Pseudoxitus seriola 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 : 150-151

Pseudoxitus seriola Dumitrică, 1997

Figs. 6d , 15 p-t

1982 Xitus gifuensis Mizutani – Adachi, pl. 3, fig. 1, non 2.

1982 Novixitus sp. – Okamura & Uto, pl. 2, figs. 7, 9 non 8.

1989 Xitus gifuensis Mizutani – Tumanda, p. 40, pl. 4, fig. 5.

1991 radiolari – Dieni & Massari, fig. 23d.

1995 Neorelumbra (?) sp. B. – Kiessling, p. 338, fig. 8/10.

1997 Pseudoxitus seriola Dumitrică in Dumitrică et al., p. 61, pl. 13, figs. 12, 15.

1997 Pseudoxitus omanensis Dumitrică in Dumitrică et al., p. 61, pl. 12, figs. 13, 14, 18.

2009 Pseudoxitus seriola Dumitrică – Ishii et al., p. 347, pl. 17, figs. 13-15, non 11, 12.

2017 Pseudoxitus angulatus Dumitrică – Xu & Luo, Fig. 8A .

Description. Shell low conical of four to six segments. Cephalis hemispherical or rounded conical with very small pores or without pores, separated from the thorax by a circle of larger pores. Collar boundary marked by such larger pores or also by the change of the angle of the sides of the cone. Thorax is a truncated cone with wall perforated by very small circular pores and, at its base, with three or four tubercles visible on half the perimeter. Abdomen larger than thorax but not higher, consisting of a circumferential row of big tubercles, about five on half the perimeter. Tubercles with massive apex, without pores. Lumbar boundary marked by a constriction between the row of tubercles of thorax and that of the abdomen. Generally, the septal tubercles are not visible, but they are very rare and very small in some specimens. First postabdominal chamber larger and higher than the abdominal one, continuing in straight line the conical outline of the shell and having two circumferential rows of big tubercles with usually poreless apex. Tubercles of the two rows in intercalated position with respect to one another. Below the lowermost row of tubercles, the shell become inverted conical on a very short distance before stopping its growth or can bear a row of smaller septal tubercles. Base flat with circular pores and with a wide circular aperture. Rare specimens can have a distal chamber of small diameter and with a row of small tubercles (holotype).

Studied material. Many specimens.

Dimensions. Length 176-200 µm, diameter 138-160 µm.

Remarks. The taxonomy used by Dumitrică when he studied the fauna from Oman (Dumitrică et al., 1997) was purely morphological, due to the small number of specimens at disposal. In this group he recognized several species based on the shape of shell, number of segments and others. At present, combining the data from Oman with those from Sardinia and those published in the meantime, the variability and morphological boundaries of the species may be better understood. The specimen from Fig. 15r belongs to this species by size and shape of skeleton, although the two rows of nodes of the last segment and the deep postlumbar stricture are very weekly marked.

Occurrence. Valanginian of Sardinia, Oman, North Pacific and 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.

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.

Fig. 8. a - Becus coronatus Dumitrică n. sp., OZ839. b-f1, j - Becus triangulocentrum Dumitrică, b - OZ836; c - same, lateral view, d - OZ836. e, f - OZ825, f1 - lateral view of fig. f. g - Alievium regulare (Wu & Li), OZ836. h, i, k, l - Alievium rotundum Dumitrică n. sp.: h, specimen destroyed showing internal structure, OZ836; i - OZ836, k, l - holotype, OZ834. m - Alievium incomptum Dumitrică n. sp., OZ836. n - Godia (?) lenticulata Dumitrică n. sp., OZ834. o - Godia (?) lens Dumitrică n. sp., OZ825. p - Alievium eurasicum Dumitrică n. sp., OZ825. r - Microsandwichia plana (Hori), OZ834. s, t - Spumellarian gen. et sp. indet., OZ834. figs. c, e-h, k, m, r, t x250, figs. a, b, d, i, j, l, p, s x300; figs. n, o, t x400.