New Holocene calcified tubular foraminifera in acervulinid macroids from the Kikai Jima shelf, Ryukyu Islands, southwestern Japan

Two new genera and species of tubular foraminifera (Shimenawa okuyamae gen. et sp. nov. and Yorishiro morii gen. et sp. nov.) are described from approximately 4000-year-old nuclei of deep-water acervulinid macroids collected from the shelf off Kikai Jima, Ryukyu Islands (Japan). Macroids form extensive beds on mobile sandy and gravelly bioclastic carbonate sediments at water depths of 75–97 m. SEM and Raman analyses show that Shimenawa okuyamae is characterized by a porcelaneous texture with randomly oriented, needle-shaped calcite crystals, whereas Yorishiro morii possesses a three-layered test composed of rhombohedral, plate-shaped, and rod-shaped calcite crystals. These shell textures have not previously been recognized or described in detail in foraminifera. Shimenawa okuyamae is tentatively assigned to the Squamulinacea based on its porcelaneous, imperforate, unilocular shell. Due to its novel shell texture among tubular foraminifera, Yorishiro morii cannot be assigned with certainty to any family or higher taxonomic rank.