Gongylothorax oculoporus 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 : 114-116

Gongylothorax oculoporus Dumitrică n. sp.

Figs. 9 f-f2

1981? Gongylothorax verbeeki (Tan Sin Hok) – Schaaf, p. 434, pl. 1, figs. 1a, b; pl. 9, figs. 9a, b.

Description. Shell dicyrtid, small and globular with a small cephalis partly sunk in the thorax so that what one can see is its rounded apical part. Thorax globular with a small circular distal aperture (fig. f2). No sutural pore could be seen, so that we do not know whether it is missing or, most probably, situated on the opposite side. Pores very small with double layers ( Fig. f1 ): an inner layer with very small circular pores and an outer layer with larger cylindrical diameter. Pores arranged in curved rows. Surface rather smooth as the polygonal interporal frames are not sharp.

Studied material. Two specimens, one in OZ824 and one in OZ826.

Holotype. Figs. 9f, f 1 , sample OZ824, coll. MGP-PD, stub PD120 -OZ824- R13-35 .

Paratype. Fig. 9f 2 , sample OZ826, coll. MGP-PD, stub PD120 - OZ826- R11-13 .

Dimensions. Length of shell 100-106 µm, of thorax 90 µm, diameter of thorax 88-90 µm.

Etymology. From the Latin oculus - eye and porus - pore, because, at high magnification (fig. 9f1), its pores resemble eyes with pupils in the centre.

Remarks. This species differs from G. verbeeki (Tan) by having pores with two diameters: very small diameter on the inner side of the wall and larger cylindrical opening on the outer side, and the passage between two diameters is abrupt, as if the wall consists of two layers.

Occurrence. Found only in the two cited samples.

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).

Fig. 2 Geological section across the S’Ozzastru area (trace A-A’ in the geological map of Fig. 1). Legend: a - Recent and present alluvial deposits (Holocene). b - Cuccuru ’e Flores Conglomerate: sandstone and breccia (middle Eocene). c - Siniscola Marl: marl (1) and marly limestone (2) (late Valanginian). d - Schiriddè Limestone: cherty limestone (early Valanginian). e - Monte Bardia Limestone: limestone (early Tithonian - late Berriasian). f - S’Adde Limestone: limestone and cherty limestone (latest Bathonian - earliest Tithonian). g - Dorgali Formation: dolostone (middle-late Bathonian). h - Metamorphic basement (Palaeozoic). i - Fault (modified from Bottini et al., 2018).