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Current identification/main database link: Globorotalia tosaensis Takayanagi & Saito 1962
Test free, spiral side flat to slightly concave, umbilical side strongly convex, with rather deep and open umbilicus, periphery subacute, peripheral outline only slightly lobulate in adult, but more lobulate in younger tests: chambers low and broad on spiral side. increasing gradually in size as added, commonly with four chambers in final whorl, chambers on umbilical side sloping sharply outward to periphery from rounded umbilical shoulder, giving test a conical appearance: sutures somewhat indistinct on spiral side, gently curved, flush or very slightly depressed, sutures on umbilical side depressed, nearly radial in early part of whorl, later becoming somewhat sigmoidal: wall calcareous, finely perforate. surface generally spinose, especially in early chambers and umbilical shoulders of later chambers except for last formed one on umbilical side, resulting in a granular appearance; peripheral margin in early chambers rather smooth and transparent in appearance, but not forming a keel or marginal thickening; aperture a very low interiomarginal, umbilical-extraumbilical arch, bordered above by a narrow lip.
Size: Maximum diameter of holotype 0.41 mm., maximum thickness 0.34 mm. Maximum diameter of paratype 0.39 mm., maximum thickness 0.29 mm.
Extra details from original publication
Remarks. Globorotalia tosaensis Takayanagi and Saito resembles Globorotalia truncatulinoides (d'Orbigny) in general appearance, but has less chambers in a whorl, and less acute periphery which is not keeled or thickened . In addition, G. truncatulinoides has an imperforate layer on the thickened margins of the last few chambers, besides the peripheral keel. These differences in character between both species are very similar to those among the subspecies of Globorotalia fohsi Cushman as pointed out by Banner and Blow (1959, Palaeontology. vol. 2, no. I, p. 21). They assumed the gradation from forms without keels to those with pseudocarinae, and from these to forms with true carinae is a distinct character generally seen in the evolutional series of the Globorotaliids. The present relationship between G. tosaensis and G. truncatulinoides may be an analogous case. The latter species appears to have developed from G. tosaensis by attaining the characters mentioned above.
Blow, W. H. (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In, Bronnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967. E J Brill, Leiden 380-381. gs Takayanagi, Y. & Saito, T. (1962). Planktonic foraminifera from the Nobori formation, Shikoku, Japan. Science Reports of the Tohoku University, Series 2 (Geology). 2(5): 67-105. gs
Blow, W. H. (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In, Bronnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967. E J Brill, Leiden 380-381. gs
Takayanagi, Y. & Saito, T. (1962). Planktonic foraminifera from the Nobori formation, Shikoku, Japan. Science Reports of the Tohoku University, Series 2 (Geology). 2(5): 67-105. gs
Globorotalia tosaensis compiled by the pforams@mikrotax project team viewed: 15-4-2021
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