CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia (Turborotalia) rikuchuensis Takayanagi & Oda, in Takayanagi et al. 1976
This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.
Citation: Globorotalia (Turborotalia) rikuchuensis Takayanagi & Oda, in Takayanagi et al. 1976Taxonomic rank: speciesType specimens: Holotype (IGPS 75024); paratype (IGPS 75025)Type sample (& lithostrat): Shimokurosawa FormationType age (chronostrat): Middle MioceneType locality: Southern bank of the lwai River. 200 m. downstream from the junction of the lwai and Kubo rivers. Kamikurosawa, lchinoseki City, lwate Prefecture:Type repository: Sendai, Japan; Tohoku University Institute of Geology and Paleontology
Current identification:
Original Description Test moderate in size. low trochospiral. biconvex, nearly flat to slightly convex on spiral side. convex on umbilical side; equatorial periphery slightly lobulate in outline. without carina or pseudocarina; axial periphery rounded; chambers in spiral aspect semicircular, increasing gradually in size; 13 to 14 chambers arranged in about two and a half whorls, usually four and a half to five chambers in the last whorl; sutures rather distinct slightly depressed on both sides, tangential and slightly curved on spiral side. gently curved on umbilical side; umbilicus narrow, deep; wall calcareous. finely perforate. surface finely pitted; aperture interiomarginal, umbilical-extraumbilical. a comparatively high arch, giving a comma-shaped appearance in side view. with a lip. Size: Maximum diameter of holotype (plate 1. figure 4a-4d) 0.29 mm., height 0.19 mm. Maximum diameter of paratype (plate 1. figure 5a-5c) 0.21 mm., height 0.14 mm. Unfigured paratypes range from 0.20 mm. to 0.30 mm. in diameter. Etymology: This species is named after Rikuchu, an old provincial name for the southern part of lwate Prefecture Extra details from original publication Remarks: This species resembles Globorotalia (Turborotalia) adamantea Saito from the Middle Miocene of Japan in general appearance, but differs in being smaller. having more chambers in the last whorl (usually four and a half to five instead of four), a thinner wall. and a high arched aperture with a distinct lip, it is also distinguished from Globorotalia (T.) continuosa Blow by the difference in the number of chambers in the last whorl, as mentioned above, thinner wall. tangential sutures on the spiral side. and gently curved sutures on the umbilical side.
Occurrence: This species has been found from the upper part of the studied section of the Shimokurosawa Formation and the middle of the Haraichi Formation of the Takasaki area.
References:
Takayanagi, Y., Takayama, T., Sakai, T., Oda, M. & Kitazato, H. (1976). Takayanagi, Y., Takayama, T., Sakai, T., Oda, M. & Kitazato, H. (1976). Microbiostratigraphy of some Middle Miocene sequences in northern Japan. In, Takayanagi, Y. & Saito, T. (eds) Progress in micropaleontology. Micropaleontology Press, New York 356-381. In, Takayanagi, Y. & Saito, T. (eds) Progress in micropaleontology. Micropaleontology Press, New York 356-381. gs
Globorotalia (Turborotalia) rikuchuensis compiled by the pforams@mikrotax project teamviewed: 17-6-2025
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