Hypanis plicata ( Eichwald, 1829 )

van de Velde, Sabrina, Yanina, Tamara A., Neubauer, Thomas A. & Wesselingh, Frank P., 2020, The Late Pleistocene mollusk fauna of Selitrennoye (Astrakhan province, Russia): A natural baseline for endemic Caspian Sea faunas, Journal of Great Lakes Research 46 (5), pp. 1227-1239 : 1235

Hypanis plicata ( Eichwald, 1829)

( Fig. 4 : 5).

*1829 G. [lycymeris] plicata Eichwald : 279, pl. 5, fig. 2a–d.

1986 Adacna (Hypanis) plicata ( Eichwald, 1829) – Yakhimovich et al.: 85, pl. 7, fig. 2.

2013 Hypanis plicata ( Eichwald, 1829) – Bogutskaya et al.: 387, fig. 164, photo 56.

Dimensions – Estimated max. L 19.5 mm, H 14 mm (all larger shells in the sample are broken). Logvinenko and Starobogatov (1969) reported L 35 mm and H 26 mm for this species.

Characterization – Thin-shelled, subquadrangular to subelliptical intermediate convex shell with edentulous hinge; shell flattened; ribs are thin, erect and separated by wide concave interspaces.

Taxonomic notes – In the Northern Caspian, there are sometimes smaller individuals that can resemble somewhat the outline of Adacna vitrea forma glabra, from which they differ by their welldeveloped ribs ( Logvinenko and Starobogatov, 1969).

Ecology – The species occurs on muddy to sandy-muddy lake floors and shelly firm grounds in the north, middle and south CS ( Bogutskaya et al., 2013). Lives down to 30 m water depth in salinities between 4 and 8 psu ( Bogutskaya et al., 2013; Logvinenko and Starobogatov, 1969). However, our own observations of Hypanis washed ashore along coasts of the Middle and South Caspian basins suggest they may have lived in slightly higher salinities as well.

Figures

Fig. 4. Cardiidae. (1) Adacna laeviuscula; (a) RGM.1309812 LV; (b) RGM.1309813 RV. (2) Adacna minima; (A) RGM.1309811 LV; (b) RGM.1309810 RV. (3) Monodacna semipellucida, RGM.1309802 RV; (4) Monodacna caspia s.l. (a) RGM.1309803 LV; (b) RGM.1309804 RV. (5) Hypanis plicata; (a) RGM.1309808 LV (b) RGM.1309809 RV. Scale bars = 1 cm.