Praeconocaryomma thurowi Dumitrică, 2022

Dumitrica, Paulian, Dieni, Iginio & Massari, Francesco, 2022, Valanginian Radiolarians Of Ne Sardinia (Italy) In The Frame Of The Weissert Event, Acta Palaeontologica Romaniae 18 (2), pp. 97-159 : 110

Praeconocaryomma thurowi Dumitrică n. sp.

Fig. 7r

1982 Praeconocaryomm a sp. – Okamura & Uto, pl. 4, fig. 1, non 2.

1988 Conocaryomma sp. A (cf. Praeconocaryomma sp. A in Pessagno 1977b – Thurow, p. 399, pl. 9, fig. 5.

Description. Shell spherical with characteristic triangular meshes. Meshes small and nodes of the network are usually small and only some are higher developing a beginning of three-bladed spines marked by three-bladed pyramidal elevation. Number of layers difficult to establish, visible being only two or three externalmost layers.

Studied material. One specimen in Sardinia section (the holotype), plus the specimen illustrated by Thurow .

Holotype. Figure 7r , coll. MGP-PD, stub PD120 -OZ836- R08-27 .

Dimensions. Diameter 107-133 μm.

Etymology. The species is dedicated to J. Thurow who illustrated a rather similar specimen from the Hauterivian-lower Aptian radiolarian assemblages of North Atlantic. Similar specimens were also illustrated from the Lower Cretaceous sequence of chert in the Yokonamy Mèlange of the Shimanto Belt, Japan.

Remarks. This taxon differs from Praeconocaryomma copiosa Wu by smaller size of the triangular meshes of the cortical shell and by development of some very short three-bladed elevations as bases of eventual short spines.

Range and occurrence. Very rare in the upper Valangini- an of Sardinia and in the probably upper Valanginian from Japan and upper Hauterivian-lower Aptian of North Atlantic area according to Thurow (1988).

Figures

Fig. 7 a - Praeconosphaera sphaeroconus (Rüst OZ826. b-d - Praeconosphaera antiqua (Parona): b - OZ834, c - OZ838, d - OZ825. e - Tritrabs ewingi (Pessagno), arm in lateral view, OZ836. f-h - Emiluvia chica Foreman, OZ836; f - face view, g - lateral view from a spine, h - lateral view of a broken specimen showing the medullary test. i - Pantanellium sp. 1, OZ825. j, l-n1 - Pantanellium squinabolli (Tan): j - OZ834; l, m - OZ834, n - OZ836; m1, n1, details of inner wall of pores. k - Pantanellium sp. 2, OZ834. o – Pantanellium cf. squinaboli (Tan), OZ836; p - Praeconocaryomma copiosa Wu, OZ836. r - Praeconocaryomma thurowi Dumitrică n. sp., OZ836. s, t - Triactoma tithonianum Rüst, side views; s - OZ834, broken off specimen showing medullary shell; t - OZ825, equatorial view, t1 – face view; s1, t2 - detail of the base of spines of figs. s and t, respectively, x800. Figs. a-h, l-n x200; i-k, o-r x300; s, t x400, m1, n1 x500.