Doliocapsa weisserti 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 : 129

Doliocapsa weisserti Dumitrică n. sp.

Figs. 11k, k 1

2017 aff. Doliocapsa matsuokai (Yeh) – O’Dogherty, Goričan & Gawlick, p. 17, figs. 8.33-?34.

Description. Shell composed of four segments, conical with the postabdominal chamber much larger than a normal cone. Cephalis small, poreless, separated from thorax by a circumferential row of pores. Thorax and abdomen truncate-conical with vaguely convex margin and dense circular pores arranged alternately in circumferential and oblique rows. Postabdominal chamber much larger than the abdominal one, subglobular, with smooth surface. Its pores are circular, larger than the abdominal ones, polygonally framed and quincuncially arranged. Distal end with a rather large aperture with truncate-conical opening and costate inner contour suggesting a possible very thin terminal cap dissolved after the death.

Studied material. The illustrated specimen.

Holotype. Fig. 11k, k 1 , coll. MGP-PD, stub PD120 - OZ834- R09-03 a.

Dimensions. Length 130 µm, diameter of last chamber 100 µm, inner diameter of aperture 17, outer diameter of distal aperture 33 µm.

Etymology. Dedicated to Prof. Helmut Weissert for his contribution to the knowledge of the anoxic events of the Early Cretaceous.

Remarks. The shape of this species is rather similar to that of the Middle Jurassic (Bajocian to Bathonian) species Hiscocapsa matsuokai Yeh (2009, 2011) from the Snowshoe Formation of east-central Oregon, transferred to the genus Doliocapsa by O’Dogherty et al. (2017). It has in common with this species the number of segments, general shape and the type of the distal aperture. Howev- er, the specimens from the Middle Jurassic of Oregon have deep constrictions and much larger last segments. Other specimens with which it can be compared have been illustrated by O’Dogherty et al. (2016, pl. 8, fig. 33) under the same species name ( Doliocapsa matsuokai ) from the Bathonian-Oxfordian from the Hallstatt Mélange. These specimens differ from the Sardinian specimen by having the first three segments of shell forming a thin and longer conical part without intersegmental constrictions. In our opinion, these different morphotypes of different ages represent different species of the same genus. It is for this reason that we erect a special species for the late Valanginian specimen from Sardinia. No species could traverse such a long period without change of taxonomic identity.

Occurrence. Very rare in Upper Valanginian of S’Ozzastru section.

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).