Sarika subheptagyra Pholyotha & Panha sp. nov. Figs 1, 6, 10F, 25E, F, 28, 29, 31E

Type material.

Holotype CUMZ 7506 (Fig. 25E, width 25.5 mm, height 12.5 mm). Paratypes CUMZ 7507 (four shells and six specimens preserved in ethanol; Fig. 25F, width 26.4 mm, height 12.0 mm), CUMZ 7514 (11 specimens preserved in ethanol), NHMUK 20200284 (two shells).

Other material examined.

Thailand-Central. Tham Khao Wong, Ban Rai, Uthai Thani, 15°01'53.4"N, 99°27'21.1"E: CUMZ 7508. Khao Chong Lom, Ban Rai, Uthai Thani, 15°16'51.6"N, 99°43'08.4"E: CUMZ 7509. Wat Khao Chueak Charoen Tham, Ban Rai, Uthai Thani, 15°16'17.2"N, 99°41'43.6"E: CUMZ 7515. Hup Pa Tat, Lan Sak, Uthai Thani, 15°22'33.8"N, 99°37'49.5"E: CUMZ 7510, 7511, 7512, 7513. Wat Thep Muang Thong, Lan Sak, Uthai Thani, 15°24'59.5"N, 99°35'36.6"E: CUMZ 7516.

Type locality.

Tham Namthip Bureau of Monks, Lan Sak, Uthai Thani, Thailand, 15°25'57.5"N, 99°35'19.6"E.

Diagnosis.

Shell large, strongly depressed and pale yellowish brown to pale brown with very rounded body whorl. Animal with grey body and five mantle lobes. Genitalia with a straight epiphallic caecum and triangular prism pilasters on inner penial sculpture. Spermatophore: head filament with irregularly smooth longitudinal ridges; tail filament near sperm sac with three spines and terminal part of tail filament more than more than ca. one-fourth of its length with series of branching spines.

Description.

Shell. Shell strongly depressed, large size (shell width up to 26.4 mm, shell height up to 12.4 mm), and thin. Surface smooth and glossy; shell colour pale yellowish brown to pale brown. Whorls 6- 6½, increasing regularly; body whorl large and well rounded. Spire slightly elevated; suture impressed. Aperture crescent-shaped and opening obliquely. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 25E, F).

Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. one-third of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid with acute angle on top (triangular prism). Epiphallus cylindrical, long and approximately one and half times as long as penis. Epiphallic caecum short, straight, and located proximally near middle of epiphallus, penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long and slender, approximately as long as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 28).

Vagina cylindrical and approximately as long as penis. Dart apparatus large, long cylindrical, located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long, cylindrical. Free oviduct cylindrical, longer than vagina and proximal end encircled with thick tissue (Fig. 28A).

Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly smooth longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I simple and rather short. Spine II large and long and branching into very small spinules. Spine III relatively smaller than spine II and branching into very small spinules. Region furthest away smooth and without spine; terminal part (more than ca. one-fourth of its length) with series of long branching spines into spinules arranged in a row, and then transformed to very long serrate-like spines arranged in opposite rows near the tail filament tip (Fig. 29).

Radula . Teeth with half row formula: 1-(14-15)-68. Central tooth symmetrical tricuspid; lateral teeth asymmetrical tricuspid; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 14 or 15 (Fig. 31E).

External features. Animal with reticulated skin and pale to dark grey body. Foot sole and caudal foss present; caudal horn raised. Five mantle lobes well developed and same colour as body (Fig. 10F).

Etymology.

The specific name subheptagyra is derived from the Latin word sub meaning under, from, somewhat, and less than, and the word heptagyra referring to shell similar to S. heptagyra .

Distribution.

This species occurs only in Uthai Thani Province and is restricted to limestone habitats (Fig. 6).

COI analysis.

The ML and BI analyses indicated that the samples of S. subheptagyra sp. nov. (n = 3) formed a monophyletic group with good support (Fig. 1; BS = 90%, PP = 1). The mean intraspecific genetic distance of S. subheptagyra sp. nov. was 2.4% (Table 2).

Remarks.

Sarika subheptagyra sp. nov. differs from S. heptagyra in having longer vagina and free oviduct, and triangular prism-shaped penial pilasters, while S. heptagyra have cuboidal penial pilasters. Moreover, the COI sequence divergences between them is high (7.9%).

Compared with S. resplendens, S. subheptagyra sp. nov. has a longer vagina and free oviduct, thin penial retractor muscle, and triangular prism-shaped penial pilasters. Sarika resplendens has a shorter vagina and free oviduct, a very large and thickened penial retractor muscle, and cuboidal-shaped penial pilasters. Additionally, the genetic distance between both species is fairly high (6.5%).

Sarika subheptagyra sp. nov. differs from S. caligina sp. nov. in having a lower spire, longer vagina, and free oviduct, and spine II and spine III on spermatophore start branching near the base, while S. caligina sp. nov. has a higher spire, shorter vagina and free oviduct, and spine II and spine III on spermatophore start branching near the tip. In addition, the genetic distance between these two new species is high (8.2%).