Pyramistomia aliakmoni, 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 : 353-354

Pyramistomia aliakmoni n. sp.

(Fig. 8 E1-E4)

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

TYPE MATERIAL. — Holotype: sample F11: AMPG ( IV) 1500. — Paratype 1: sample F11: AMPG ( IV) 1501. — Paratype 2: sample F11: AMPG ( IV) 1502.

DIMENSIONS. — Maximum height: 1.95 mm; maximum width: 1.00 mm.

ETYMOLOGY. — Named after the river god Aliakmon of Greek mythology (son of Oceanus and Tethys), who lived in the river Aliakmon where the specimen was collected.

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. — Small-sized species of Pyramistomia with pyramidal shape, type C inverted protoconch, smooth whorls, canaliculated suture with distinct axial threads, and single, prominent spiral cord at abapical suture.

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

DESCRIPTION

Small solid pyramidal shell, apex blunt. Protoconch of type C, completely intorted. Teleoconch of 4-4.5 whorls. Suture canaliculated, impressed with distinct axial threads. Prominent spiral cord at abapical suture. Axial sculpture of inconspicuous strongly prosocline irregularly spaced growth lines; spiral threads on base. Columella thickened, with small tooth, bordering a narrow umbilical chink.

REMARKS

This species is set apart from other members of the family by its solid shell, its type C protoconch, and its strong spiral sculpture that consists of a prominent suprasutural spiral cord. Few species of Pyramistomia have been described in the fossil record and recent species are also scarce ( Landau et al. 2013). Pyramistomia deubeli ( Boettger, 1902) is a relatively well-known species from the middle Miocene of Europe (Paratethys, Proto-Mediterranean Sea). It differs from P. aliakmoni n. sp. in its additional spiral cord below the adapical suture and the broader outline. Recent species of Pyramistomia described by Peñas & Rolán (1999) and discussed by Landau et al. (2013) seem to belong to the genus Odostomia , and the placement in a particular genus is uncertain. The recent Odostomia fehrae Van Aartsen, Gittenberger & Goud, 1998 , placed in Pyramistomia by van Aartsen et al. (1998), might rather be related with Eulimastoma according to Pimenta & Absalão (2004).

Figures

FIG. 8. — A1, A2, ‘Odostomia’ sp. 2, AMPG(IV) 2558; B1-B3, Megastomia sp. 1, AMPG(IV) 2560; C1, C2, Brachystomia sp., AMPG(IV) 2570; D1-D3, Megastomia sp. 2: D1, AMPG(IV) 2563;D2, D3, AMPG(IV) 2564;E1-E4, Pyramistomia aliakmoni n. sp.: E1, E2, holotype, AMPG(IV) 1500;E3, paratype 1, AMPG(IV) 1501 (SEM image); E4, AMPG(IV) paratype 1, AMPG(IV) 1501, protoconch (SEM image); F1-F4, Parthenina sp. 1: F1, F2, AMPG(IV) 1573; F3, AMPG(IV) 1574 (SEM image); F4, AMPG(IV) 1574, apex (SEM image); G1, G2, Parthenina sp. 2: G1, AMPG(IV) 2575; G2, AMPG(IV) 2575, apex (SEM image); H,?Syrnola sp., AMPG(IV) 2577 (SEM image). Scale bars: A1, A2, B1-B3, D1, G1, H, 500 µm; C1, C2, D2, D3, E1, E2, 1 mm; E3, F1, F2, 400 µm; E4, F3, 200 µm; F4, G2, 100 µm.