Megavitrina imperatoria, Ruud, A. Bank, Henk P. M. G Menkhorst & Eike Neubert, 2016

Ruud, A. Bank, Henk P. M. G Menkhorst & Eike Neubert, 2016, Descriptions of new and little-known land snail taxa from Turkey, and establishment of a new genus (Gastropoda, Pulmonata: Lauriidae, Enidae and Vitrinidae), Basteria 80 (1), pp. 5-30 : 26

Megavitrina imperatoria spec. nov. ( Fig. 21 )

“a hitherto undescribed species from eastern Anatolia” – Neubert, 1998: 449.

Type locality & type specimens. – Vilayet Adıyaman, summit Nemrud Dağ (= Commagenes ), 2150 m (37.9799°N 38.7406°E), H.P.M.G. Menkhorst leg., 14.vii.1986. Holotype NMBE 548324 , paratypes NMBE 548345/1, HMK/2 + 6 subadult shells + 5 juveniles. In addition 2 paratypes in HMK (1 adult, 1 subadult) collected at 15.v.2011. Most of the type specimens are partially broken.

Diagnosis. – See the diagnosis of the genus.

Description. – Shell thin and transparant, discoidal in profile, orthostyl, with a pale greenish tinge. Protoconch (1.7 whorls; diameter 2.4-2.7 mm) very finely punctate; the very fine pits are more or less arranged in spiral rows. Teleoconch without punctation; only weak irregularly spaced radial growth lines are present and some hardly visible (even at high magnification) spiral striae. Radial growth lines can also be

present on the protoconch. The first whorls are rather convex, but the last whorl is rather flattened; the suture is shallow. The spire is small and low. The 3.4 whorls (counting according to Knipper, 1939: 332) enlarge rapidly, the last one being very wide. Last whorl forming distinctly less than half the total breadth as viewed from above, slightly descending, convex and never angled at its periphery. Apertural lip simple, thin and delicate; a membranous margin is lacking (or a mere trace only). The upper part of the columellar peristome is reflexed and therefore markedly thickened, closing the umbilicus completely. A remarkable feature of the shell is the presence of 2 to 3 very clear growth interruptions. The interruption can also been observed at the inside of the aperture, namely as a radial, whitish, callus.

Measurements (n = 3). – Shell height 8.9-9.4 (mean 9.1); last whorl height 8.4-8.8 (mean 8.5); maximum height of peristome 5.3-5.6 (mean 5.4); height of spire 0.6-0.8 (mean 0.7) mm; maximum diameter of shell 16.1-17.1 (mean 16.4); minimum diameter of shell 12.6- 13.4 (mean 13.0); maximum diameter of peristome 10.8-11.2 (mean 11.0); diameter last whorl 6.6-7.1 (mean 6.9). The reported maximum diameter of the shell of V. libanica is around 15 to 16 mm ( Germain, 1911: 32; Tohmé & Tohmé, 1988: 71), and the reported maximum shell height of V. libanica is 9 mm.

Localities. – Known from the locus typicus only (see above).

Derivatio nominis. – Named after the emperor Antiochus I Theos Dikaios Epiphanes Philorhomaios Philhellen, who ruled the Kingdom of Commagene between 70 BC and 38 BC. He is the most famous emperor of that kingdom; the ruins of his tomb-sanctuary is atop Nemrud Dağ, being the type locality of this species.

Differentiation. – Megavitrina imperatoria has, compared to M. libanica , a more depressed and a more oval (due to the more expanded aperture) shell, a slightly less pronounced punctate sculpture on the protoconch, and a fewer number of radial growth lines on the teleoconch. We have two specimens of V. libanica at our disposal from the MNHN, with the label: “Beyrouth?”.

Figures

Figs 21 - 23. Megavitrina from Turkey and Lebanon. 21, Megavitrina imperatoria spec. nov., holotype NMBE 548324 (D = 16.2 mm), Turkey, Vil. Adıyaman, under rocks on top of the Nemrud Dağ, 2150 m. 22 - 23, Megavitrina libanica (Germain, 1911), MNHN (D = 15.3 mm), labelled as “ Beyrouth? ”. All photographs Bochud & Neubert, × 5.