Corymbina elegans (Cantraine, 1841)

Neubauer, Thomas A. & Wesselingh, Frank P., 2023, The Early Pleistocene freshwater mollusks of the Denizli Basin (Turkey): a new long-lived lake fauna at the crossroads of Pontocaspian and Aegean-Anatolian realms, Zitteliana 97, pp. 53-88 : 53

Corymbina elegans (Cantraine, 1841)

Fig. 16A-C

*1841 Ad. Corymbina [ Corymbina elina ] Corymbina elegans . Nob. - Cantraine: 156, pl. 5, fig. 12, 12a.

1847 Limneus Adelina - Spratt and Forbes: 177, textfig. a.

? 1877 Lymnaeus Adelinae [sic] Forbes [sic] - Fuchs: 5, pl. 1, fig. 4.

? 1877 Lymnaeus Adelinae [sic] Cantr. - Fuchs: 37, pl. 4, figs 1-6.

1923 Radix (Adelinella) elegans (Cantraine) - Wenz: 1319-1320.

1973 Radix (Adelinella) elegans (Cantraine) - Schütt and Besenecker: 16, pl. 1, figs 19, 20.

1981 Corymbina elegans (Cantraine) - Willmann: pl. 13, figs 18-20.

? 2022 Corymbina elegans (Cantraine, 1841) - Neubauer: fig. 6.7k, l.

Material.

1 juvenile specimen (RGM 962696) from sample 2.

Type locality.

Italy; no further details known-Cantraine wrote: "Je ne connais cette espèce qu’à l’état fossile, le seul individu que je possède m’a été donnée par mon ami M. Rossi de Livourne, qui a’en connaissait pas exactement la provenarco." [I only know this species in the fossil state, the only individual I have was given to me by my friend Mr. Rossi from Livorno, who didn’t know exactly where it came from.].

Description.

Shell comprises protoconch and about 0.75 teleoconch whorls. Initial part of protoconch smooth, followed by quarter whorl bearing faint riblets. P/T boundary not clearly visible, but probably coincides with weak angulation and onset of growth lines. Soon distinct, sharp ribs develop, which soon become broader and bulgier, leading to an irregular, wavy surface. Aperture fragmented, parts of outer lip missing; originally apparently elliptical. Umbilicus narrow.

Remarks.

Spratt and Forbes (1847) mentioned the name Limneus [sic] Lymnaea adelina along with an illustration, making the name available. However, they clearly referred it to be the same species as Adelina Prososthenia elegans Cantraine, 1841, rendering Lymnaea adelina a junior objective synonym of Corymbina elegans . The specimen they illustrated has a much larger aperture, but the species has an extremely variable shell (see also Willmann 1981).

Corymbina bicarinata (Fuchs, 1877) from the Early Pleistocene of Livanates (Phthiotis, Greece) has a Radix -like appearance, with broad ovoid, attached aperture, an angulated last whorl, slender ribs, and small, pointy spire (Neubauer 2023b). Specimens from the same deposits identified by Fuchs (1877) as L. adelinae [= C. elegans ] differ considerably from the phenotypes shown by Cantraine (1841), Spratt and Forbes (1847), and Willmann (1981). They rather resemble C. bicarinata , yet with a keel at the angulation. More data on the variability of both species is needed to disentangle their taxonomy and synonymies. We tentatively associate our single juvenile specimen with C. elegans given the general match in shell shape and sculpture as well as the known stratigraphic and geographic distribution of the species.

The Late Miocene Corymbina rhodensis Bukowski, 1892 is smaller and has a more slender shell, often with reduced sculpture ( Willmann 1981). In both C. elegans and C. rhodensis specimens occur with the last whorl partly or entirely uncoiled ( Willmann 1981). Corymbina aegaea (Oppenheim, 1919) from Upper Miocene (?) deposits near Harmancık (NW Turkey) has a more elongated shell ( Schütt and Kavusan 1984). The Early Sarmatian (Serravallian, Middle Miocene) Corymbina coronata (Marinescu, 1992) from Romania differs from C. elegans in the more angulated body whorl and the ribs being reduced to elongated knobs at the uppermost whorl portion.

Corymbina rhodensis senestris İnal, 1975 from supposedly Pliocene sediments at Gürleyik SE Afyonkarahisar (c. 170 km ENE Denizli) shows a similar type of sculpture, but it is a rare case of a sinistral representative ( İnal 1975). It is questionable, however, if it represents a distinct species or simply an aberrant morphotype of an existing species.

Distribution.

Corymbina elegans has been reported from the Pliocene of the Denizli, Eşen, and Çameli basins in Turkey ( Spratt and Forbes 1847; Oppenheim 1919; Wenz 1923), the Early Pliocene of central Italy ( Esu and Girotti 2018), and the Pliocene-Pleistocene of Greece (Wenz 1923; Schütt and Besenecker 1973; Gillet et al. 1979). Records from the Late Miocene (Chios Island; Schütt and Besenecker 1973) are probably based on an outdated stratigraphy.

Figures

Figure 16. Lymnaeidae of the Kolankaya I fauna. A-C. Corymbina elegans (Cantraine, 1841), RGM 962696, sample 2. D-F. Radix sp., RGM 1310798, sample 2. Scale bars: 1 mm.