Squinabollum elegans 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 : 134-135

Squinabollum elegans Dumitrică n. sp.

Figs. 12p, r, t, v

?1982 Theocapsa sp. – Okamura & Uto, pl. 3, fig. 14.

1982 Sethocapsa sp. – Okamura & Uto, pl. 6, fig. 9.

Description. Shell conical, three-chambered, each chamber of different morphology. Cephalis imperforated, two-chambered, armed with a short or very short conical horn, with chambers separated usually from one another by a circumferential circle of extremely small pores, and sometimes by a shallow constriction. Thorax ring- or collar-shaped with parallel or subparallel margins, larger and a little higher than cephalis, and with distal part submerged in the abdominal cavity. Its wall is perforated by very small, sparse and irregularly distributed pores, sometimes with a somehow spongy structure. Due to its spongy structure, the thorax of some specimens appears brighter than the other segments on scanning electron micrographs. Abdominal chamber spherical, large, with wide circular pores. On the inner side, the pores have smaller diameter and on the outer side they are larger, cylindrical and polygonally (hexagonally or pentagonally) framed on the surface. Interporal bars with relatively sharp crests and rarely with one or two very short spines. Distal end of postabdomen without aperture.

Studied material. The description is based on 8 specimens from samples OZ824, OZ825, OZ826, OZ836, plus the two specimens illustrated by Okamura & Uto ( 1982) from the Lower Cretaceous (probably Valanginian) chert sample YK-546 from the Yokonami Mélange of Shimanto Belt, Japan .

Holotype. The specimen of figure 12v, sample OZ836, coll. MGP-PD, stub PD120 -OZ836- R08-19 .

Paratype. Fig. 12t , sample OZ836, coll. MGP-PD, stub PD120 - OZ836- R08-12 .

Dimensions. Length of shell 143-192 µm, of cephalis with apical horn 43-83 µm, of thoracic collar up to 27 µm, diameter of collar-shaped thorax 38-60 µm, of abdomen 90-144 µm.

Etymology: From the Latin elegans = elegant, due to the perfect and beautiful shape of the holotype.

Remarks. This new taxon is very well distinguished from other congeneric species by the special shape of its thorax resembling a necklace or a comforter. The specimens from Sardinia resemble very well the probably coeval specimens illustrated by Okamura & Uto ( 1982).

Range and occurrence. Upper Valanginian, S’Ozzastru section, and Valanginian from the Yokomani Mélange of Shimanto Belt, Japan.

Figures

Fig. 12 b - Crococapsa cf. horokanaiensis (Kawabata), OZ834. a, c, d - Crococapsa zweilii (Jud): a, OZ826; c, OZ836; d, OZ825. e-h - Crococapsa uterculus (Parona): e, f, h - OZ834, g - OZ825. i-o - Ocellicapsa ruthae Dumitrică n. sp.: i - OZ837, j - OZ837, k - OZ836, i - OZ834, m - OZ824, n - OZ838, n1 - detail of cephalothoracic body, arrow shows the place of very small pores at the boundary between the two parts of cephalic cavity, o - OZ825. p, r, t, v - Squinabolum elegans Dumitrică n. sp.: p - OZ824, r - OZ826, t - OZ836, s - Amphipyndax zyabrevi Dumitrică n. sp. - OZ825. u - Campanomitra pulchella (Rüst), OZ836. v - OZ834. w, x - Archaeodictyomitra inflata Dumitrică n. sp.: w - OZ839, x - OZ834. Figs. a, c-h, u x250, all the others x300.