Acanthopotamon fungosum (Alcock, 1909)

1909. Potamon (Paratelphusa) fungosum Alcock, Rec. Indian Mus., 3 (3): 250.

2019. Acathopotamon fungosum: Pati and Thackeray, Zootaxa, 4440 (1): 9.

Material examined: 1♂ (CW 21.6 mm, CL 16.6 mm, CH 9.6 mm, FW 7.6 mm), Arunachal Pradesh, East Siang district, small hill stream connected to Sibyia River, near Siluk village, ca. 30 km north east of Pasighat (28.175°N, 95.470°E), altitude 336 mASL, 4-xi-2019, coll. S. Mitra (ZSI-C. 8252/2) .

Material compared: Acathopotamon fungosum: Lectotype ♂ (ZSIK 6611-6624 /9), India: Assam, Cachar, Darband pass, coll. J. Wood-Mason; Paralectotype 1 ♂ and 1 ♀ (ZSIC 6611-6624 /9), data same as Lectotype; 1 ♂ and 2 ♀ (ZSIC 5540 /10), India: Assam, Cachar, coll. E.B. Baker.

Diagnosis: Carapace sub-hexagonal, slightly broader than long, convex, covered by short spongy fur, carapace dorsal surface broadly corrugated and lumpy, much pitted when denuded; cervical groove only demarcated in mesogastric area, otherwise its superficial; epigastric cristae broad, blunt; well advance of postorbital cristae; post orbital cristae short, not confluent with first epibranchial tooth; external orbital tooth broadly triangular; anterolateral margin gently convex, with 4 epibranchial teeth, first epibranchial tooth broadly triangular, rests are sharp (Figure 8A); third maxilliped ischium elongately rectangular with distinct longitudinal median sulcus; exopod not distally tapered, with well developed flagellum, longer than merus width; carpus and merus of cheliped with distinct subdistal and subterminal spine; ambulatory legs covered with short and long velvety setae; suture between thoracic sternites 2 and 3 distinct, eighth thoracic sternites possesses a transverse ridge at the suture between thoracic sternites 7 and 8 interrupting the longitudinal median line; Sterno-pleonal cavity reaching imaginary line joining beyond the anterior edge of cheliped bases; male pleon broadly triangular; G1 terminal article outwardly curved, long, slender, sub cylindrical, tapering towards tip, covered by short setae (Figure 8B, C); G2 distal part is distinctly longer than half of the basal part (Figure 8 D); female vulvae located on the middle of 6 th sternites, opening large, longitudinally oval.

Distribution: INDIA: Arunachal Pradesh (Present record), Assam and Mizoram (Pati et al., 2019).

Remarks: Acanthopotamon fungosum was descried from Cachar, Assam (Alcock, 1909), having a patchy distribution range in Northeast India. Shallow streams or a Rocky River bed is the suitable habitat for this species. The present report forms its first record from Arunachal Pradesh and extension of its distributional range further northeast.