Alvania amphitrite, Thivaiou & Harzhauser & Koskeridou, 2019

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 : 340

Alvania amphitrite n. sp.

(Fig. 5 G1-G4)

urn:lsid:zoobank.org:pub:A2760279-BE3E-4730-9688-9AB777F3A357

TYPE MATERIAL. — Holotype: AMPG ( IV) 1503, height 2.50 mm. — Paratype 1: AMPG ( IV) 1504, 2.20 mm. — Paratype 2: AMPG ( IV) 1505, height 1.95 mm.

DIMENSIONS. — Maximum height: 2.50 mm; maximum width: 1.70 mm.

ETYMOLOGY. — Named after the Nereid Amphitrite of Greek mythology, wife of Poseidon and protector of marine animals (as noun in apposition).

TYPE LOCALITY. — Felli village section, 40°01’4.55”N, 21°33’34.37”E, Mesohellenic Basin, Grevena area, Greece.

TYPE LEVEL. — Pentalofos Formation, Aquitanian, lower Miocene.

DIAGNOSIS. — Shell small; protoconch consisting of about 2.5 whorls. Sculpture reticulated, ad- and abapical spiral cords strengthened, whorls flat, suture deep. Last whorl tall and rounder; aperture wide, teardrop-shaped.

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

DESCRIPTION

Small, ovoid species; protoconch of 2.5 rounded smooth whorls, measuring 0.29 mm in height and 0.34 mm in width. Teleoconch of 3.5-4 flat whorls, last whorl occupies approximately 70% of total length. Sculpture consisting of 12 axial ribs and 6 spiral cords; second and last spiral cords stronger, middle cords more closely-spaced. Base with 5 spiral cords and faint axial riblets; no umbilicus; aperture wide, tear-drop shaped; outer lip somewhat inflated.

REMARKS

The protoconch whorls are convex whereas the teleoconch whorls are flat. The spiral sculpture bears a prominent first adapical spiral cord which forms a weak subsutural collar. The spiral cords are regularly spaced except for the first (adapical) and last (abapical) cords which have a slightly larger space between the central cords of the spire. The reticulated aspect of the sculpture is maintained on the base of the shell.

The present species has a sculpture that is quite similar to Alvania oceani (d’Orbigny, 1852) but differs consistently in having a more prominent sculpture, with ribs being less prominent than in A. oceani; other differences include the absence of varices on early teleoconch whorls, the absence of an umbilical chink, and the overall shape being less elongated than in A. oceani. Another similar species from the Aquitanian of SW France is Alvania mariae (d’Orbigny, 1852) which has flat early teleoconch whorls, a thicker shell, about 7 axial ribs and a smaller aperture.

Alvania areolifera (Sandberger, 1863) from the Oligocene of the Paratethys, as illustrated by Garilli & Parrinello (2014), has a similar spiral sculpture with closely-spaced spiral cords at the middle of each whorl, but this species has a thicker shell, more prominent axial sculpture and finer and more numerous spiral cords.

Alvania critica Boettger, 1907 differs in having a more pronounced axial sculpture and a smaller aperture as illustrated from the middle Miocene of Turkey ( Landau et al. 2013). Alvania perregularis (Sacco, 1907) has a more elongated aspect, a more finely reticulated teleoconch sculpture, a more prominent subsutural collar and a smaller aperture ( Landau et al. 2013).

Figures

FIG. 5. — A1, A2, Nodiscala cf. rugatina de Boury in Cossmann, 1912: A1, A2, AMPG(IV) 2335; B1, B2, Triphora (s.l.) sp.: B1, AMPG(IV) 2439 (SEM image); B2, AMPG(IV) 2439, protoconch (SEM image); C1-C4, Metaxia sp.: C1, AMPG(IV) 2443, protoconch (SEM image); C2, AMPG(IV) 2443 (SEM image); C3, C4, AMPG(IV) 2443; D1-D3, Dizoniopsis sp.: D1, D2, AMPG(IV) 2445; D3, AMPG(IV) 2446 (SEM image); E1, E2, Rissoina subconoidea (Grateloup, 1847); E1, E2, AMPG(IV) 2448; F1, F2, Zebinella sp., AMPG(IV) 2451; G1-G4, Alvania amphitrite n. sp.: G1, G2, holotype, AMPG(IV) 1503; G3, paratype 2, AMPG(IV) 1505 (SEM image); G4, paratype 2, AMPG(IV) 1505, protoconch (SEM image); H1-H4, Alvania transiens (Sacco, 1895): H1, H2, AMPG(IV) 2455; H3, AMPG(IV) 2456 (SEM image); H4, AMPG(IV) 2456, protoconch (SEM image); I1, I2, Xenophora sp., AMPG(IV) 2461. Scale bars: A,D1-D3, F1, F2, G1, G2, H1-H3, 1 mm; B1, C2-C4,E1, E2, G3,500 µm; B2, H4, 400 µm; C1, G4, 200 µm; I1, I2, 2 mm.