Cibicidoides sp. A

Hanagata, S & Nobuhara, T, 2015, Illustrated guide to Pliocene foraminifera from Miyakojima, Ryukyu Island Arc, with comments on biostratigraph, Palaeontologia Electronica (Cambridge, England) 33 (8), pp. 1-142 : 100

Cibicidoides sp. A

Figures 30.5, 30.6

Description. Test very small for the genus, approximately 0.12—0.15 mm in diameter; trochospiral, biconvex but umbilical side more convex; periphery rounded; seven to eight chambers in the last whorl; sutures on dorsal side strongly curving backwards, umbilical side radiate; aperture interiomarginal extending to edge of periphery of last chamber; test thin and finely perforate.

Remarks. We could not find any taxon to assign this specimen to. This form might be a juvenile of any species of Cibicidoides , although all our specimens show the similar small test size and we regard them as adult.

Occurrence. Thirty-nine specimens from only a single sample of the Yonahama Formation.

Figures

FIGURE 30. Family Parrelloididae, Pseudoparrellidae, Discorbinellidae, and Planulinidae. All scale bars = 0.1mm. 1—4. Cibicidoides pachyderma (Rzehak), 1: MPC-26203 from sample MK01 (Yonahama Formation, PL2); 2: MPC- 26204 from sample 4-2 (Minebari F., PL5); 3: MPC-26205 from sample 3-2-up-sand (Onogoshi F., PL1); 4: MPC- 26206 from sample 5-2 (Minebari F., PL5); 3 and 4, inflate-chamber variation. 5, 6. Cibicidoides sp.A, 5: MPC-26207, 6: MPC-26208, both from sample MK01 (Yonahama F., PL2). 7, 8. Parrelloides bradyi (Trauth), 7: MPC-26409 from sample 7 (Yonahama F., PL4); 8: MPC-26410 from sample MK01 (Yonahama F., PL2). 9, 10. Alabaminoides exiguus (Brady), 9: MPC-26108 from sample MK01 (Yonahama F., PL2); 10: MPC-26109 from sample MK02A (Minebari F., PL5). 11, 12. Eilohedra rotunda (Husezima and Maruhasi), 11: MPC-26230 from sample 1-2 (Minebari F., PL5); 12: MPC-26231 from sample MK02B (Minebari F., PL5). 13, 14. Facetocochlea pulchra (Cushman), 13: MPC-26255 from sample 3-2-low-silt (Onogoshi F., PL1); 14: MPC-26256 from sample 5-2 (Minebari F., PL5). 15. Discorbinella montereyensis Cushman and Martin, MPC-26223 from sample 12 (Minebari F., PL5). 16, 17. Laticarinina pauperata (Parker and Jones), 16: MPC-26348 from sample 7 (Yonahama F., PL4); 17: MPC-26349 from sample MK01 (Yonahama F., PL2). 18—21. Hyalinea balthica (Schröter), 18: MPC-26328 from sample MK01 (Yonahama F., PL2); 19: MPC-26329 from sample MK02B (Minebari F., PL5); 20: MPC-26330 from sample 5 (Minebari F., PL5); 21: MPC- 26331 from sample 5-2 (Minebari F., PL5); 20 and 21, inflated-chamber variation.