Paracoskinolina Moullade, 1965

SCHLAGINTWEIT, FELIX, 2021, Agglutinated Conical Foraminifera (Orbitolinidae, Coskinolinidae) From The Upper Cretaceous (Campanian) Of Greece, With Description Of Paracoskinolina Klokovaensis N. Sp., Acta Palaeontologica Romaniae 17 (2), pp. 83-94 : 89

Genus Paracoskinolina Moullade, 1965

Type species: Coskinolina sunnilandensis Maync, 1950 Paracoskinolina klokovaensis n. sp.

Figs. 3 pars, 5a-j, 6a

1970 Dictyoconus sp. – Fleury, p. 37, pl. 1, figs. 2-3.

Origin of the name: Referring to the type-locality of the new species: Mount Klokova in western Greece.

Holotype: Subaxial section shown in Fig. 5a .

Paratypes: Specimens illustrated in Fig. 5 b-j.

Horizon and locality: late early-middle Campanian of Mount Klokova, SW Greece.

Description: Medium- to high-conical test displaying smooth surface and plane to slightly convex base. The test height may slightly exceed the diameter, often the latter accounts for about 2/3 of the former. A small initial spire is barely visible ( Fig. 5a, i ); the embryo has not been observed. Each adult rectilinear chamber (up to 16 in adult specimens) is subdivided into a marginal and central zone. The exoskeleton of the marginal zone consists of one horizontal partition (rafter) (e.g. Fig. 5b ) and 1 to 2 intercalary beams between the vertical main partitions (beams). The latter are straight and slightly but continuously widening inwards and exceed the length of the intercalary beams distinctly (about 4 times). The pillars of the central zone are aligned between subsequent chambers as visible in axial sections ( Fig. 5b ). In oblique section, they appear slightly offset against each other ( Fig. 5e ). The pillars are widened at the base and top and may have a string-of-pearls appearance ( Fig. 5a ). There are ~5 pillars in axial section for a test diameter of 0.5 mm. The foramina of the central zone are, like the pillars, aligned; the outermost foramina (towards the marginal zone) are arranged in a circle ( Fig. 5d , left side). The wall is finely agglutinated.

Dimensions (in mm):

Test diameter: 0.85-1.1 mm

Test height: 0.75-1.2 mm

Number of chambers per last 0.5 mm cone axis: 6-7 Apical angle: ~28 to 55 degrees

Remarks: From the upper Albian-Cenomanian shallow-water carbonates of the Argolis Peninsula of Greece, Decrouez and Moullade (1974) described four new Orbitolinidae , which amongst them Paracoskinolina fleuryi . This taxon does not possess aligned pillars, instead alternating main partitions, and is therefore excluded from the genus Paracoskinolina Moullade (see emended genus diagnosis of Arnaud-Vanneau, 1980). Although nothing is known about the embryo and the internal structure displayed in transverse sections, this taxon lacks horizontal partitions and has been tentatively transferred to Cribellopsis Arnaud-Vanneau by Yazdi-Moghadam and Schlagintweit (2021). The form described as Dictyoconus walnutensis (Carsey) subspecies pyrenaicus by Moullade and Peybernès (1975) from the lower–middle Albian of northern Spain is similar to the Campanian species from Greece to some extent (e.g. dimensions, one rafter). Schroeder (1985) clarified that this Spanish taxon does not belong to Dictyoconus Blanckenhorn because of the aligned pillars in the former. In addition, Schroeder (1985, p. 46) concluded that “ Dictyoconus ” pyrenaicus should be transferred to Paracoskinolina or an allied form due to the aligned pillars and foramina. In fact, the transverse section provided by Moullade and Peybernès (1975, pl. 1, fig. 1) nicely shows the concentric arrangement of the foramina, a diagnostic feature of the Dictyorbitolininae sensu Schroeder in Schroeder et al. (1990). Some morphological differences, such as a more inflated test and differing apical angle (50-70 degrees, acc. to Schroeder, 1985), of Paracoskinolina pyrenaicus (Moullade and Peybernès) comb. nov. are worth mentioning.

