Archaeodictyomitra judae 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 : 138-139

Archaeodictyomitra judae Dumitrică n. sp.

Fig. 13r

1927 aff. Stichomitra pseudoscalaris Tan Sin Hok , p. 56, pl. 11, fig. 84.

1981 aff. Archaeodictyomitra pseudoscalaris (Tan Sin Hok) – Schaaf, p. 432, pl. 4, fig. 5; pl. 21, figs. 13a, b.

1988 aff. Archaeodictyomitra pseudoscalaris (Tan Sin Hok) – Thurow, p.398, pl. 7, fig. 14.

1989 aff. Archaeodictyomitra pseudoscalaris (Tan Sin Hok) – Tumanda, p. 36, pl. 3, fig. 12.

1994 Dictyomitra pseudoscalaris Tan sensu Schaaf – Jud, p. 75, pl. 9, figs. 6, 7.

1994 aff. Dictyomitra communis (Squinabol) – O’Dogherty, p. 71, pl. 1, figs. 3, 4, non 5-11.

2009 aff. Archeaodictyomitra leptocostata Dumitrică – Ishii et al., p. 343, pl. 11, fig. 1.

Description. Shell conical of 8-11 segments and 11-12 costae visible on half a perimeter. Apical part, consisting of three and a half segments, conical with straight outline and intersegmental boundaries marked by a row of pores. Starting from the distal half of the fourth segment and proximal part of the fifth one, the test increases rapidly in diameter and brcomes strongly undulated. On this part the rows of intersegmental pores are at first on the highest parts of ondulations and then move gradually distally below them. Diameter of segments increases slowly up to the seventh segment and decreases a little in the last one.

Studied material. The figured specimen from sample OZ839, coll. MGP-PD, stub PD120 -OZ839- R01-09 , and other 12 specimens in OZ838 and 10 in OZ839, not illustrated .

Dimensions. Length of test 216 µm, maximum diameter of the seventh segment 106 µm.

Etymology. The species is dedicated to Ruth Dumitrică- Jud who illustrated a specimen similar to the holotype of this species.

Remarks. This species has affinities with Archaeodictyomitra pseudoscalaris (Tan Sin Hok, 1927) in which it probably originated and from which it differs by having well lobular shell starting with the first postabdominal segment. It resembles perfectly the specimen illustrated by Jud (1994, pl. 9, fig. 7) from the upper Hauterivian of the Fiume Bosso section (Marche region, Italy), with the only difference that it is a little shorter. It seems that at the horizon OZ838 started the evolution of this species from A. pseudoscalaris because the specimens occurring in lower beds have the test very little constricted and with the proximal part difficult to separate from the rest of the skeleton. The holotype of Archaeodictyimitra pseudoscalaris (Tan) differs from this new species by having very slightly lobular segments and a convex outline, and more pores in each intercostal zone of segments. By having constrictions, the new taxon, as well as A. humerosa Dumitrică n. sp. (see above), resembles the genus Dictyomitr a Zittel, 1876, emend. Pessagno, 1976. However, both species differ from the congeneric species because their constrictions do not completely coincide with the intersegmental boundaries, especially in the middle part of test. From A. humerosa Dumitrică n. sp., A. judae differs by being narrower, by having larger pores on the sutural row of pores and only one or maximum two pores per segment in each intercostal area, plus more advanced constrictions of test. Another similar species is A. coniforma Dumitrică 1997 that differs from A. pseudoscalaris by being perfectly conical and much slender.

O’Dogherty (1994, pl. 1, figs. 3-11) considered A. pseudoscalaris very variable and included it in a long list of synonyms of the species Dictyomitra communis (Squinabol) . To prove this high variability he illustrated 9 specimens, all from the same locality and of the same age (late Aptian). We retain as D. pseudoscalaris only the first two specimens from his plate (figs. 3, 4) that differ from the other ones by having the last segment narrower and the lateral outline of test visibly convex, resembling the holotype. The other specimens are conical with rather straight lateral sides and resemble the holotype of Dictyomitra communis (Squinabol 1904) .

Range and occurrence. Upper Valanginian to upper Apti- an of Tethys according to Jud ( 1994) and O’Dogherty ( 1994).

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.