Taphrenalla parversa Pholyotha & Sutcharit & Tongkerd & Jeratthitikul & Panha 2021, sp. nov.

Taphrenalla parversa Pholyotha & Panha, sp. nov.

(figs 1, 3, 10B, 11D–F, table 6)

Type material examined. Holotype: CUMZ 7199 (fig. 10B). Paratypes. Same data as holotype: CUMZ 7200 (one shell and five specimens in ethanol), CUMZ 7201 (five shells), NHMUK (two shells), and SMF (two shells).

Type locality. Tham Suwan Khuha, Takua Thung District, Phang-nga, Thailand (8°25’45.0”N, 98°28’19.6”E).

Etymology. This species is derived from ‘ parv ’ (the Latin word ‘ parvus ’) meaning ‘little’ and ‘ versa ’ (the Latin word ‘ versus ’) meaning ‘line, furrow’ with reference to the characteristic numerous little radial grooves on the shell sculpture.

Diagnosis. Shell with shallowly impressed suture and very weakly radial grooves. Penis with thick penial sheath. Penial caecum absent. Epiphallic caecum straight. Inner sculpture of proximal penis with fine, irregular and longitudinal folds, and then trasition to irregular and zig-zag, longitudinal folds distally. Dart apparatus connected on vagina. Spermatophore with two spines on tail filament close to sperm sac.

Description

Shell (fig. 10B). Shell comparatively depressed conic, medium-sized (width up to 14.4 mm; height up to 8.1 mm) and pale brown. Whorls 5–6; suture shallowly impressed. Upper shell surface with numerous weak radial grooves continuing from suture and disappear before periphery. Spire depressed conic; apex raised with a spire angle of about 142–164°. Last whorl barely shouldered and rounded periphery. Aperture lip simple; umbilicus narrowly opened.

Genital organs (figs 11D–F). Atrium very short. Penis stout cylindrical and about same length as vagina; penial caecum absent. Inner sculpture of proximal penial wall with fine irregular longitudinal penial pilasters and then gradually irregular, zig-zag, longitudinal folds in middle and surrounded penial verge. Epiphallus slender tube, around two times total penis length, and smaller diameter than penis; proximal epiphallus larger than distal portion. Epiphallic caecum short,same diameter as proximal epiphallus, and attached with thick penial retractor muscle. Flagellum short with irregular shape. Vas deferens small tube. Vagina very enlarged, cylindrical-shaped, and distal part enlarged. Dart apparatus located on proximal vagina away from penis joining to atrium. Spermatophore elongate and needle-shaped. Tail filament very long tube; region close to sperm sac bearing two spines; spine located close to sperm sac smaller and shorter than the other.

External features (fig. 3). Animal dark gray colour on head to body with three bright orange stripes running from head to body (two stripes near foot sole and one at middle of body), and then gradually only bright orange stripes on body to tail.

Remarks. Taphrenalla parversa sp. nov. is similar to T. corona sp. nov. because of the absence of the penial caecum and a thick penial sheath. However, they can be discriminated by their flagellum, epiphallus, vagina, and shell morphology. Taphrenalla parversa sp. nov. has a shorter flagellum, longer epiphallus, and larger vagina than T. corona sp. nov. In shell comparison, T. parversa sp. nov. has a weakly impressed suture and very weakly radial grooves on the shell sculpture, whereas T. corona sp. nov. exhibits a wide and deep groove at suture and deep radial grooves on the shell sculpture.