Amphipyndax zyabrevi 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 : 135

Amphipyndax zyabrevi Dumitrică n. sp.

Fig. 12s

1996 Amphipyndax stocki (Campbell & Clark) – Zyabrev, pl. 2, figs. 11, 12.

Description. Shell bottle-shaped consisting of five or more segments difficult to distinguish from the external shape, with a conical proximal half and a cylindrical distal half. Cephalis spherical outside imperforate, without apical horn and with distal part covered by the proximal part of the thoracic skeleton. Thorax, abdomen and probably first postabdominal segment form a conical part with no intersegmental constriction outside. Following segments form a cylindrical body with one visible constriction in the middle part and another one on the distal part. The latter is not preserved but marked by a fastdecreasing trend in diameter. Wall of post-cephalic test perforated by dense cylindrical pores with dense honeycomb shape arranged quincuncially in transverse and oblique rows. They are hexagonally framed in the distal half and tend to be gradually elongate in proximal direction so that in the vicinity of cephalis they become longelliptical.

Studied material: Only one specimen.

Holotype. Fig. 12s , sample OZ825, coll. MGP-PD, stub PD120 -OZ825- R12-15 .

Dimensions. Length of preserved test 127 µm, maximum diameter 76 µm.

Etymology. The species is dedicated to Dr. Sergey V. Zyabrev, from the Institute of Tectonics and Geophysics, Habarovsk ( Russia), who illustrated a similar species.

Remarks. The specimen found in the Sardinian sample preserves most part of the test and resembles almost perfectly the specimens determined by Zyabrev (1996) as Amphipyndax stocki and coming from what he considered as an Albian-Cenomanian assemblage from an accretionary complex of the Russian continental Far East. The specific determination is erroneous because A. stocki (Campbell & Clark, 1944) has another morphology: larg- er pores and, usually, boundary between segments marked by constrictions.

Range and occurrence. Late Valanginian to probably Aptian or Albian if we consider correct the age determined by Zyabrev for his Amphipyndax stocki .

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.