hadal Buccinoidea from the north-western Pacific formerly attributed to the genera Tacita and Calliloncha were analyzed for the first time using both multilocus molecular and morphological data. The results allow re-evaluation of the inter- and intrageneric variability of morphological characters and demonstrate that Tacita, Calliloncha and Paracalliloncha are synonyms of Bayerius, a genus widely distributed in the Pacific Ocean. In our reconstructed phylogeny the genus forms a maximally supported clade with Pararetifusus tenuis and Turrisipho dalli. At present, Bayerius includes 10 species, two of which are described herein as new to science, B. inflatus sp. nov. and B. nekrasovorum sp. nov. with one additional undescribed species represented in our material by a single specimen. The genus is reviewed, with the addition of new data on anatomy and distribution, based on newly obtained material. B. peruvianus is synonymized with B. zenkewitchi. Calliloncha nankaiensis together with Costaria crosnieri are attributed to a new genus, Warenius gen. nov., which clusters with several genera of Buccinoidea from biogenic substrata.