‘ Odostomia ’ s.l. sp. 1, J. Fleming, 1813

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 : 350

‘ Odostomia ’ s.l. sp. 1

(Fig. 7 H1-H4)

MATERIAL EXAMINED. — Sample F11: AMPG ( IV) 2557 (one specimen).

DIMENSIONS. — Maximum height: 1.75 mm.

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

DESCRIPTION

Type C partially immersed tilted protoconch. Teleoconch whorls shouldered, smooth and flat, sutures deeply incised, V-shaped. Sculpture on the base of the shell consists of fine spiral grooves and axial growth lines. Last whorl slightly angular; aperture rhomboid; umbilicus very restricted; columellar tooth moderately developed.

REMARKS

The present species is easily set apart from other Odostomiinae by having a conical shape, a relatively solid shell with flat whorls and very distinct sutures. The partially immersed protoconch forms an acute angle with the first teleoconch whorl of about 45°. The almost indistinguishable subsutural collar gives a shouldered aspect to the whorls and accentuates the sutures.

Morphologically, it is most similar, regarding the shape of the whorls, the protoconch and the aperture, to the recent species Odostomia didyma (Verrill & Bush, 1900) (= Eulimastoma didymum (Verrill & Bush, 1900)?). Nevertheless, the genus Eulimastoma Bartsch, 1916 is characterised by spiral microstructure which is not observed on the present specimen, possibly due to the preservation of the shell.

Furthermore, the shape and overall morphology of Odostomia (Pyramistomia) fehrae van Aartsen, Gittenberger & Goud, 1998 is similar. The latter species is classified in Pyramistomia Cossmann, 1921 at the subgenus level, on grounds of having similarities with Odostomia deubeli Boettger, 1901 (= Pyramistomia deubeli Boettger, 1901) (type species of Pyramistomia) (van Aartsen et al. 1998). In a revision of the genus Eulimastoma Bartsch, 1916 , Pimenta & Absalão (2004) mention that O. (Pyramistomia) fehrae is related. In the present state of knowledge of the apomorphies of these genera, it is not possible to assign the present specimen with certainty, thus its placement in Odostomia s.l.

Figures

FIG. 7. — A1-A3, Mathilda sp., AMPG(IV) 2478; B1, B2, Acteon cf. pinguis d’Orbigny, 1852: B1, AMPG(IV) 2479 (SEM image); B2, AMPG(IV) 2479, detail of microsculpture (SEM image); C1, C2, Ringicula minor (Grateloup, 1838), AMPG(IV) 2488; D1-D3, Retusa truncatula (Bruguière, 1792): D1, D2, AMPG(IV) 2541; D3, AMPG(IV) 2542 (SEM image); E1, E2, Pyrunculus sp., AMPG(IV) 2545; F1, F2, Volvulella acuminata (Bruguière, 1792), AMPG(IV) 2547; G1-G3, Pyramidella cf. plicosa Bronn, 1838: G1, G2, AMPG(IV) 2554; G3, AMPG(IV) 2555 (SEM image); H1-H3, ‘Odostomia’ sp. 1, AMPG(IV) 2557; H3, AMPG(IV) 2557 (SEM image); H4, AMPG(IV) 2557, apex (SEM image). Scale bars: A1-A3, C1, C2, E1, E2, F1, F2, G1, G2, H1, H2, 1 mm; B1, 200 µm; B2, H4, 100 µm; D1, D2, H3, 500 µm; D3, G3, 400 µm.