Heliodiscus riedeli, Dumitrica, 2019

Dumitrica, Paulian, 2019, Cenozoic Spumellarian Radiolaria With Eccentric Microsphere, Acta Palaeontologica Romaniae 15 (1), pp. 39-60 : 52

Heliodiscus riedeli nov. sp.

Figures 8b, e, f ; 9a

Description. Shell large, disc-shaped with a small double medullary shell and a wide cortical shell. Microsphere very small, eccentric in the outer medullary shell and connected to it through a few cylindrical beams of different length. Outer medullary shell spherical or slightly prunoid with wide circular or polygonal pores separated by thin intervening bars and included in the cavity of the cortical shell to which it is connected with the two faces of this shell by a bunch of very short rays. Cortical shell flat, very thin and perforated by numerous very small polygonal pores arranged either disorderly or, partly, radially. Periphery of disc armed with numerous threebladed, short, and pyramidal spines disposed in several planes.

Material. Eight specimens in sample PROA 96 P, 241- 243 cm, late middle Miocene .

Holotype. Figure 8b , coll. MGL 103559 .

Dimensions. Diameter of microsphere 17-19 μm, of outer medullary shell 47-54 μm, of cortical shell 241-295 μm.

Etymology. The species is named for William R. Riedel for his great contribution to the study of Cenozoic radiolarians. It is also in the sample provided by him that this species was found.

Remarks. This species differs from all the other species of this genus in having a large, completely flat disc-shaped cortical shell and many short pyramidal spines on periphery.

Range and occurrences. Late middle Miocene, central Pacific.

Figures

Fig. 8 a, c - Excentrococcus annulatus Dumitrică; a – mature specimen, face view, DSDP 21-205-7-1, 70-72 cm, scale bar 100 μm; c – other specimen, transversal section along the longitudinal axis showing the eccentric microsphere, DSDP 21-206-29CC, scale bar = 100 μm. b, f, g - Heliodiscus riedeli nov. sp., PROA 96P. d, e, h – Heliodiscus bipolaris nov. sp. focused at centre, on surface, and in lateral view, respectively, scale bar = 50 μm, DSDP 21-206-29CC.

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.