Helioferrusa hollandei, Dumitrica, 2019

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

Helioferrusa hollandei nov. sp.

Figures 9b, c, h, i

Description. Shell thin disc-shaped consisting of 4 shells: a double medullary shell with an eccentric microsphere, a large main cortical shell, and a peripheral equatorial ring. Microsphere very small, eccentric in the outer medullary shell. Outer medullary shell prunoid or subspherical, with large circular or polygonal pores and included in the cavity of the cortical shell with whom it is connected to the two faces of the latter by a bunch of oblique radial beams. These beams do not cross this shell. Cortical shell large, disc-shaped or lenticular and a little thicker than the diameter of the outer medullary shell. It has numerous very small circular to oval pores of various sizes and irregularly or, partly, radially disposed. This shell is surrounded by a peripheral ring with similar pores but usually smaller. Inside this ring there are radial costae that divide its circumference in unequal segments. Periphery of ring with tiny thorns.

Material. Four specimens, from the late middle Miocene sample PROA 96P.

Holotype. The illustrated specimen, coll. MGL 103561 .

Dimensions. Diameter of microsphere 17-19 μm, of outer medullary shell 49-54 μm, of cortical shell 173-232 μm, of peripheral ring 232-330 μm.

Etymology. The species is dedicated to André Hollande, co-author of the valuable monograph on living Radiolaria from the Gulf of Alger.

Remarks. In this species I included two morphotypes: one found in sample PROA 96P ( Fig. 9b ), represented by 7 specimens, the other one in sample DSDP 21-205-7-1, 70-72 cm from South Fiji Basin, which is late Miocene (NN10 Zone) in age ( Fig. 9c ). These two morphotypes are practically contemporaneous but morphologically rather different. The morphotype from the sample PROA 96P has the cortical shell flat, very thin similar to that of Heliodiscus riedeli nov. sp., and the peripheral ring has thin intervening bars between pores. The morphotype from the sample DSDP 21-205-7-1, 70-72 has the lenticular cortical shell, with rather convex faces and larger pores, and the peripheral ring has much smaller pores, separated by larger intervals, approximately as large as diameter of pores. These differences seem to be rather important, at least at subspecies level, but because I found a single specimen with such characters in that sample I do not know what signification they could have.

Range and occurrence. Late middle Miocene from tropical and subtropical Pacific.

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.