Tortaxis cylindropsis Man & Panha, 2024

Man, Nem Sian, Ablett, Jonathan D., Lwin, Ngwe, Sutcharit, Chirasak & Panha, Somsak, 2024, Contributions on a small collection of the former Subulinidae Fischer & Crosse, 1877 (Eupulmonata, Achatinoidea) with catalogue of the Glessula and Rishetia species recorded from Myanmar, ZooKeys 1208, pp. 173-239 : 173-239

38 Tortaxis cylindropsis Man & Panha sp. nov.

Fig. 16 G – I , Table 1

Type specimens.

Holotype CUMZ 13079 (height 9.6 mm, width 2.3 mm; Fig. 16 G ) , paratypes CUMZ 13080 (35 shells; Fig. 16 H, I ) , NHMUK 20230919 (2 shells) and SMF (2 shells).

Type locality.

Parpant area, Taunggyi City, Taunggyi District, Shan State, Myanmar (20 ° 15 ' 3.7 " N, 97 ° 14 ' 23.9 " E).

Etymology.

The specific name cylindropsis is from the Latin word for cylinder, and the Greek suffix - opis means ‘ having the appearance of or like’. It refers to the cylindrical shell shape of this species.

Diagnosis.

Shell slender cylindrical, suture deeply impressed, spire distinctly turreted, protoconch rounded and smooth, subsequent whorls with fine growth lines and a distinct spiral fold on columellar margin.

Description.

Shell (height 9.3–11.7 mm) slender cylindrical in shape ,, translucent, whitish to pale yellowish colour, and with 8–9 ½ whorls. Apex rounded; protoconch ~ 2 whorls, rounded and with smooth surface; subsequent whorls with fine growth lines more distinct on last whorl. Spire high, grows evenly and is largely turreted; whorls flatly convex; last whorls slightly larger than preceding whorls; suture narrow, deep, and weakly crenulated. Aperture vertical, narrowly ovate, and elongate; peristome thin; columella straight; columellar margin slightly expanded with distinct spiral fold. Umbilicus closed.

Distribution.

This species is known only from its type locality.

Differential diagnosis.

Comparing this new species with the Vietnamese species, T. comaensis Do, 2014 has a much larger and taller shell (height 56.1–66.4 mm), an attenuated spire, coarser sculptures, a broad aperture, and a thickened peristome, whereas this new species display a much smaller shell (height 9.3–11.7 mm), grows evenly and has a cylindrical spire, smooth shell surface, narrow aperture, and thin peristome ( Do and Do 2014). Tortaxis erectus ( Benson, 1842) has a less turreted shell, wide and flatly convex whorls, and a shallow suture (Fig. 16 A ), while T. cylindropsis sp. nov. has a distinctly turreted, slender shell with narrow and convex whorls, and a deep suture. Tortaxis elongatissimus Bavay & Dautzenberg, 1909 possesses a more elongated shell with stronger radial ribs and a more attenuated spire (Fig. 16 B ) than this new species. Tortaxis lubricus Pilsbry, 1906 has a broad last whorl, attenuated spire, wider aperture, and shallow suture (Fig. 16 C ); in contrast, the shell of T. cylindropsis sp. nov. presents narrowly and even whorls, cylindrical, slender, and turreted spire, narrow aperture, and deep suture. Tortaxis papillosa Dautzenberg & Fischer, 1908 shows a broad shell with an attenuated spire, rounded embryonic whorls, flatter whorls, and a shallow suture (Fig. 16 D ), whereas T. cylindropsis sp. nov. has a slender shell, with cylindrical spire, convex whorls, and deeper suture. Tortaxis permira (Ancey in Bavay & Dautzenberg, 1904) and T. pilsbryi (Ancey in Bavay & Dautzenberg, 1904) have a wider shell, with a shallower suture, gradually attenuated spire, and an aperture wider than that of T. cylindropsis sp. nov. (Fig. 16 E, F ).

Remarks.

This genus is reported for the first time in Myanmar, and the present finding expands the distribution range of the genus from China, Vietnam, Laos, and Thailand to include Myanmar.

Figures

Figure 16. A Tortaxis erectus, neotype NHMUK 1991104 A from Nanking, China B Tortaxis elongatissimus, syntype MNHN - IM- 2000-4705 from Pac-Kha C Tortaxis lubricus, holotype ANSP 66056 from near Haiphong D Tortaxis papillosa, MNHN - IM- 2000-33971 from Nam-Nhang E Tortaxis permira, syntype MNHN - IM- 2000-4675 from That-Khé, Tonkin F Tortaxis pilsbryi, syntype MNHN - IM- 2000-4678 from Bac-Khan et That-Khé G – I Tortaxis cylindrotis sp. nov. G holotype CUMZ 13078 from Taunggyi, Shan State, Myanmar with embryonic whorls and aperture H, I paratypes CUMZ 13079 from the type locality H probably juvenile shell with 7 whorls and I adult shell. Photographs: P Bourguignon & D Brabant (B, D – F).