Mathilda sp., Semper, 1865

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 : 345-346

Mathilda sp.

(Fig. 7 A1-A3)

MATERIAL EXAMINED. — Sample F10: AMPG ( IV) 2478 (one specimen).

DIMENSIONS. — Height: 3.14 mm.

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

DESCRIPTION

Elongated turriculate shell; apical angle c. 29°. Protoconch consisting of two whorls, smooth, bulbous, perpendicular to the teleoconch; diameter 500 µm. Teleoconch with relatively flat whorls; sculpture consisting of three equidistant spiral cords; two cords placed immediately below adapical and above abapical suture; third cord in mid-whorl, more prominent. Fourth very fine spiral cord appears between adapical two cords on fourth teleoconch whorl. Axial sculpture of regularly spaced fine riblets, forming beads at intersections with spiral cords. Suture impressed, emphasized by adjoining beaded spiral cords; aperture missing.

REMARKS

Mathilda peyroti ( Cossmann & Peyrot 1922) is the most similar species, with the main difference being that the fourth, finer cord appears on whorl 5 of the teleoconch.The apical angle ranges from 20 to 23° for M. peyroti ( Cossmann & Peyrot 1922), whereas for the present specimen it is of about 29°. The present species also differs from M.granosa (Borson, 1821) , in having less prominent sculpture and a thicker cord below the suture. Another Miocene species is M. margaritula, which differs mainly by forming more prominent nodes at the intersections of cords and axial ribs.

According to Gründel & Nützel (2013), Mathildidae feed on Cnidaria.

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.