Excentrodiscus dodo, Dumitrica, 2019

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

Excentrodiscus dodo nov. sp.

Figures 9d, e

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

Description. Cortical shell small, spherical with numerous circular pores. Pores equal, hexagonally framed, rarely pentagonally framed. Intervening bars triangular in transverse section forming crests. At vertices of frames test develops very small pointed thorns that make the surface of test rough. Inside cortical shell there is a spherical double medullary shell with an eccentric microsphere. Microsphere with a few polygonal pores and connected to outer medullary shell through very thin radial beams of different length depending of their position. They stop in the wall of outer medullary shell. Outer medullary shell spherical, thin-walled with polygonally framed circular pores. This shell gives rise to many thin radial bars that connect it to cortical shell.

Material. One specimen in sample DODO 123 D.

Holotype. The illustrated specimen, individual slide, stored in the MGL 103562 .

Dimensions. Diameter of microsphere 18 μm, of outer medullary shell 55 μm, of cortical shell 122 μm.

Etymology. The species is named after the sample DODO of the Scripps Institution of Oceanography, California, in which the species was found.

Remarks. The shell of Excentrodiscus dodo resembles that of E. kamikurii nov. sp. in size and thickness of shell, but differs from it in not having spines, and in the fact that the beams connecting the microsphere with the outer medullary shell are not aligned with those connecting the latter with the cortical shell. It resembles also the middle/late Eocene specimens determined by Kamikuri (2015) as Excentrodiscus aff. oculatus (Ehrenberg) by not having long spines and by the type of cortical pores.

Range and occurrence. Middle? Eocene, DODO 123 D, Central Indian Ocean Basin.

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.