Dicharax theobaldi (W.T. Blanford, 1862)

Fig. 69F–J

Alycaeus Theobaldi W.T. Blanford, 1862: 142–143 .

Alycaeus theobaldi var. diyungensis Godwin-Austen, 1914: 401–402, pl. 138 fig. 4. Syn. nov.

Alycaeus maosmaiensis Godwin-Austen, 1922: 365, text figs. Syn. nov.

Alycaeus theobaldi – Sowerby 1877: pl. 5, species 44. — Godwin-Austen 1914: 359–360, pl. 149 figs 3, 3a–b; 1914: 382–383, pl. 145 figs 4, 4a.

Alycaeus (Dicharax) theobaldi – Kobelt 1902: 377–378. — Gude 1921: 272–273.

Chamalycaeus (Dicharax) theobaldi – Ramakrishna et al. 2010: 67.

Dicharax maosmaiensis – Páll-Gergely et al. 2020: 67.

Dicharax theobaldi – Páll-Gergely et al. 2020: 73.

Dicharax theobaldi diyungensis – Páll-Gergely et al. 2020: 73.

Diagnosis

The combination of the strong, widely-spaced R1 ribs, the relatively widely-spaced R2 ribs and the blunt, central R3 swelling distinguish this species from its congeners.

Type material examined

INDIA • 1 syntype of A. theobaldi (Fig. 69F–J); Khasi Hills, NHMUK 1906.4.4.60 • 12 syntypes of Alycaeus theobaldi var. diyungensis (Fig. 69F–J); Diyung Valley, N of Asalu; NHMUK 1903.7.1.2546 • 1 syntype of A. maosmaiensis (Fig. 69K–O) separated in a vial with pink wool + 4 additional syntypes; Maosmai, nr Cherrapoonjee, Khasi; NHMUK 20191067 .

Additional material examined

INDIA • 3 shells; Nongphrian, Khasi Hills; Dr Alfred Oberwimmer coll.; NHMW (mixed sample with D. hebes) • 1 shell; same data as for preceding; NHMW 14715 (mixed sample with D. hebes) .

Type localities

“in montibus Khasi” ( A. theobaldi); “Diyung Valley, north of Asalu, N. Cachar” ( A. theobaldi var. diyungensis); “Khasi Hills, near Cherrapunji, at the mouth of the Maosmai cave” ( A. maosmaiensis).

Remarks

According to the original description of Alycaeus theobaldi var. diyungensis, that variety differs from the typical A. theobaldi in the following traits: “This Diyung Valley species is a departure from A. theobaldi of the Khasi Hills in having the apex less high and conical, the suture more impressed, the shell more openly umbilicated; costulation next suture stronger” (Godwin-Austen 1914: 402). However, we do not see any of these differences comparing the type specimens of the two taxa. Therefore, we treat D. theobaldi diyungensis as a junior synonym of D. theobaldi .

The type specimens of D. theobaldi, D. theobaldi diyungensis and D. maosmaiensis are similar in shell size and shell shape, while the sculpture of R1 shows differences. Namely, D. theobaldi and D. theobaldi diyungensis have strong, widely-spaced ribs that are more or less regular at the beginning of R1, and become irregular and more widely-spaced towards its end, while D. maosmaiensis has a smooth beginning of R1, and at the end of R1 the ribs are relatively weak, and slightly denser than in the other two nominal taxa. Nevertheless, these differences are considered part of the intraspecific variability. A similar case (intraspecific variability in R1 rib density) was shown in the case of Dicharax notus (see Páll-Gergely et al. 2021).