Melanopsis, Ferussac, 1807

Thivaiou, Danae, Harzhauser, Mathias & Koskeridou, Efterpi, 2019, Early Miocene Gastropods from the Felli Section (Proto-Mediterranean Sea NW Greece), Geodiversitas 41 (8), pp. 323-366 : 332-334

Melanopsis sp.

(Fig. 3 F1-F3)

MATERIAL EXAMINED. — Sample F2: AMPG ( IV) 2269-2275 (seven specimens); sample F7: AMPG ( IV) 2276-2279 (four specimens) ; sample F10: AMPG ( IV) 2280 (one specimen).

DIMENSIONS. — Maximum height: 18.0 mm (incomplete).

DISTRIBUTION. — Early Miocene. Proto-Mediterranean Sea: Greece (this paper).

DESCRIPTION

Elongated fusiform shell with acute apical angle and completely flat whorls. Indistinct sutures; shoulder may be present in some specimens. Aperture ovate elongated with slightly elongated siphonal canal; outer lip not preserved; distinct callus. Very weak sculpture consisting of thin sigmoidal growth lines. Residual colour pattern poorly preserved consisting of thin sigmoidal axial lines of approximately equal width.

REMARKS

A single species of Melanopsis was found in Felli, including a broken juvenile specimen. The specimens seem to represent an undescribed species, but the available material is not sufficient to formally describe it. All specimens are broken and the apical part is always missing. This species might already have been discussed from other Oligocene and lower Miocene sections in the Mesohellenic Basin as Melanopsis impressa Kraus, 1852 by Harzhauser (2004) and Harzhauser & Kowalke (2001). Due to the poor preservation of these specimens a comparison with the specimens from Felli remains difficult. In any case, it is unlikely that the Greek records represent Melanopsis impressa , which is a species from the early Miocene of southern Germany (see also discussion in Harzhauser et al. 2016) on Melanopsis hantkeni Hofmann, 1870). A separation of the species from Felli from Melanopsis hantkeni as described by Harzhauser et al. (2016) from the Rupelian of the Thrace Basin is based on its colour pattern of blotches forming a vague zig-zag pattern.

Oligocene and early Miocene Melanopsis species are frequently found in brackish deposits but are assumed to have favoured freshwater envieronments ( Neubauer et al. 2016). In the Serravallian of Turkey, it is still found in brackish deposits ( Landau et al. 2013). In the Pliocene and the Lower Pleistocene of Greece, it is found in brackish deposits with freshwater input (Georgiades-Dikaioulia et al. 2002; Moissette et al. 2016). Here, the presence of Melanopsis is considered to be an indicator of freshwater influx, which is in agreement with the preservation of the specimens.

Figures

FIG. 3. — A1-A4, Paroxystele orientale (Cossmann & Peyrot, 1917), AMPG(IV) 1506; B1-B3, Homalopoma acaste n. sp., holotype, AMPG(IV) 1512; C1, C2, Vitta picta (Férussac,1823),AMPG(IV) 1517; C3, AMPG(IV) 1543 (SEM image);C4, AMPG(IV) 1544 protoconch (SEM image); D1-D4, Neritilia neritinoides (Cossmann & Peyrot, 1917); D1, AMPG(IV) 1517; D2, AMPG(IV) 1541 (SEM image); D3, D4, AMPG(IV) 1541 protoconch close-ups; E1, E2, Plesiotrochus fallax (juv.) (Grateloup, 1832), AMPG(IV) 1605; F1-F3, Melanopsis sp., AMPG(IV) 2276. Scale bars: A, C1, C2, E2, 1 mm; B, 2 mm; C3, D3, 100 µm; C4, D1, E1, F, 500 µm; D2, 200 µm; D4, 50 µm.