Hiscocapsa ventriosa 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 : 127-128

Hiscocapsa ventriosa Dumitrică n. sp.

Figs. 11c, c 1 , d, g

1982 Gen. et sp. indet. – Okamura & Uto, pl. 5, fig. 12.

Description. When entire, shell consists of three external morphological parts: a short proximal conical part, a big spherical or ovoid central part, and a distal cap-shaped part. Inner structure not known but supposed to be four-segmented. The proximal conical part consists of a simple cephalis and thorax. Boundary between them and between thorax and abdomen difficult to trace because usually it is not marked by any change in outline. Cephalis smooth-surfaced and generally imperforate. Thorax trapezoidal in outline and short, its pores irregularly disposed. Abdomen large, ovoid with pores of honeycomb structure (fig. 11c). With mature specimens, surface of abdomen is smooth and opening of pores is small and circular due to an external layer of silica that narrows the diameter of pores (fig. 11b, g). For most specimens the abdomen represents the last segment of shell, and its distal part is straight, as if transversally cut. The distal opening of this part is rather large with protruding rim. Complete specimens (fig. 11g) have a hemispherical or inverted cupola-shaped fourth segment that is closed distally; it is thin-walled and easily dissolved or broken off, or not yet built in most specimens.

Studied material. Three specimens in OZ836 and OZ839

and many in the Valanginian of Svinița, Romania.

Holotype. Fig.11c , OZ839, coll. MGP-PD, stub PD120 - OZ836- R08-13 .

Paratype. Fig. 11b , OZ839-coll. MGP-PD, stub PD120 - OZ839- R03-02 .

Dimensions. Length of shell without the fourth segment 164-180 µm, with fourth segment 205-220 µm, maximum diameter of abdomen 124-142 µm.

Etymology. From the Latin adjective – ventriosus, - a, - um – round-bellied.

Remarks. All specimens from the Ozzastru section, although very well preserved, have the last segment dissolved or broken off. To have a complete image and description of the species we included on Fig. 11 the pyritized specimen g from the Valanginian of the Murguceva Formation, Vodinițki valley, Svinița ( Romania), where complete specimens are not rare and very well preserved in pyrite.

Range and occurrence. Valanginian of Sardinia, Japan and Romania.

Figures

Fig. 11 a-b1 - Hiscocapsa grutterinki (Tan): a, OZ834, b, OZ839. c, c1, d, g - Hiscocapsa (?) ventriosa Dumitrică n. sp.: b, OZ839, c, OZ836, c1, aperture, g - complete specimen, V40, Svinița, Romania. e - Doliocapsa utoi Dumitrică n. sp., OZ824. f, f1, h, h1 - Hiscocapsa rugosacutis Dumitrică n. sp., OZ826. i-i1 - Hiscocapsa aitai Dumitrică n. sp., OZ824. p, s -Hiscocapsa lagunculoides Dumitrică n. sp., OZ834, OZ838; p1, s1- distal apertures of both specimens. j - Squinabollum cf. elegans Dumitrică n. sp., OZ826. k, k1 - Doliocapsa weisserti Dumitrică n. sp., OZ834. l - Hiscocapsa tuberculata Dumitrică n. sp., OZ826. m, m1, n - Doliocapsa erbae Dumitrică n. sp., OZ834. o – Doliocapsa favopora Dumitrică n. sp., OZ834. r - Doliocapsa mediterranea Dumitrică n. sp., OZ834. Figs. a-d, j x250; figs. c1, e, e1, f, f1, g, h, i, i1, k, k1, l, p, r x300, m-o, p1 x400.

Fig. 1 Geologic map of the Siniscola area, NE Sardinia (from Dieni & Massari, 1971, updated in 1986). Legend: a - Recent and present alluvial deposits (Holocene). b - Scree deposits (Würm-Holocene). c - Detrital cones mostly composed of gelifraction limestone clasts (“éboulis ordonnés”) (Würm-Holocene). d - Uncemented alluvial cones mostly consisting of limestone clasts (Würm-Holocene). e - Terraced alluvial deposits composed of clasts of basement rocks (Riss?). f - Tightly cemented and dismembered alluvial cones mostly made up of gelifraction limestone clasts (Riss?). g - Cuccuru ’e Flores Conglomerate: polymict, chaotic and thick-bedded breccia and stratified sandstone (middle Eocene). h - Siniscola Marl: grey and grey-yellow marl and, in the upper part, alternating marl/marly limestone with ammonites and very abundant radiolarians and sponge spicules (late Valanginian). i - Schiriddè Limestone: light-brown cherty limestone and limestone with marly interbeds, containing ammonites, radiolarians, sponge spicules and calpionellids (early Valanginian). j - Monte Bardia Limestone: thick-bedded to massive white limestone in places bioconstructed, with corals, nerineids, etc. (early Tithonian - late Berriasian). k - S’Adde Limestone: light-brown to grey fine-grained, well-bedded limestone, condensed with hardgrounds near the base, cherty in the upper part, with ammonites and belemnites in the uppermost part (latest Bathonian - earliest Tithonian). l - Dorgali Formation: well bedded quartz-arenitic and locally ooidal brown dolostone (middle-late Bathonian). m - Crystalline basement (phyllite, micaschist, paragneiss, quartzite, etc.) (Palaeozoic). n - Fault. o - Attitude of beds and schistosity planes. p - Limits of slumped masses of Jurassic formations (Quaternary). q - Concave-upward slip surfaces delimiting rotational slumps (Quaternary). r - Edge of fluvial terrace. s - Quarry. A-A’ Trace of the geological section of Fig. 2. (extracted from Bottini et al., 2018).