Taphrenalla incilis 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 : 63-64

Taphrenalla incilis Pholyotha & Panha , sp. nov.

( figs 1 , 3 , 10D, 12D–F, table 6)

Type material examined. Holotype: CUMZ 7207 (fig. 10D). Paratypes. Same data as holotype: CUMZ 7208 (four shells and five specimens in ethanol) , CUMZ 7209 (six shells and six specimens in ethanol) , NHMUK (two shells) , and SMF (two shells) .

Type locality. Tham Khao Ting, Palian District, Trang, Thailand (7°09’30.0”N, 99°48’06.0”E) .

Etymology. The specific epithet “ incilis ” is from the Latin word “ incile ” meaning “ditch, trench”, which referrs to the characteristic small radial grooves in the shell sculpture.

Diagnosis. Shell with narrow and deep channel-shaped suture, and weak and short radial grooves. Epiphallic caecum short and bent at tip. Penial caecum short. Inner sculpture of proximal penis with very small longitudinal folds; distally narrow and obliquely cuboidal folds. Dart apparatus located at vagina and penis junction. Spermatophore with two spines on tail filament close to sperm sac.

Description

Shell (fig. 10D). Shell comparatively depressed conic, moderate-sized (width up to 16.1 mm; height up to 8.8 mm) and pale to dark brown. Whorls 5–6; suture narrow, deep grooved, and channel-shaped. Upper shell surface with numerous, very short and weak radial grooves near suture and then suddenly disappear. Spire depressed conic; apex raised with a spire angle of about 134–151°. Last whorl barely shouldered, and periphery almost rounded. Aperture lip simple; ummbilicus narrowly opened.

Genital organs (figs 12D–F). Atrium short. Penis cylindrical and around three times total vagina length; penial caecum present. Inner sculpture of proximal and middle part of penis with fine longitudinal folds; distal portion with narrow obliquely cuboidal penial pilasters surrounding penial verge. Epiphallus slender tube and slightly longer than penis. Epiphallic caecum short and bent at tip; thick penial retractor muscle connecting near the tip. Flagellum short, irregular curved and with obtuse tip. Vas deferens thin tube. Vagina prolonged, cylindrical-shaped. Dart apparatus located at junction of vagina and penis. Spermatophore long and needle-shaped. Tail filament very long tube; region close to sperm sac bearing two spines; spine near sperm sac very small and shorter than the other.

External features ( fig. 3 ). Animal dark gray in body colour with a pale milky yellow stripe at middle of the body running from head to caudal horn. Posterior part (body to tail) with pale milky yellow colour and wider stripe than anterior part (head to body).

Remarks. The weak radial grooves on the upper shell surface of T. incilis sp. nov. is similar to T.parversa sp. nov., T. conformis sp. nov., and T. pygmaea sp. nov. However, together with the suture shape and genitalia, T. incilis sp. nov. have a deeper and wider suture than T. parversa sp. nov. and T. conformis sp. nov. The dart apparatus of T. parversa sp. nov. and T. conformis sp. nov. is located on the proximal vagina away from the penis junction, while T. incilis sp. nov. has the dart apparatus joining at the junction of vagina and penis.

While the suture shape and position of dart apparatus of T. incilis sp. nov. is similar to T. pygmaea sp. nov., T. incilis sp. nov. have a bent epiphallic caecum, and short flagellum and vagina, whereas T. pygmaea sp. nov. have a straight epiphallic caecum, and long flagellum and vagina.

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.