Gastroptychia collicola, Chen & Ablett, 2024

Chen, Zhe-Yu & Ablett, Jonathan D., 2024, Two new Gastroptychia Kobelt & Möllendorff, 1900 from Darjeeling and West Khasi Hills, northeastern India (Gastropoda: Cyclophoroidea: Diplommatinidae), Zootaxa 5538 (1), pp. 79-88 : 80-82

Gastroptychia collicola sp. nov.

( Figure 1 )

Type specimens. Holotype: NHMUK 20240383/1 (1 specimen), labels: Shillong, Khasi, low ground [on the box]; Shillong Station , low ground [in the vial]. [current geopolitical location: Shillong, East Khasi Hills , Meghalaya, India]. H. H. Godwin-Austen Collection . Paratypes: NHMUK 20240383/2-11 (10 specimens, one was broken for study, as NHMUK 20240383/2), same data as holotype .

Etymology. This name comes from the Latin word collis (hill) with the suffix -cola (dweller), as the type locality is famous for its rolling hills.

Diagnosis. Gastroptychia collicola sp. nov. is characterized by the ovately fusiform shell and widely spaced ribs, with a palatal swelling situated on ventrolateral side of the body whorl, a strong horizontal palatal lamella presents just after and a strong and twisted columellar lamella.

Description. Shell small, sinistral, pale with brown hue, ovately fusiform, with 5.25 convex whorls; suture impressed; apex blunt; penultimate whorl widest; lateral side of the body whorl very flattened in aperture view. Protoconch consisting of 1.25 whorls, somewhat matte with very fine radial threads; boundary between protoconch and teleoconch clear. Teleoconch surface with fine and regularly arranged radial and prosocline ribs, approximately 9 ribs on the penultimate whorl when view from the aperture side, very weak and dense spiral threads situated only on the lower part of the body whorl. A palatal swelling situated on ventrolateral side of the body whorl, attached to the aperture. Aperture oval, vertical. Peristome double, spaced, upper part largely attached to the body whorl, nearly reaching the penultimate whorl, but with margin distinctly detached; outer peristome expanded, at the same height as inner peristome, with an inconspicuous curved columellar lip, visible from aperture view; inner peristome expanded but not reflected. Internal constriction distinctly presents ventrally with a thin basal radial (to the shell axis) palatal fold. A small parietal lamella presents near the constriction. A strong horizontal palatal lamella presents just anterior to the swelling, situated from lateral side to dorsal side. Columellar lamella large, oblique, interior part distanced with constriction; columellar tooth emerged from aperture, downward sloping. Umbilicus closed. Operculum corneous, thin, translucent, light amber coloured; nucleus not observed.

Measurements. Shell height: 1.98 mm, shell width: 1.20 mm, aperture height: 0.91 mm, aperture width: 0.81 mm (holotype).

Differential diagnosis. The palatal swelling of the new species cannot be found in all the other Gastroptychia . This new species resembles sympatric species Gastroptychia gibberosa ( Godwin-Austen, 1892) , Gastroptychia gibbosa (W. T. Blanford, 1868) and Gastroptychia jaintiaca ( Godwin-Austen, 1870) from Meghalaya and Manipur, India in general shell shape. The new species is distinguished from latters by its smaller shell size (shell height: 2 mm vs 2.5–3.2 mm), the distinctive palatal swelling and palatal lamella. Gastroptychia formosana ( Pilsbry & Hirase, 1906) from Taiwan Island is also similar to the newly described species. However, aside from the absence of palatal swelling and lamellae, the former species has sparser ribs.

Remarks. The type specimens in lot NHMUK 20240383 were separated from a mixed lot registered as NHMUK 1903.7.1.3597 from the Godwin-Austen collection, containing 25 dextral specimens and provisionally labelled with a note from Godwin-Austen that reads “ D. nr sherfaiensis ” which we assume stands for near Diplommatina sherfaiensis Godwin-Austen, 1870 .

Distribution. INDIA: Meghalaya. The new species is known only from the type locality.

Figures

FIGURE 1. Gastroptychia collicola sp. nov. A–C. holotype NHMUK 20240383/1. A. Shell overview. B. Enlarged lateral view. C. Enlarged dorsal view. D. paratype NHMUK 20240383/2, show internal structure. E. Original label of the collection.