Eucyrtidiellum sardoum 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 : 114

Eucyrtidiellum sardoum Dumitrică n. sp.

Figs. 9a, a 1 , b

Description. Shell conical of three segments separated by rather well marked constrictions. Cephalis smooth subglobular or conical with a very short apical spine and a visible ventral pore at the boundary with thorax. Thorax poreless, truncate conical and smooth or with up to 14 longitudinal costae on half the perimeter. Costae very slightly visible to well developed. Abdomen globular, poreless except for distal part, and smooth, or with 6-12 longitudinal costae, usually developed on its proximal half. Lumbar constriction marked by 6-12 pores on half the diameter. Distal end of abdomen with a circular band of pores arranged usually in two irregular circles one of which is external, on the lateral part of the abdomen, and the other one on the base of this segment. Distal part of abdomen planiform, with a large circular aperture. Postabdominal segment not preserved.

Studied material. Several tens of specimens, 6 of them photographed.

Holotype. Fig. 9a , coll. MGP-PD, stub PD120 -OZ836- R08-15 .

Paratype. Fig. 9b , coll. MGP-PD, stub PD120 - OZ839- R02-13 .

Dimensions. Total length of shell 100-114 μm, of abdomen 58-77 μm, diameter of abdomen 77-87.5 μm.

Etymology. From the Latin sardous, – a, - um = Sardini- an.

Remarks. This new species differs significantly from the other species so far described, but shares some characters from other Upper Jurassic species as for instance: its abdominal costae resemble partly those of E. ptyctum (Riedel and Sanfilippo, 1974) from which they differ in being usually present only on the proximal part, and its thorax has costae somewhat similar to those of the thorax of E. pyramis (Aita, 1986) , from which they differ in being more delicate and denser. These characters would suggest that E. sardoum n. sp. originates from E. pyramis , the upper Tithonian and youngest species so far as known and the only one that has costate thorax and abdomen, and a conical cephalis. What we don’t know yet is the time of transition between these two species.

Range and occurrence. Late Valanginian so far as known but, since the last species of the genus was recorded in the latest Tithonian, its FAD should be in Berriasian.

Figures

Fig. 9 a, b - Eucyrtidiellum sardoum Dumitrică n. sp.: a, a1 - holotype, OZ836; b - paratype, OZ839. c-e, g - Hemicryptocapsa capita Tan: c - OZ838, d - OZ824, e - OZ837, g - OZ839. f-f2 - Gongylothorax oculoporus Dumitrică n. sp.: OZ824 and OZ826. h – Gongylothorax (?) sp., OZ834. i-i2 – Gongylothorax verbeeki (Tan), OZ824; i1, i2 - details of apical and apertural parts. j, j1, j2 - Williriedellum buekkense (Kozur), OZ824: j – lateral view, j1 – apical view with sutural pore, jb – distal view. k – Arcanicapsa simplicissima Dumitrică n. sp., OZ836, k1 – distal view showing the apical rosette. l-o, t, t1, u - Kozurium hindei (Tan): l, l1 - OZ837, m - OZ839, n - OZ834, o - OZ836, t-t1 x300, OZ825, n1 – distal aperture of fig. 9n. p-s1 - Cryptamphorella alieviana Dumitrică n. sp.: p, s - OZ825, r - OZ837, s1 detail of test of fig. s. Figs. p-s x200; figs. c-e, g x250; figs. a, a1, b, f, f2, h, h1, i, k-o, t, t1, x300; i1, i2, m 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).