Crococapsidae 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 : 129-130

Family Crococapsidae Dumitrică n. fam.

Type genus. Crococapsa O’Dogherty, Goričan and Gawlick, 2017 .

Diagnosis. Conical and distally closed tetracyrtid, exceptionally tricyrtid nassellarians with cephalic cavity divid- ed into two chambers by a transversal septum, and the last chamber without a distal aperture. First three, or two chambers in case of tricyrtid shell, forming a cylindrical or conical body well distinct from the last chamber, which is much larger.

Remarks. This new family is erected for the genera Crococapsa O’Dogherty, Goričan & Gawlick 2016 , Ocellicapsa n. gen. and Squinabolum Dumitrică 1970 , that differ from the members of the family Minocapsidae O’Dogherty, Gorican & Gawlick 2017 by having the cephalis divided into two chambers by a transversal septum rather similar to that of the family Amphipyndacidae or to the genus Squinabollum .

The family Crococapsidae , as defined herein, includes only the cited genera. The genera Doliocapsa O’Dogherty, Goričan & Gawlick, 2017 , Hemicryptocephalis Li 1988 and its related genus, Quarkus Pessagno, Blome & Hull in Pessagno et al. 1993, are excluded from this new family because their cephalis is simple and the last segment has an aperture.

The amphipyndacid structure of the cephalis is very easily visible in the Text-fig. 2, which represents an inner cast of Crococapsa uterculus (Parona, 1890) from a Lower Cretaceous chert of Turkey. It shows also that the abdomen of this species is also partly encased in the postabdominal chamber and, for this reason, the ocelli are opened in apical direction and, consequently, they are better seen in apical or obliquely apical positions (see Fig. 12f 1 ). The two-chambered cephalis was also well illustrated by Tan Sin Hok (1927, pl. 14, figs. 118-120), with drawings of his Lower Cretaceous species Cyrtocapsa asseni Tan and Cyrtocapsa houwi Tan (that should be assigned to the genus Crococapsa ), and probably also of Stichocapsa pseudoornata (Tan, l927, pl. 15, fig. 134). The lower chamber of the cephalis is easily recognizable by its shorter height and narrower diameter compared with the respective size of the upper chamber (see also Foreman, 1966, text-figs. 7-11). Other good images of the two-chambered cephalis are very well visible in Sethocapsa uterculus (Parona) illustrated in transmitted light by Schaaf (1981, pl. 26, figs 5a, b), and also in Siphocampium davidi Schaaf (1981, pl. 27, figs. 10a, b) and Siphocampium rutteni (Tan, 1927, pl. 27, figs. 11a, b). Consequently, S. davidi becomes a species of Crococapsa , and S. rutteni of Ocellicapsa nov. gen. (see below) due to its tuberculate postabdominal segment.

A short mention deserves the genus Siphocampium Haeckel, 1881 , adopted by Schaaf for the species S. davidi and S. rutteni and also for Dicolocapsa macropora Rüst, 1888 ). As Schaaf himself (1981, p. 438) mentioned, he used questionably this genus because its type species ( Siphocampium accrescens Rüst, 1885 figured on pl. 13, fig. 11, from the Upper Jurassic radiolarian cherts of Riggi, Switzerland) “has a cephalis sufficiently elongated to accommodate two chambers, and that this name is used to avoid or postpone the necessity of establishing a new genus”. This type species has a cylindrical cephalis and a scalariform skeleton formed of 4 short cylindrical chambers that increase in diameter very fast, and the last chamber has the distal border frayed suggesting that it represents an apical fragment of an entire specimen. For this reason, O’Dogherty (2009, p. 441, fig. 542), in his inventory of Mesozoic radiolarian species, considered this species a nomen dubium nassellarian. This fragment resembles perfectly the apical part of the upper Middle to lower Upper Jurassic species Palinandromeda podbielensis (Ozvoldova, 1979) and its probable synonym Andromeda violae Baumgartner 1980 , a Bathonian to Oxfordian nassellarian species well illustrated in Baumgartner et al. (1980, 1995). Consequently, we can now consider with sufficient certainty that Siphocampium accrescens Rüst 1885 is nothing else than a proximal fragment of Palinandromeda podbielensis (Ozvoldova 1979) .

Figures

Fig. 12 b - Crococapsa cf. horokanaiensis (Kawabata), OZ834. a, c, d - Crococapsa zweilii (Jud): a, OZ826; c, OZ836; d, OZ825. e-h - Crococapsa uterculus (Parona): e, f, h - OZ834, g - OZ825. i-o - Ocellicapsa ruthae Dumitrică n. sp.: i - OZ837, j - OZ837, k - OZ836, i - OZ834, m - OZ824, n - OZ838, n1 - detail of cephalothoracic body, arrow shows the place of very small pores at the boundary between the two parts of cephalic cavity, o - OZ825. p, r, t, v - Squinabolum elegans Dumitrică n. sp.: p - OZ824, r - OZ826, t - OZ836, s - Amphipyndax zyabrevi Dumitrică n. sp. - OZ825. u - Campanomitra pulchella (Rüst), OZ836. v - OZ834. w, x - Archaeodictyomitra inflata Dumitrică n. sp.: w - OZ839, x - OZ834. Figs. a, c-h, u x250, all the others 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).