Tethysetta ovoidala Dumitrică, 1997

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 : 146-148

Tethysetta ovoidala Dumitrică, 1997

Figs. 15i

1974 Dictyomitra boesii Parona – Riedel & Sanfilippo, p. 778, pl. 4, fig. 6,?5.

1982 Parvicingula boesii (Parona) – Okamura & Uto, pl. 5, figs. 5-7.

1985 Parvicingula boesii (Parona) – Kiminami et al., pl. 1, fig. 9.

1991 Ristola boesii (Parona) – Ishida & Hashimoto, p. 50, pl. 1, fig. 8.

1994 Parvicingula boesii (Parona) gr. – Jud, p. 91, pl. 16, fig.1, non 2 = T. hulla e Dumitrică.

1994 Parvicingula boesii (Parona) gr. – Goričan, p. 80, pl. 24, figs. 11, 14, 15.

1995 Parvicingula boesii gr. (Parona) – Baumgartner et al., p. 402, pl. 3185, figs. 1, 3-6.

1997 Tethysetta boesii (Parona) – Dumitrică et al., p. 48, pl. 10, fig. 19.

1997 Tethysetta ovoidala Dumitrică in Dumitrică et al., p. 50, pl. 10, figs. 21, 22.

2009 Tethysetta boesii (Parona) – Ishii et al., pl. 13, fig. 6.

2014 Tethysetta boesii (Parona) – Robertson et al., fig. 10(A), 28.

2017 Tethysetta boesii (Parona) – Xu & Luo, figs. 6N, 6O.

Remarks. Based on the very well-preserved illustrated specimen from Sardinia and on other similarly well-preserved specimens assigned in the literature to Tethysetta boesii (Parona, 1890) , a more detailed description can be given of the species T. ovoidala which was erected on the basis of partly dissolved specimens from Oman (Dumitrică et al., 1997). This species has spindle-shaped test of about 9-10 segments consisting of two main parts: a proximal conical part and a cingulate middle and distal part. Proximal conical part is smooth-surfaced with small circular pores disposed in more or less circular rows. This regular disposition increases distally, and in the same direction also the size of pores increases. Apex of cephalis thin-walled, usually dissolved. This portion seems to comprise the first four segments. Boundaries between segments are not marked by any change in outside morphology excepted, in some cases, the appearance of very small nodes at the boundary between abdomen and postabdominal segments. The following 4-5 segments increase in diameter, whereas the following (last?) ones decrease forming an inflated spindle-shaped shell. The intersegmental boundaries are well marked by high circumferential ridges that may be smooth or more or less nodular. Segments of this part are very depressed, concave in outline, with three rows of alternatively disposed pores. Pores of middle part of segments are elliptical with protruding rims. These rims merge together at the proximal and distal ends of pores to join on the intervening bars of the proximal and distal circumferential rows of pores of each segment. In the middle row of pores this structure forms a circumferential band with elliptical pores separated by more or less disturbed(?) rectangular depressions. Last segments are rarely preserved due probably to dissolution because they are very thin.

Material. Only the illustrated specimen.

Studied material. Specimen of Fig. 15i , coll. MGP-PD, stub PD120-OZ834-R10-29.

Dimensions. Length more than 240 μm, maximum diameter 125-160 μm.

Remarks. By its shape, number of segments, type of middle row of pores with protruding rims at the segments with strong circumferential ridges, the specimen illustrat- ed by Ishida & Hashimoto (1991) as Ristola boesii (Parona) from the Lower Cretaceous of the Chichibu Terrane in eastern Shikoku ( Japan), belongs to this species. It differs from the specimen herein illustrated especially by having very thick circumferential ridges.

Morphologically, this species is very close to Tethysetta boesii (Parona, 1890) to which it was usually assigned, but differs by having a larger maximum diameter relative to its length. T. boesii is much slender and its intersegmental boundaries of proximal segments are also well marked by high circumferential rings.

Tethysetta ovoidala is also close to T. usotanensis (Tumanda, 1989) , from which it differs by the regularity of disposition of pores and the quite perfect bilateral symmetry relative to a perpendicular plane passing through the middle of shell. T. usotanensis has the conical apical part of shell longer than the lower part and the maximum diameter is not at the middle part of the shell but at its third distal part.

Range and occurrence. Latest Tithonian to Hauterivian (see synonymy). Upper Valanginian of Sardinia, and probably Valanginian of Japan.

Figures

Fig. 15 a - Pseudodictyomitra nodocostata Dumitrică, OZ839. b-e - Tethysetta usotanensis (Tumanda): b - OZ837, c, d - OZ836, c1 - details of pore morphology, e - OZ838. f-h - Tethysetta reducta Dumitrică n. sp.: f - OZ836, g - OZ839, h - OZ834. i - Tethysetta ovoidala Dumitrică, OZ836, i1 - details of pore morphology. j-l - Tethysetta cingulifera Dumitrică: j - OZ838, k, l - OZ839. m - Favosyringium affine (Rüst), OZ834. n - Favosyringium cf. affine (Rüst), fragment of shell, OZ836. o - Favosyringium quadriaculeatum Steiger, fragment of shell, OZ838. p-t - Pseudoxitus seriola Dumitrică: p - OZ839, r-t - OZ836. Figs. a-I, m-t x250, figs. j-l x300.