Excentrodiscus kamikurii, Dumitrica, 2019

Dumitrica, Paulian, 2019, Cenozoic Spumellarian Radiolaria With Eccentric Microsphere, Acta Palaeontologica Romaniae 15 (1), pp. 39-60 : 53-54

Excentrodiscus kamikurii nov. sp

Figures 9f, g

cf. 2015 Excentrodiscus aff. oculatus (Ehrenberg) . – Kamikuri, p. 148, pl. 15, figs. 3, 4, 6, 8.

Description. Microsphere very small, eccentrical, with 8- 10 wide polygonal pores interconnected to outer medullary shell through 8-10 very thin beams of various length depending of their position in shell. Outer medullary shell spherical, rather thin and latticed with polygonally framed circular pores. Intervening bars thin, triangular in transverse section. Cortical shell spherical, rather thin-walled with numerous circular pores. Intervening bars thin with sharp crests and short and thin by-spines at vertices. Cortical shell bears 8-10 needle shaped spines about as long as skeleton ray. These spines are originated either in the microsphere or in the wall of the outer medullary shell, no one in the cortical shell.

Material. One specimen in sample DODO 123 D.

Holotype. The illustrated specimen, individual slide, coll. MGL 103563 …

Dimensions. Diameter of microsphere 16-17 μm, of outer medullary shell 57 μm, of cortical shell 125 μm.

Etymology. The species is named for Dr. Shin-ichi Kamikuri, Ibaraki University, Japan, for his contribution to the knowledge of Cenozoic radiolarians and for having illustrated some specimens of Eocene Excentrodiscus .

Remarks. Shell of this species resembles the shell of the co-occurring species in sample DODO 123D from which it differs in having radial spines. It resembles very much the Recent species Excentrodiscus echinatus Hollande & Enjumet from the Gulf of Alger in shape and size of shells from which it only differs in having a smaller number and shorter spines. The specimens illustrated by Kamikuri (2015) as Excentrodiscus aff. oculatus (Ehrenberg) are rather similar to this new species from whom they differ especially in having shorter spines.

Range and occurrence. Middle? Eocene of Indian Ocean.

Figures

Fig. 9 a – Heliodiscus riedeli nov. sp, specimen broken and repaired during life, PROA 96P. b - Helioferrusa hollandei nov. gen., nov. sp., holotype, scale bar = 100 μm; h – portion of shell more magnified, PROA 96P; c – Helioferrusa hollandei nov. sp., paratype, scale bar = 100 μm; i – portion of shell more magnified, DSDP 21-205-7-1, 70-72 cm. d, e – Excentrodiscus dodo nov. sp., holotype, focused on surface of cortical shell and half sectioned showing the outer medullary shell and the eccentric microsphere, DODO 123 D, scale bar = 50 μm. f, g – Excentrodiscus kamikurii nov. sp., partly sectioned showing the outer medullary shell, the eccentric microsphere, and the cortical shell, respectively; g – same, overturned showing the cortical shell, a spine is blocked in the pore of a nassellarian Sethochytris sp., DODO 123D, scale bar = 50 μm.