Smaragdia merignacensis ( Cossmann & Peyrot, 1917 )

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 : 330

Smaragdia merignacensis ( Cossmann & Peyrot, 1917)

Neritina (Smaragdia) merignacensis Cossmann & Peyrot, 1917: 58 , pl. 8, figs 21-24.

MATERIAL EXAMINED. — Sample F10: AMPG ( IV) 1596-1599 (four specimens [one juvenile]); sample F11: AMPG ( IV) 1600, 1601 (two specimens).

DIMENSIONS. — Maximum diameter: 3 mm (incomplete); maximum height: 2.85 mm (incomplete).

DISTRIBUTION. — Early Miocene. Aquitanian. NE Atlantic: France ( Cossmann & Peyrot 1917; Lozouet & Londeix 2014a [supplementary material CD-Rom]); Proto-Mediterranean Sea: Greece (this paper); Burdigalian. NE Atlantic: France ( Cossmann & Peyrot 1917).

DESCRIPTION

Shell small, convex, with weakly incised suture; aperture wide; columellar area smooth in juveniles and with small denticles in adult shells. Sculpture consists only of inconspicuous growth lines. Colour pattern consists of wavy opisthocline lines interrupted by two white spiral bands.

REMARKS

The specimens from Felli seem to be conspecific with S. merignacensis with which it agrees in colour pattern and morphology. The colour pattern is somewhat variable ranging from thinner to broader axial lines of the same shape. Juveniles have a relatively simpler pattern with lines that appear at the adapical suture that are always thinner than in adult ones. This species was reported by Cossmann & Peyrot (1917) from the Aquitanian and Burdigalian of the Aquitaine Basin ( France), and although it is not reported from other European locations, the description and illustration fit with the specimens described herein. The largest specimens of the present material are incomplete, but largest fragments suggest a similar size to the French specimens (about 6 mm maximum height).

Smaragdia species are extremely scarce in Miocene fossiliferous localities throughout Europe. Smaragdia expansa (Reuss in Hörnes, 1856) , from the middle Miocene of the Paratethys and north-eastern Atlantic, differs in having a much larger aperture, finer denticles on the columellar area and a more shouldered last whorl.

Recent Smaragdia species have been reported to feed selectively on seagrass tissue ( Rueda & Salas 2007) and they are always associated with seagrasses ( Zuschin et al. 2009; Reich et al. 2014). Therefore, the presence of Smaragdia in Felli suggests the presence of seagrass environments.

Subclass CAENOGASTROPODA Cox, 1960 Superfamily CAMPANILOIDEA Douvillé, 1904 Family PLESIOTROCHIDAE Houbrick, 1990