Cryptamphorella circumthoracica 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 : 123

Cryptamphorella circumthoracica Dumitrică n. sp.

Figs. 6i ; 10 g, g 1

1988 Cryptamphorella sp. B – Thurow, p. 401, pl. 8, fig. 22.

1989 Cryptamphorella sp. – Matsuoka, fig. 2.11.

1991 radiolari – Dieni & Massari, fig. 23i = Fig. 6i in the present article.

2009 Cryptamphorella clivosa (Aliev) – Ishii et al., p. 348, pl. 21, fig. 20.

2009 Cryptamphorella conara (Foreman) – Ishii et al., p. 348, pl. 21, fig. 21.

Description. Abdomen large, spherical, with small pores arranged quincuncially on most part of its surface and slightly polygonally framed externally. Distal part closed. Cephalothorax with cephalis exposed outside with only its apical half and bearing very small sparse pores, and thorax bell-shaped and enclosed in the abdominal cavity. Cephalothorax situated in a slightly depressed circular area bordered by a circular ridge. Sutural pore open on the trajectory of this ridge. Its margin is thick and it is closed on the inner side by a sieve plate with small pores representing a portion of the thoracic wall. Pores of abdomen very small and usually regularly arranged.

Studied material. A single specimen in sample OZ838, and others from the Masirah Island ( Oman), and Murguceva Formation, Svinița ( Romania).

Holotype. The illustrated specimen, coll. MGP-PD, stub PD120 -OZ838- R05-15 , 15 a.

Dimensions. Diameter of abdominal shell 198 µm, of collar 90 µm.

Etymology. From the Latin circum = around and thorax = thorax.

Remarks. The species is very characteristic by bearing a circular ring on the abdomen around the cephalothoracic structure and on the level of the sutural pore, and a large abdomen with hexagonally framed small pores. The specimen illustrated by Thurow (1988, see synonymy) from the upper Hauterivian-lower Aptian is surely conspecific with the holotype. A similar specimen was found but not published in the Valanginian of the Svinița section, Murguceva Formation, Romania (see Dumitrică, 1995, for the section). The specimens illustrated by Ishii et al. (2009, see synonymy) seem also to be close to this new species although the peri-cephalothorax circular ring is not too much pronounced. The specimen illustrated by Matsuoka ( 1989) as Cryptamphorella sp. could represent this taxon because it has a sutural pore with protruding rim similar to that of the holotype, but the perithoracic circumferential crest is not too well marked.

Range and occurrence. Very rare in sample OZ838, in the Valanginian of Svinița ( Romania), in the upper Valanginian-Hauterivian of Maghilah Unit, Masirah Island ( Oman), and in the Barremian of Fayah Unit (Masirah Island).

Figures

Fig. 6 Radiolarians illustrated by Dieni & Massari, 1991 in their Fig. 23c-i which correspond to the letters from that article: c - Favosyringium affine (Rüst), d - Pseudoxitus seriola - Dumitrică, e - Williriedellum peterschmittae Schaaf, f - Cryptamphorella Dumitricăi Schaaf, g – Ristola nakatonbetsensis Tumanda, h - Crococapsa zweili (Jud), i - Cryptamphorella circumthoracica Dumitrică n. sp., Fig. c x200, figs. d-i x250.

Fig. 10 a-c1 - Hemicryptocapsa (?) bellireticulum (Wu & Li): a - OZ825, b - OZ836. c - OZ838, c1 - OZ824. d-f, j-j2 - Williriedellum labeosum Dumitrică n. sp.: d, e, j-j2, OZ837, f - OZ834. g, g1 - Cryptamphorella circumthoracica Dumitrică n. sp., OZ838; g1 - view of apical part. h, k-o – Cryptamphorella dumitricai Schaaf: h - detail of sutural pore, k - OZ825, l - OZ 824, m - OZ838, n-o, OZ839. i, i1- Williriedellum gilkei Dumitrică, OZ838. p - Zhamoidellum ovum Dumitrică, OZ839. r - Williriedellum cordiforme Dumitrică n. sp., OZ837. s, s1 - Williriedellum occultithorax Dumitrică n. sp. in lateral and obliquely apical views, OZ826. t-t2 – Cryptamphorella crassilabrosa Dumitrică n. sp., OZ837: t, t1 - holotype in two positions, t2 – sutural pore much magnified showing inside the wall of the hidden thorax. Figs. a-f, i, h, k-o, r x250; g, gi, h, t, t1 x300.

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).