Badistemon pealianus ( Wood-Mason, 1871 ) Mitra & Monica & Waikhom, 2020

Mitra, Santanu, Monica, Thingbaijiam & Waikhom, Mema Devi, 2020, A new species of freshwater crab of the genus Badistemon Yeo & Ng, 2007 (Decapoda: Brachyura: Potamidae: Potamiscinae) from Manipur State, India with the reassignment of Potamiscus pealianus (Wood-mason, 1871), Zootaxa 4838 (4), pp. 475-490 : 483-489

Badistemon pealianus ( Wood-Mason, 1871) comb. nov.

( Fig. 7 A–C, 8D–F)

Telphusa pealiana Wood-Mason, 1871:204 , pl. 14, fig.7–11.

Potamon pealianum —De Man, 1898: 410, pl. 5, fig. 7 [not Telphusa pealiana Wood-Mason, 1871 ].

Potamon (Potamon) pealianus —Rathbun, 1904:310. [not Telphusa pealiana Wood-Mason, 1871 ]

Potamon (Potamon) pealianum antennarium Alcock, 1909: 245 .

Potamon (Potamon) pealianum —Alcock, 2010:38, pl.10, fig. 44.

Potamiscus pealianus — Bott, 1970:161, pl. 38, fig. 33; pl. 47, fig. 29.

Potamiscus pealianus — Brandis, 2000: 72, pl. 7 a–c. [not Telphusa pealiana Wood-Mason, 1871 ]

Potamiscus pealianus —Ng et al., 2008: 165 [list only]

Remarks. Wood-Mason (1871) described Telphusa pealiana (1871: 204, pl. XIV. Fig. 7 –11) based on a single male specimen (cw 41mm, cl 32 mm), collected by S. E. Peal, from Sibsagar, Assam. Alcock (1910) classified some species of Potamiscus (sensu. lato), namely P. pealianum ; P. paelianum var. antennarium ; P. tudrgidulum and P. tumidum ; in a separate ‘group’ named as “ pealianum ”- group, in having some common characters i.e., grooves and regions distinct, cervical groove cuts the post orbital cristae at the same point, carapace deep, and convex longitudinally. Alcock (1910: 40, fig.44) examined a good series of collections, in ZSI, Kolkata, collected by S.E. Peal, from Sivasagar, Assam; but unfortunately did not referred to the type specimens in those collections. Later, Bott (1970) synonymised Potamon (Potamon) pealianum var. antennarium, Alcock, 1909 , with P. pealianus and transferred this species to Potamiscus Alcock, 1909 ; by designating a male lectotype (cw 41.6 mm, cl 35.2 mm) and a female paralectotype (ZSI-C6413/3), from the collections of S. E. Peal (collected from Sibsagar, Assam). While examining all the Potamon (Potamon) pealianum , identified by Alcock (1910), we found out that the male specimen (cw 41.6 mm, cl 35.2 mm, ch 18.8 mm, fw 10.4 mm)(ZSI-C 6958/3) is agrees well with the original descriptions of Wood-Mason (1871), which is therefore the holotype; simultaneously all the other specimens, collected by S.E. Peal from Sivasagar, Assam, should be considered as paratypes. Bott’s (1970) decision, regarding subsequent designation of lectotype and paralectotype, however, is invalid. Potamiscus pealianus s.lato is easily distinguished from Potamiscus s. stricto [type species: Potamon (Potamiscus) annandali Alcock, 1909 ], by its more broad, squarish carapace ( Alcock, 1910: pl 10. fig. 44; Fig. 7 A ) (vs. relatively narrow carapace in Potamiscus ; Alcock, 1910: pl. 3. Fig. 10 ; Naruse et al., 2018: fig. 28 a; Yeo & Ng, 2007: fig. 11 a); weakly developed and distinctly rugose postorbital cristae ( Alcock, 1910: pl 10. fig. 44; Fig. 7 A ) (vs. well developed and distinctly non-rugose, cristate postorbital cristae in Potamiscus ; Alcock, 1910: pl. 3. Fig. 10 ; Naruse et al., 2018: fig. 28 a; Yeo & Ng, 2007: fig. 11 a); antennular fossae relatively broad, sub triangular ( Fig. 7B ) (vs. narrow, slit-like antennular fossae; Naruse et al., 2018: fig. 28 b; Yeo & Ng, 2007: fig. 11 b); relatively longer and slender propodus and dactylus of ambulatory legs, lined with short, stiff setae ( Alcock, 1910: pl 10. fig. 44) (vs. relatively shorter propodus and dactylus, glabrous ambulatory legs in Potamiscus ; Alcock, 1910: pl. 3. Fig. 10 ; Naruse et al., 2018: fig. 28 a); and the exopod of third maxilliped with well-developed flagellum (vs. flagellum absent or vestigial in third maxilliped exopod) ( Naruse et al. 2018).

We examined the old collections of S.E. Peal from Sibsagar, Assam and Kakhyen hills of Myanmar (collected by J. Anderson) along with the holotype and a recent collections from Mizoram ( Mitra, 2017), and found that P. pealianus is congeneric with B. turgidulum and B. fulvum sp. nov. All these species has same squarish-looking, relatively high and longitudinally convex carapace; exopod of third maxilliped with well-developed flagellum, not exceeding the merus width; male sternopleonal cavity reaches imaginary line of posterior border of the cheliped coxae; G1 relatively long, subcylindrical, with short and low dorsal flap. As such we herein re-assign Potamiscus pealianus ( Wood-Mason, 1871) as Badistemon pealianus n. comb. The genus Badistemon now consists of three species, a key to the species are provided here for easy identification.

Figures

FIGURE 7. Badistemon pealianus (Wood-Mason, 1871), comb. nov. holotype male (ZSI-C 6958/3) (cw 41.6 mm × cl 35.2 mm): A. dorsal view of carapace; B. frontal view of cephalothorax; C. male thoracic sternum and pleon.

FIGURE 10. Badistemon fulvum n.sp., holotype male (ZSI-C7543/2) (cw 48.7 mm × cl 39.5 mm): A, live coloration; B, habitat in the type locality, Bungkucha stream; C, burrow