Cyclolina cretacea d’Orbigny, 1846

Cyclolina cretacea d’Orbigny, 1846 View in CoL

Figure 13 View Fig

T 1846 Cyclolina cretacea n. sp. – d'Orbigny, p.139; pl. 21, fig. 22-25; Turonian (now regarded as middle Cenomanian – Moreau, 1976), western France.

1919 Cyclolina cretacea – Douvillé, p. 1131; text-fig. 2; Cenomanian, western France.

1949 Cyclolina cretacea – Cuvillier & Szakall, p. 11; pl. 2, fig. 15; pl. 13, fig. 11; Cenomanian, western France.

1964 Cyclolina cretacea – Loeblich & Tappan, p. C301- C302; text-fig. 207 (1a-b); middle Cenomanian, western France.

1964 Cyclolina cretacea – Neumann, p. 49-52; pl. 1, fig. 1-4; text-fig. 1; Cenomanian, western France.

1967 Cyclolina cretacea – Neumann, p. 128-132; pl. 15, fig. 1-3; text-fig. 78-79; Cenomanian, western France.

? 1978 Cyclolina cf. cretacea – Berthou & Schroeder, pl. 9, fig. 2; latest Albian, Portugal.

1985 Cyclolina cretacea – Cherchi in Schoeder & Neumann, p. 18-19, pl. 4, figs. 1-11; middle Cenomanian, western France.

1987 Cyclolina cretacea – Loeblich & Tappan, p. 94, pl. 86, figs. 1-8; middle Cenomanian, western France.

Non 2011 Cyclolina aff. cretacea – Boix et al., p. 816, fig. 10a-d; Coniacian, Spanish Pyrenees [most likely a new species].

Reference Images: Schroeder & Neumann (1985) pl. 4, figs. 1-11.

Taxonomy/Identity: This species was comprehensively reviewed by Cherchi in Schroeder & Neumann (1985). No further taxonomic study has been carried out since then.

The genus Cyclolina was introduced by d’Orbigny (1846), with the species Cyclolina cretacea its type by monotypy. It is a simple, large (up to 6.7 mm) discoidal, microgranular/finely agglutinating form, increasing in thickness towards the periphery. Adult chambers are cyclic, with concentric sutures slightly depressed, and a simple interior with no internal partitions. A multiple aperture of rounded pores is scattered in many rows over the apertural face. Three ontogenetic stages are recognised: (i) a central embryonic apparatus consisting of a protoconch and a deuteroconch. The maximum inner diameter of the protoconch varies between 0.08 and 0.1 mm. In equatorial section, the deuteroconch is crescentshaped; its diameter varies between 0.1 and 0.12 mm; (ii) the embryonic apparatus is followed by a rectilinear series of 4-5 undivided sickle-shaped chambers; (iii) 40- 55 undivided annular chambers, of which the height and thickness increase during ontogeny (description after Cherchi in Schroeder & Neumann, 1985; Loeblich & Tappan, 1987).

Confusion with the soritid genera Broeckina Munier-Chalmas, 1882 and Pastrikella Cherchi, Radoičić & Schroeder, 1976 is possible in random sections, although suggestions that some illustrations of C. cretacea from western France ( Neumann, 1964, 1967) are of these genera (Cherchi et al., 1976) is rejected ( Saint-Marc, 1977; Cherchi in Schroeder & Neumann, 1985). It may also be confused with Balkhania Mamontova / Neobalkhania Cherchi, Radoičić & Schroeder , where the subepidermal network is often not well discernible.

Confident Stratigraphic Range: middle Cenomanian.

Uncertain Stratigraphic Range: latest Albian and early and late Cenomanian.

The only reliable illustrated records of this species are those pertaining to the type and nearby localities in western France as illustrated and documented by Cherchi in Schoeder & Neumann (1985). These are middle Cenomanian, and Schroeder & Neumann (1985) thus restricted the range of the species to the middle Cenomanian. Saint-Marc (1966) mentioned the species (not illustrated) from Landes in western France in association with Praealveolina tenuis , thus undifferentiated middle – late Cenomanian. Calonge et al. (2002) reported (not illustrated) the species from Spain in association with Praealveolina iberica , thus possibly early Cenomanian. It was reported (not illustrated) from Albian/Cenomanian transition beds of Portugal (Berthou, 1973; Berthou & Lauverjat, 1979) but restricted to the latest Albian by Berthou & Schroeder (1978) who illustrated an uncertain “cf.” form. A report from the late Cenomanian –?early Turonian of Kuwait (El-Naggar & Al-Rifaiy, 1973) is not supported by a convincing illustration.

Boix et al. (2011) illustrated an "aff." form, probably a new species (larger than C. cretacea from the type locality), from the Coniacian – Santonian of Spain. One of us (LC) has observed similar forms in the similar aged Ilam Formation of the Iranian Zagros. Very small forms (up to an equatorial diameter of 1.10 mm) of Cyclolina sp. were found by Taslı & Solak (2019) in the late Albian of the Turkish Taurides.

Geographic Distribution: Confirmed occurrences are restricted to France but this species has been reported (though unconfirmed) more widely. It was reported, but not illustrated from Croatia (Sakač, 1970; Magas et al., 1999), Greece ( Zambetakis-Lekkas et al., 1995) and the Iranian Zagros (e.g., Omidvar et al., 2014a, b; Rikhtegarzadeh et al., 2016; Asghari et al., 2022).