Turbonilla s.l. sp. 1, Risso, 1826

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 : 356

Turbonilla s.l. sp. 1

(Fig. 9 A1-A3)

MATERIAL EXAMINED. — Sample F11: AMPG ( IV) 2580-2582 (three specimens).

DIMENSIONS. — Maximum height: 2.15 mm (incomplete), diameter: 0.65 mm.

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

DESCRIPTION

Type A2 helicoidal protoconch forming an angle of 115° with the axis of the shell; diameter: 195 µm. Largest available fragmentary specimen consisting of six flat teleoconch whorls forming moderately slender shell of c. 22°; sculpture consisting of opisthocline convex equally-spaced ribs numbering 6 on last preserved whorl, separated by concave interspaces of roughly same width. Axial ribs terminating as distinct tips at adapical suture (not fading out) and passing into weak spiral cord at transition into base on last preserved whorl. No spiral sculpture. Sutures linear and impressed; no columellar fold; aperture missing.

REMARKS

The present species shares many morphological similarities with Turbonilla spiculoides Cossmann & Peyrot, 1917 from the Early Miocene of France (Aquitaine) as far as the sculpture is concerned. The protoconch is very similar in terms of size for the Greek species and T. spiculoides. The main difference is that T. spiculoides has more rounded ribs and the space between the ribs is shallower. Moreover, its teleoconch whorls are slightly convex ( Cossmann & Peyrot 1917; Lozouet et al. 2001). Other similar species are T. gastaldi (Semper, 1865) and T. superstructa Boettger, 1907, which present similar sculptures but can be less slender and have more convex whorls.

Figures

FIG. 9. — A1-A3, Turbonilla (s.l.) sp. 1, AMPG(IV) 2580; B1-B3, Turbonilla (s.l.) sp. 2, AMPG(IV) 2583; C1, C2, Turbonilla (s.l.) sp. 3, AMPG(IV) 2584; D1-D3, Turbonilla (s.l.) sp. 4: D1, AMPG(IV) 2586 (SEM image); D2, D3, AMPG(IV) 2687. Scale bars: 500 µm.