Ristola, Pessagno and Whalen, 1982

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 : 145

Ristola (?) nakatonbetsensis Tumanda 1989

Fig. 6g

1989 Ristola nakatonbetsensis Tumanda , p. 31, pl. 4, figs. 7, 8.

1991 radiolari – Dieni & Massari, p. 36, fig. 23g.

Material. A single specimen illustrated by Dieni & Massari (1991).

Dimensions. Length 176 µm, maximum diameter 132 µm.

Remarks. By comparison with the holotype from the Lower Cretaceous Furebira Formation ( Japan), the conical specimen illustrated by Dieni & Massari seems to represent only the proximal half of the shell. What is characteristic of this species is that the secondary outer layer of the proximal part of shell has continuous costae similar to those of the Archaeodictyomitridae .

Range and occurrence. Very rare in the upper Valangini- an of Sardinia and also in the probable Hauterivian of the Furebira Formation, Japan.

Figures

Fig. 6 Radiolarians illustrated by Dieni & Massari, 1991 in their Fig. 23c-i which correspond to the letters from that article: c - Favosyringium affine (Rüst), d - Pseudoxitus seriola - Dumitrică, e - Williriedellum peterschmittae Schaaf, f - Cryptamphorella Dumitricăi Schaaf, g – Ristola nakatonbetsensis Tumanda, h - Crococapsa zweili (Jud), i - Cryptamphorella circumthoracica Dumitrică n. sp., Fig. c x200, figs. d-i x250.