Charentia cf. cuvillieri Neumann, 1965

Charentia cf. cuvillieri Neumann, 1965 View in CoL

Fig. 4 View Fig a-j

The synonymy includes the original reference and exclusively Upper Cretaceous (post-Cenomanian) occurrences.

1965 Charentia cuvillieri gen. et sp. nov. – Neumann, p. 93, pl. 2, figs. 6-12 (Cenomanian of France).

1976 Navarella ? sp. – Luperto Sinni, pl. 46, fig. 4 (Upper Cretaceous of S-Italy).

1986 Lituolidae aff. Navarella sp. – Bouyx & Villain, fig. 7k (Upper Cretaceous of Afghanistan).

1992 Lituola ? sp. – Schlagintweit, p. 331, pl. 1, figs. 6-8 (middle Coniacian of Austria).

2009 Charentia cf. cuvillieri Neumann – Villalonga, p. 100, pl. 4, figs. 7, 9 (Campanian of Spain).

2020 Navarella sp. Ciry & Rat – Sha et al., fig. 9c ( Campanian of Western Tibet) .

Remarks: This planispirally coiled agglutinated taxon has already been reported from Coniacian-Campanian strata of different areas and assigned to Charentia Neumann, 1965 but sometimes cautiously also to Navarella Ciry & Rat, 1951 and Lituola Lamarck, 1804 (see synonymy). The type-species Charentia cuvillieri (sensu stricto) has a rather long range from the late Berriasian to Cenomanian ( Bucur et al., 2020; Simmons & Bidgood, 2023). Besides other differences, Charentia possesses some kind of a pseudo-keriothecal wall as evidenced by Loeblich & Tappan (1985a, p. 94, ‘…an inner part with cylindrical pseudoalveoles that do not extend completely to either the inner or outer surface, but are visible and give an almost keriothecal appearance in thin section’), whereas Navarella has a non-perforate agglutinated wall. In both taxa, the well discernible agglutinated grains are often concentrated in the outer part of the wall. In Navarella the inner part is finely agglutinated homogeneous whereas in Charentia one might observe a finely perforate layer. In fact, the pseudokeriothecal appearance of the wall is rarely visible and preserved and is so far unrecorded from the above mentioned Upper Cretaceous (post-Cenomanian) occurrences and illustrations. Here, this structure is reported for the first time from a specimen coming from the early-middle Campanian of Brač island, Croatia (see Gušić & Jelaska, 1990; Cvetko Tešović et al., 2001; Schlagintweit et al., 2023) ( Fig. 4 View Fig h-i). Arnaud-Vanneau (1980, p. 17) argued that this type of wall-structure has only been observed in some large Cenomanian forms but not the smaller Lower Cretaceous forms. Arnaud-Vanneau furthermore concluded that in the case that the pseudo-keriothecal-type wall structure only exists in the Cenomanian specimens it would be necessary to redefine the species respectively defining two different species (‘ nécessaire soit de redefine l’espèce, soit de la scinder en deux ’, p. 18’). In fact, this wall structure is only very rarely unambiguously preserved. Some specimens from the late Barremian-early Aptian of Iran, however, showed this structure making a further taxonomic splitting unnecessary ( Fig. 5 View Fig ).

Concerning the biometric data, striking differences between our specimens and the type-species Ch. cuvillieri are not evident (see Arnaud-Vanneau, 1985). There appear to be a slightly lower number of chambers in the last whorl (9 to 11 cf. 11-13 in C. cuvillieri s.s. acc. to Arnaud-Vanneau, 1985). However, according to own observations, Charentia cuvillieri from the Lower Cretaceous of Iran may have also 8 chambers in the last whorl. This led Villalonga (2009) to ascribe the post-Cenomanian representatives to the type-species with some reservation, a conclusion further substantiated by the new observations on the wall structure. For the pre- Cenomanian specimens, Arnaud-Vanneau (1985) reported two size ranges: small forms with diameters of 0.780 mm and 0.830 mm (up to 1.135 mm in enrolled specimens) and large forms with diameters of 1.210 mm to 1.400 mm (up to 1.610 mm in enrolled specimens). The large forms are said to be restricted to the Cenomanian. We may note that the size of the Chinese specimens is much greater than 1.0 mm (maximum 1.75 mm) corresponding to the ‘ formes de grande taille ’ sensu Arnaud-Vanneau (1985). Also, the measured diameters of the proloculi are larger in the post-Cenomanian specimens ( Table 1). Besides considering the possibility of different species, one might also take into consideration that this may be an example of the macroevolutionary pattern of what is known as Cope’s rule; the increase in size in lineages in time especially when the ‘ risk of lineage extinction is low ’ (e.g., Roy et al., 2024, p. 1).

In conclusion, it appears reasonable to separate the post-Cenomanian forms having a rather wide distribution especially in the Campanian shallow-water carbonates as Ch. cf. cuvillieri following Vilalonga (2009) and pending a thorough morphometric analysis.