Dicharax umashaankeri Páll-Gergely & Aravind, 2025

Dicharax umashaankeri Páll-Gergely & Aravind sp. nov.

urn:lsid:zoobank.org:act:

Figs 65D–F, 66C–D, 73

Diagnosis

A small species of Dicharax with glossy R1 and R3, a combined R2+R3 length of ca 150 degrees, an R3 with a clearly separated main swelling and a secondary swelling, and a rounded aperture with a slight upper incision.

Etymology

This species is named after Prof. R. Uma Shaanker, Founder Trustee of Ashoka Trust for Research in Ecology and the Environment (ATREE), Bangalore, India. He has contributed immensely to the understanding of ecology, evolution, and conservation of flora and fauna of the Western Ghats, India.

Type material examined

Holotype

INDIA – Mizoram • empty shell (D: 2.7 mm, H: 2 mm, Fig. 73); Blue Mountain, Lawngtlai district ; 22.727° N, 93.135° E; 1400 m a.s.l.; 27 Jan. 2019; N.A. Aravind leg.; Ar 73; NZSI LM1742 View Materials . GoogleMaps

Paratypes

INDIA – Mizoram • 28 empty shells; same data as for holotype; NZSI LM1743 View Materials GoogleMaps • 2 empty shells; same data as for holotype; Ar 58; NZSI LM1744 View Materials GoogleMaps • 1 empty shell; same data as for holotype; Ar 75; NZSI LM1907 View Materials GoogleMaps • 3 empty shells; same data as for holotype; Ar 40; NZSI LM1745 View Materials GoogleMaps • 1 empty shell; same data as for holotype; Ar 50; NZSI LM1746 View Materials GoogleMaps • 3 empty shells; same data as for holotype; Ar 63; NZSI LM1747 View Materials GoogleMaps • 1 empty shell; same data as for holotype; Ar 25; NZSI LM1748 View Materials GoogleMaps • 1 empty shell; same data as for holotype; Ar 24; NZSI LM1749 View Materials GoogleMaps • 1 empty shell; same data as for holotype; Ar 15; NZSI LM1750 View Materials GoogleMaps • 1 empty shell; same data as for holotype; Ar 15; NZSI LM1908 View Materials GoogleMaps .

Additional material examined

INDIA – Mizoram • 2 juvenile empty shell ( Fig. 65D–F, 66C–D); same data as for holotype; NZSI LM1751 View Materials GoogleMaps • 1 broken shell; same data as for holotype; Ar 21, NZSI LM1752 View Materials GoogleMaps • 3 corroded/broken shells; same data as for holotype; Ar 36, NZSI LM1753 View Materials GoogleMaps .

Description

Shell small, light yellowish to orange or ochre, in some specimens with reddish apex; glossy, semitranslucent; shell outline slightly oval in dorsal view; spire slightly elevated, low conical; body whorl rounded; protoconch low, glossy, consisting of 1.25–1.5 whorls; R1 of ca 1.5 whorls, glossy, nearly smooth, with some inconspicuous, dense, low riblets, in some specimens ribs increase in strength on the last ca quarter whorl; spiral striation absent; boundary between R1 and R2 conspicuous due to the sudden change to a regularly, densely ribbed surface; R2 with ca 18–22 straight, sharp, lamella-like ribs; R2 ribs low, blunt, curved towards aperture, spaces between the ribs are approximately the width of a single rib; cross sectional view of R2 was examined in a specimen ( Fig. 66C–D): anterior crust forms a significantly elevated rib, which has an anterior projection (i.e., the R2 ribs are curved towards the aperture); anterior crust folds over the much weaker posterior crust; microtunnel wide compared to ribs, its cross sectional view teardrop-shaped; R2+R3 ca 150 degrees; R3 slightly longer than R2; boundary between R2 and R3 clearly visible due to a deep constriction; R3 forms a blunt tip towards constriction and possesses two swellings; the upper swelling is visible only on the dorsal side, stops at the centre of the whorl, while the lower swelling (i.e., the one situated closer to the aperture) reaches the ventral side of shell; the dent separating the two swellings is elongated, beginning at the suture; aperture strongly oblique to shell axis, rounded with a very slight upper (parieto-palatal) incision; boundary between inner and outer peristomes conspicuous; inner peristome slightly thickened, protruding; outer peristome more conspicuous, sharp, strongly expanded, and reflected towards umbilicus; umbilicus very narrow, ca 1/5 –1/6 of shell width, elongated, oval.

OPERCULUM. Outer surface multispiral, without elevated lamina, inner side with an elevated, flat-topped nipple.

MEASUREMENTS. D: 2.6–3.1 mm, H: 2–2.2 mm.

Distribution

Known only from the Blue Mountain region.

Differential diagnosis

Dicharax akhaensis is similar in having two swellings and being glossy, but differs from the new species by having more widely-spaced R1 ribs, denser R2 ribs (and possibly lower, although the holotype is corroded), a fringed aperture, and a wider umbilicus.

Dicharax birugosus is similar in colour, size, sculpture and length of R1 and R2, but its R3 is shorter than that of the new species, the aperture is slightly fringed and has a deep basal incision. Moreover, the two swellings are arranged differently: the main swelling is oblique to the constriction in Dicharax birugosus , and rather parallel in the new species, while the area on which the secondary swelling is situated is much wider in the new species.

Dicharax subculmen belongs to the “Elephant Dicharax ” species group but is somewhat similar to this new species, at least in dorsal view. Nevertheless, the new species has a more depressed shell and a wider umbilicus, a deeper ditch between the primary and secondary R3 swellings, a longer R3 with a larger distance between the peristome and the secondary swelling, and a thinner peristome.

Dicharax kurzianus has a fringed aperture.

Dicharax multirugosus has a more depressed shell, and has three separate R3 swellings.