Archaeodictyomitra humerosa 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 : 139

Archaeodictyomitra humerosa Dumitrică n. sp.

Figs. 13s ; 14b, f

?1992 Archaeodictyomitra pseudoscalaris (Tan Sin Hok) – Matsuoka, pl. 1, fig. 8.

Description. Shell conical with three parts when complete: a narrow conical apical part consisting of 2-3 segments of which the distalmost has a convex outline, a wider truncated conical middle part consisting of 3-5 segments with convex outline and separated from one another by constrictions, and a last narrow distal cylindrical segment.

Studied material. Three illustrated specimens in OZ826 plus many others not figured (see Table 1).

Holotype. Figure 14b , coll. MGP-PD, stub PD120 - OZ834- R10-27 .

Paratype. Figure 13s , coll. MGP-PD, stub PD120 - OZ839- R01-09

Dimensions. Length of complete test 216 µm, of apical conical part 66 µm, of complete middle part 123-133 µm, of distal neck-shaped segment 27 µm, maximum diameter of test 98-116 µm.

Etymology. From the Latin humer = shoulder, due to the shape of the test at the contact between the first and the middle part.

Remarks. This species, as here defined, has a rather wide variability. It comprises specimens with 6 to 10 segments and the entire test consists of three parts: a conical proximal part, a middle trapezoidal part, and a distal narrower part. The proximal part consists commonly of the first 3-4 segments, which are not separated by well-marked constrictions. The middle part consists of 3-5 segments with well-marked convex outline which gives this part an undulate aspect. On this part, the boundaries between segments are situated at the expanded portion of test and are usually marked by a circumferential row of larger, usually transversally elongated pores situated just below the boundary platforms ( Figs. 13s , 14b, f ). The third part, observed only in a single specimen ( Fig. 14b ), is represented by a cylindrical neck-shaped segment. The surface of the whole test comprises 10-11 narrow uninterrupted costae on half the perimeter separated by wide intercostal spaces. Pores are small and arranged in a single irregular row in each intercostal depression, rarely in two irregular rows ( Fig. 14f ).

Range. Berriasian to early Hauterivian.

Figures

Fig. 13 a, b - Apiaromitra apiarium (Rüst): a - OZ836, b - OZ839, a1 - detail of ornamentation of last segment, b1 - detail of ornamentation of penultimate segment. c - Archaeodictyomitra robustovum Dumitrică n. sp., OZ837. d - Archaeodictyomitra sp., OZ839. e, f - Archaeodictyomitra mitra Dumitrică: e - OZ838, f - OZ824. g-k - Archaeodictyomitra massarii Dumitrică n. sp.: g - OZ834, g1 - detail of surface x1000. h - OZ834, i - OZ839, j - OZ834, k - OZ839; k1 - detail of wall showing the cavernous structure, k2 - detail of surface. l, p - Archaeodictyomitra longipora Dumitrică n. sp., OZ836; l - portion of surface of p much magnified showing the elevated intercostal area. m - Apiaromitra tyaughtonensis (Cordey), OZ837. n, t - Archaeodictyomitra dienii Dumitrică n. sp.: n - OZ836, t - OZ837. o - Thanarla cf. pulchra (Squinabol), OZ824. r - Archaeodictyomitra judae Dumitrica n. sp., OZ839. s - Archaeodictyomitra humerosa Dumitrică n. sp., OZ839. Figs. a, b x250, k1 and k2 x450, all the others x300.

Fig. 14 a - Archaeodictyomitra conicoscalaris Dumitrică n. sp., OZ839. b, f - Archaeodictyomitra humerosa Dumitrică n. sp.: b - OZ834, f - OZ824. c - Archaeodictyomitra pumila Dumitrică n. sp., OZ834. d, e - Archaeodictyomitra conica (Aliev), OZ824. g - Thanarla cf. pulchra (Squinabol), OZ825. h - Thanarla pulchra (Squinabol), OZ839. i, j – Mictyoditra thiensis (Tan), OZ836. k - Archaeodictyomitra excellens (Tan), OZ839. l - Archaeodictyomitra sp., OZ836. m, n - Loopus nudus (Schaaf): m - OZ838, n - OZ834. o - Loopus cf. primitivus (Matsuoka & Yao), OZ834. p, p1, p2 - Svinitzium depressum (Baumgartner), p1, p2 - details of penultimate segmental band showing relic pores of parvicingulid type or other types, OZ824. Figs. r, t - Svinitzium (?) irregulare Dumitrică n. sp.: r - OZ 836, t - OZ834. s, u - Pseudodictyomitra cf. carpatica (Lozynyak): s - OZ834, u - OZ 824. Figs. b, n x250, the others x300.