Dicharax ganeshaiahi Páll-Gergely & Aravind, 2025

Dicharax ganeshaiahi Páll-Gergely & Aravind sp. nov.

urn:lsid:zoobank.org:act:

Figs 64, 65A–C, 66A–B

Diagnosis

A small species of Dicharax with a glossy shell, smooth, short R2 (combined length of R2+R3 ca quarter whorl, R3 ca twice as long as R2), an R3 with a central, blunt swelling, a rounded aperture with shallow upper and lower incisions, and a strongly expanded outer peristome.

Etymology

This species is named after Prof. K.N. Ganeshaiah, Founder, Trustee of Ashoka Trust for Research in Ecology and the Environment (ATREE), Bangalore, India. He has contributed immensely to the understanding of the ecology, evolution, and conservation of Indian flora and fauna. He is also a popular science communicator in the vernacular language and has published over 32 books in the Kannada language.

Type material examined

Holotype

INDIA – Mizoram • empty shell (D: 3.2 mm, H: 2.3 mm, Fig. 64); Blue Mountain, Lawngtlai district ; 22.727° N, 93.135° E; 1400 m a.s.l.; 27 Jan. 2019; N.A. Aravind leg.; Ar 62; NZSI LM1755 View Materials . GoogleMaps

Paratypes

INDIA – Mizoram • 8 empty shells; Blue Mountain, Lawngtlai district ; 22.727° N, 93.135° E; 1400 m a.s.l.; 27 Jan. 2019; N.A. Aravind leg.; Ar 62; NZSI LM1756 View Materials GoogleMaps • 2 empty shells; same data as for preceding; Ar 47; NZSI LM1757 View Materials GoogleMaps • 1 empty shell ( Fig. 65A–C, 66A–B); same data as for preceding; Ar 27; NZSI LM1758 View Materials GoogleMaps • 6 empty shells; same data as for preceding; Ar 72; NZSI LM1759 View Materials GoogleMaps .

Additional material examined

INDIA – Mizoram • 1 corroded empty shell; same data as for holotype; Ar 47; NZSI LM1760 View Materials GoogleMaps • 6 corroded empty shells; same data as for holotype; Ar 72; NZSI LM1761 View Materials GoogleMaps .

Description

Shell small, yellowish or pinkish when fresh, semitranslucent; entire shell surface glossy; shell outline rounded in dorsal view, R2 and end of R3 conspicuously swollen, although not in all specimens; spire elevated, conical; body whorl rounded; protoconch low, smooth, consisting of 1.25–1.5 whorls; R1 of ca 1.5–1.75 whorls, smooth, glossy, last ca quarter whorl of some specimens with weak, widely-spaced ribs, while in other specimens entire R3 remains smooth; some weak ribs of the last ca quarter whorl visible inside umbilicus; boundary between R1 and R2 not conspicuous, in the case of specimens with ribbed end of R1 the change between the two regions is more clearly visible due to the large increase in rib density; R2 without elevated ribs, but very densely arranged lighter and darker alternating stripes (more than 40 in number); cross sectional view of R2 was examined in a specimen ( Fig. 66C–D): anterior crust forms no rib, it is entirely flat; instead of folding over the posterior crust, the posterior crust covers the larger part of the microtunnels, and the anterior crust only covers the edge of the posterior crust; microtunnel wide compared to anterior and posterior crusts, its cross sectional view teardrop-shaped; R2+R3 ca 90 degrees; R3 ca twice as long as R2; boundary between R2 and R3 clearly visible due to a shallow constriction; R3 with a low, central, triangular swelling; aperture strongly oblique to shell axis, rounded with a shallow upper (parieto-palatal), and a shallow lower (basal) incision; inner and outer peristomes clearly separated (mostly at the parietal, palatal and columellar part and less so at the basal part); inner peristome slightly protruding; outer peristome strongly expanded and reflected; umbilicus ca one fourth of shell width, almost rounded, although its part facing R2 is nearly straight, forming a slight keel on the umbilical side of R2.

OPERCULUM. Inner side smooth, without central nipple; outer side smooth, without any sculpture (Ar27).

MEASUREMENTS. D: 2.8–3.4 mm, H: 2.1–2.4 mm.

Differential diagnosis

Dicharax dalingensis ( Fig. 62A–E) is similar in having a smooth R2, but has longer R2 and R3, and a higher spire.

Dicharax lenticulus ( Fig. 63) also has a smooth R2, but is much larger, and has a longer R2 and R3. Moreover, both D. dalingensis and D. lenticulus have an incision between the penultimate whorl and peristome, while the peristome is attached to the penultimate whorl in the new species.

Dicharax pachitaensis ( Fig. 61K–O), which is probably the most similar species, also has a smooth R2, but the combined length of R2 and R3 is usually (not always) longer than that of the new species. Moreover, D. pachitaensis has prominent ribs near the suture on the dorsal side, the R3 swelling is situated a greater distance from the peristome, and its aperture has deeper upper and lower incisions.

Remarks

The cross-sectional view of R2 of two species of Alycaeinae with smooth R2 is known: Dicharax moellendorffi (Kobelt & Möllendorff, 1886) (see Páll-Gergely et al. 2017) and Metalycaeus minatoi Páll-Gergely, 2017 (see Páll-Gergely & Asami 2017). Even though the R2 surfaces are similar, the fine structure of the R2 (i.e., how the anterior and posterior crusts fold over each other to make the microtunnels) is very different. In the case of D. moellendorffi , the anterior crust has a strong posterior projection that covers the anterior crust. In the case of Metalycaeus minatoi , the anterior and posterior crusts meet just above the microtunnel, and in the new species the posterior crust has an elongated anterior projection covering the microtunnel.