Taphrenalla pygmaea Pholyotha & Panha, 2021

Pholyotha, Arthit, Sutcharit, Chirasak, Tongkerd, Piyoros, Jeratthitikul, Ekgachai & Panha, Somsak, 2021, Integrative systematics reveals the new land-snail genus Taphrenalla (Eupulmonata: Ariophantidae) with a description of nine new species from Thailand, Contributions to Zoology 90 (1), pp. 21-69 : 64-66

Taphrenalla pygmaea Pholyotha & Panha , sp. nov.

( figs 1 , 3 , 13A, 14A, B, table 6)

Type material examined. Holotype: CUMZ 7210 (fig. 13A). Paratypes. Same data as holotype: CUMZ 7211 (19 shells and 12 specimens in ethanol), NHMUK (two shells), and SMF (two shells) .

Other material examined. Wat Sathit Khirirom, Khiri Rat Nikhom District, Surat Thani (9°01’48.2”N 98°59’12.5”E): CUMZ 7212 (75 shells and nine specimens in ethanol) .

Type locality. Tham Wang Badan Priest’s Camp Site, Khiri Rat Nikhom District, Surat Thani, Thailand (8°54’21.9”N 98°56’53.9”E) .

Etymology. The specific epithet ‘ pygmaea ’ is from the Latin word ‘ pygmaeus ’ meaning ‘dwarf’, which referrs to it being the smallest sized snail in this genus.

Diagnosis. Shell small to medium-sized, narrow and deep channel-shaped suture, and weak, diminutive radial grooves. Epiphallic caecum straight. Penial caecum short. Inner sculpture of proximal penis with very fine longitudinal folds and then transition to oblique and transverse folds distally. Dart apparatus located at junction of vagina and penis.

Description

Shell (fig. 13A). Shell moderately depressed conic, small to nearly medium-sized (width up to 12.3 mm; height up to 6. 8 mm) and pale brown. Whorls 5–6; suture narrow, deep, and channel-shaped. Upper shell surface with weak and diminutive radial grooves that appear only near suture. Spire deressed conic; apex raised with a spire angle of about 131–151°. Last whorl barely shouldered and periphery almost rounded. Aperture lip simple; umbilicus narrowly opened.

Figure 13 Shells. A. Taphrenalla pygmaea sp. nov. holotype CUMZ 7210. B. T. zemia sp. nov. holotype CUMZ 7213. C. T. alba sp. nov. holotype CUMZ 7217. Inset SEM image showing shell sculpture of each species.

Genital organs (figs 14A, B). Atrium short. Penis funnel-shaped and slightly longer than vagina; penial caecum present. Inner sculpture of proximal penis with very fine longitudinal penial pilasters, gradually transforming to oblique and transverse folds surrounding penial verge. Epiphallus cylindrical-shaped, about one and half times total penis length. Epiphallic caecum short, and attached with thin penial retractor muscle. Flagellum prolonged and cylindrical with blunt tip. Vas deferens small tube. Vagina long and cylindrical-shaped. Dart apparatus located at junction of proximal vagina and proximal penis.

Figure 14 Genitalia. A, B. Taphrenalla pygmaea sp. nov. paratype CUMZ 7211. A. whole reproductive system. B. internal wall of penis with penial verge. C. T. zemia sp. nov. paratype CUMZ 7214, whole reproductive system from juvenile specimen.

External features ( fig. 3 ). Animal very dark gray in body colour with indistinct pale milky stripe at middle of the body running from head to caudal horn.

Remarks. Taphrenalla pygmaea sp. nov. is distinctive in being the smallest of the known Taphrenalla species. Compared to T. incilis sp. nov., this new species is distinguished by a small shell with narrow body whorl. Moreover, the internal distal penial surface of T. pygmaea sp. nov. has oblique and transverse folds whereas the distal portion of T. incilis sp. nov. has narrow obliquely cuboidal pilasters.

Figures

Figure 1 Map showing the sampling sites of the 11 Taphrenalla species along Southern Thailand.Each colour of the distribution range follows the phylogenetic tree of all Taphrenalla species in fig.3.

Figure 3 A representative ML tree showing only the Taphrenalla clade.The synopsis of the radial groove on shell sculpture, genitalia showing location of dart apparatus, and live specimens of Taphrenalla spp. Results of species delimitation analyses based on the COI gene using ABGD and PTP.Black circles represent nodes with both ML (when Ē 70%) and BI (when Ē 0.95) support.White circles represent nodes with ML BS support but no BI PP support (when <0.95). Each clade colour refers to the distribution range in fig. 1.