Chamalycaeus, von Mollendorff, 1897

Chamalycaeus View in CoL aduncus

Jirapatrasilp sp. nov.

( Figs 1–3 View FIG View FIG View FIG )

Zoobank registration: urn:lsid:zoobank.org:act:

068B2DC0-BC09-4BA7-80B0-E8592A1D88FD

Type material: Holotype CUMZ 14461 View Materials ( Fig. 1 View FIG ), paratypes CUMZ 14462 View Materials (25 shells; Fig. 2 View FIG ), NHMUK 20250001 About NHMUK (3 shells) and SMF 380296 About SMF (3 shells) from Locality C 110, Temple in Kantueu Pir (Kantueu Hill), Banan, Battambang, Cambodia, 12°54’15.7”N, 103°07’13.1”E ( Fig. 3 View FIG ), 2Aug 2024, coll. W. Siriwut, C. Sutcharit. GoogleMaps

Diagnosis: SH up to 2.0 mm, SW up to 2.7 mm, depressed-conical. Spire ca. 1/4 of shell height. Spiral striation with 11–13 spiral striae at apical view. R1 ca. 1¼ whorls with regular ribs; R2 ca. 1/5 whorl and nearly as long as R3; R2 with ca. 22 ribs. R3 strongly coils downwards, being highly oblique to the shell’s horizontal axis, expanding near the end of the aperture.Aperture round. Inner peristome sharp, protruding. Outer peristome thickened, multilayered expanded; palatal to basal edge expanded, columellar to parietal edge not expanded, basal edge triangular and bending inwards, appearing beak- or hook-like. Umbilicus round.

Description: SH up to 2.0 mm, SW up to 2.7 mm, depressed-conical, solid, translucent, yellowish to pale crimson. Shell outline oval in apical view, spire ca. 1/4 of shell height. Whorls ca. 3¾–4. Protoconch low, ca. two whorls, glossy, smooth, without spiral striation. Spiral striation starts from R1, continuing to the end of aperture, with 11–13 spiral striae at apical view, spiral striation weaker than radial ribs in R1 and R2. R1 ca. 1¼ whorls, with fine, regular ribs; with ca. 13 ribs in ¼ whorl adjoining R2. Boundary between R1 and R2 distinct as R2 contains more close-set and thicker ribs than R1; R2 with ca. 22 ribs that are curved towards aperture, ribs less thickened at the beginning and the end of R2; R2 ca. 1/5 whorl and nearly as long as R3. Boundary between R2 and R3 distinct due to very shallow constriction; R3 with indistinct growth lines, strongly coils downwards being highly oblique to the shell’s horizontal axis, expanding near the end of the aperture. Last whorl with bluntly shouldered and ended around the beginning of R3. Aperture round; opening obliquely downwards. Peristome double with prominent outer peristome. Inner peristome sharp, protruding. Outer peristome thickened, multilayered (visible in lateral view); palatal to basal edge expanded, columellar to parietal edge not expanded, basal edge triangular and bending inwards, appearing beak- or hook-like. Umbilicus round, open, approximately one third of shell width, and with weakly blunt-periumbilical ridge that ended around the beginning of R3. Operculum unknown.

Etymology: The specific epithet is derived from the Latin word ‘uncus’ meaning ‘hook, barb or bent’. The epithet aduncus refers to the basal edge of the outer lip bending inwards and appearing beak- or hook-like.

Distribution and habitat: Known only from the type locality in Kantueu Hill, Battambang, Cambodia. The Kantueu Hill is an isolated limestone outcrop located south of Battambang town. The hill is about 400 m wide and surrounded by agricultural areas and temple buildings. The vegetation of this hill is a deciduous forest with moderate disturbance by clear- ing or mowing of low vegetation and with evidence of fire. The specimens examined herein are empty shells, which were collected from the topsoil under the leaf litter near rock base or crevices.

Remarks: Among all Chamalycaeus species, there are only three taxa where the R3 strongly coils downwards, being highly oblique to the shell’s horizontal axis. They are Chamalycaeus aduncus sp. nov., C. excisus excisus (von Möllendorff, 1887) and C. excisus sublimus Páll-Gergely et Auffenberg, 2019 ; the latter two being from the Philippines [ Páll-Gergely, Auffenberg, 2019]. These three species are also similar in shell size and depressed-conical shell shape. However, this new species differs from both C. excisus excisus and C. excisus sublimus in having a shorter R2 without any blunt keel, a round aperture without any incision, and a beak- or hook-like basal edge of the outer peristome ( Fig. 1B View FIG ).

The aperture of Chamalycaeus aduncus sp. nov. is also similar to C. serratus Páll-Gergely et Auffenberg, 2021 and C. krabiensis Páll-Gergely et A. Reischütz, 2021 from Thailand [ Páll-Gergely et al., 2021]. However, the basal edge of the outer peristome in this new species is triangular and highly bending inwards, appearing beak- or hook-like. Moreover, the new species has a shorter R2 with less ribs, and a more bluntly shouldered last whorl.

Five shells out of the 32 examined specimens had a scraping hole. It is possible that these specimens were predated by the carnivorous micro land snail Diaphera saurini Benthem Jutting, 1962 , as they were found abundant at this locality.