Comparisons: The new species has been described and illustrated by Fleury (1970) as Dictyoconus sp. Contrasting with Paracoskinolina Moullade , Dictyoconus Blanckenhorn has pillars in the central zone that alternate in position between subsequent chambers (e.g., Davies, 1930, 1939; Arnaud-Vanneau, 1980; Loeblich and Tappan, 1987). Having a single rafter in the chamber marginal zone, P. klokovaensis can be compared with P. arcuata Arnaud-Vanneau, 1976 and P. reicheli ( Guillaume, 1956) ( Fig. 6 ). P. arcuata is morphologically different with its cylindro-conical test also displaying larger dimensions (e.g., height> 3 mm) ( Arnaud-Vanneau, 1976, 1980). P. reicheli (Guillaume) is slightly larger as P. klokovaensis and with up to four intercalary beams (e.g. Guillaume, 1956, pl. 1, fig. 6), its marginal zone is more complex. The other species, P. maynci ( Chevalier, 1961) , P. sunnilandensis (Maync, 1950) , and P. coogani Scott, 2002 lack rafters in the marginal zone. Note that many other “ Paracoskinolina ” have already been taxonomically revised or are still in need of revision (e.g., Cherchi and Schroeder, 1982; Schlagintweit, 2020; Yazdi-Moghadam, 2021). These include those described before the taxonomic clarification of the genus provided by Arnaud-Vanneau (1980).

Biostratigraphy: The levels with “Orbitolinidés K” (for Klokova) have been placed into the upper Santonian- Lower Campanian ( Fleury, 1980, fig. 8, p. 44). Fleury (1980) respectively established a zone “Cs B 5 à “Orbitolinidés K” et Montcharmontia apenninica s.s.” In some sections, these orbitolinids appear some metres above the LAD of Murgella lata Luperto Sinni and Keramosphaera tergestina (Stache) ( Fleury, 1980, figs. 18 and 30) while in others (including the material studied herein) M. lata and the first Orbitolinids display overlapping ranges (op. cit., Fig. 25). Lepinoconus chiocchini was reported within a rather short interval at its type-locality in southern Italy, “bracketed between the K. tergestina level….and the upper limit of the S. mediterranea subzone”, that is lower Campanian. With this data, the Orbitolinid levels of Klokova Mountain can be assigned to the uppermost lower-middle Campanian (see Fig. 15 in Frijia et al., 2015: SIS data; Cruz-Abad et al., 2017; Villalonga et al., 2019).

Figures

Fig. 3 Upper Cretaceous (middle Campanian) microfacies of sample GKL 39. Pa = Paracoskinolina klokovaensis n. sp., Pal = Paleodictyoconus senonicus Moullade & Viallard, Di = Dicyclina schlumbergeri Munier-Chalmas.

Fig. 5 Paracoskinolina klokovaensis n. sp., from the late early-middle Campanian of Mount Klokova, SW Greece (a-f, h-j) and Brač Island, Croatia (g). a Axial section. b-c, f-g Subaxial sections. d Oblique transverse section. h Oblique section. i Tangential section. j Axial section, holotype specimen. Abbreviations: b = beam, f = foramen, ib = intercalary beam, pi = pillar, r = rafter. Thin sections: a GKL 39 (1754) (from Fleury, 1970, pl. 1, fig. 2), b-j GKL 39 (3357).

Fig. 6 Comparison of Paracoskinolina species with one horizontal partition in the marginal zone: a P. klokovaensis sp. nov., b P. reicheli Guillaume, 1956. c P. arcuata (Arnaud-Vanneau 1976). D = test diameter, H = test height, n = number of chambers per last 0.5 mm axial length, h = chamber height (all data except D/H in mm). * measured from original illustrations. Stratigraphy of the two Lower Cretaceous species according to Clavel et al. (2014).