Santanusus malabaricus ( Henderson, 1912 ), 2025

Santanusus malabaricus ( Henderson, 1912) comb. nov.

[Santanu’s forest crab]

( Figs. 22–24 View FIGURE 22 View FIGURE 23 View FIGURE 24 )

Paratelphusa (Liotelphusa) malabarica Henderson, 1912: 111 View in CoL .

Paratelphusa malabarica View in CoL – Henderson 1913: 47 (list).

Travancoriana malabarica – Bott 1970b: 42, pl. 5 figs. 45–47, pl. 26 fig. 22 (part).— Srivastava 2009: 29 (list).

Vanni malabarica View in CoL – Bahir & Yeo 2007: 340, figs. 33, 34.— Klaus et al. 2014: table S1 (list).—Pati et al. 2014: 659, pl. 2 figs. 4–6, pl. 4 figs. 1, 2; 2019b: 14, pl. 1 fig. 5.— Rajesh et al. 2017: 146, fig. 29.—Pati 2020: 162 (list).— Pati & Pradhan 2020: 555836 (list).

Not Paratelphusa (Barytelphusa) travancorica View in CoL – Roux 1931: 53.

Not Travancoriana travancorica – Bott 1970a: 336.

Type material. Lectotype: male ( CW 13.6 mm, CL 10.1 mm) ( NHM 1913.2.11.1), India, Kerala State, “Cochin State Forest” [Thrissur District, Cochin State Forest, stream near Kavalai ], [ca. 10.387° N, 76.555° E], “elev. ca. 305 m a.s.l. ”, presented by J. R. Henderson, “ October 2011 ”. GoogleMaps

Other type material examined. Paralectotypes: male ( CW 18.0 mm, CL 13.2 mm, FW 6.9 mm, CH 8.3 mm), 2 females ( CW 18.5–21.6 mm, CL 14.4–16.2 mm; smaller female FW 7.2 mm, CH 8.6 mm) ( ZSIK 7936 /10), same collection data as for lectotype, coll. J. R. Henderson GoogleMaps .

Other material examined. India – Kerala State: male ( CW 14.4 mm, CL 10.9 mm, CH 6.6 mm, FW 5.4 mm) ( ZSI-WGRC IR/INV/10509) , Kozhikode District, Kakkavayal , 11.493° N, 75.974° E, elev. 50 m a.s.l., coll. P. Girish Kumar, 8 January 2018 GoogleMaps .

Diagnosis. As for new genus.

Remarks. Henderson (1912) obtained nine males and eleven females and mentioned in the original publication that “the type ( Crustacea Reg. No. 7936/10) is preserved in the Indian Museum”.Although he discussed the deposition of type specimens in the Indian Museum (= ZSIK), he did not specify their exact number. The present investigation, however, recovered only one male and two females as the types, with the catalogue number ZSIK 7936/10. The other two type specimens (male and female) were already presented to the NHM, likely by J.R. Henderson, and the male syntype (“MLo 1913-2-11-1-2 ” [NHM 1913.2.11.1]) was listed by Bott (1970b). The male syntype (NHM 1913.2.11.1) was designated as the lectotype by Bahir & Yeo (2007), which was supposedly examined by Bott (1970b) as stated in Bahir & Yeo (2007). Bott (1970b: pl. 5 figs. 45–47, pl. 26 fig. 22), however, illustrated a nontype male (from MHNG) of V. malabarica from the Aliyar River, Anamalai. In the species account, however, Bott (1970b) cited “MBa 798a” [NMB 798a] for a specimen from the Aliyar River; he also cited a juvenile male (“MBa 798b” [NMB 798b]) from the Naduar River. These specimens of V. malabarica from Aliyar and/or Naduar rivers were previously identified by Roux (1931) as Paratelphusa (Barytelphusa) travancorica and by Bott (1970a) as Travancoriana travancorica . The same juvenile male (NMB 798b) from the Naduar River again appeared in the phylogenetic study of Klaus et al. (2014) under the name, Vanni malabarica . The specimens from the Aliyar and Naduar rivers and adjoining areas of the Coimbatore district of Tamil Nadu are those of S. malabaricus comb. nov., not V. travancorica .

The type locality of S. malabaricus comb. nov. is the Cochin State Forest, and the types were collected from a stream near Kavalai, which was reported to be at an elevation of about 1000 feet (305 m a.s.l.) (see Henderson 1912). Pati et al. (2014) and Rajesh et al. (2017) mentioned that the type locality falls in “ Kochi ” [Ernakulam] and Palakkad districts, respectively. There was a tramway in the Cochin State Forest, which had been in operation during 1907-1963 between Parambikulam of Palakkad district and Chalakudy of Thrissur district, with Kavalai as a transitional location ( Vimal Kumar 2019). The approximate geographic coordinates (10.387° N, 76.555° E) of the stream near Kavalai are now traced based on the elevation data provided by Henderson (1912). The stream near Kavalai actually falls in the Thrissur district of Kerala.

Ecological notes. Santanusus malabaricus comb. nov. was found to be living underneath stones at the edge of a stream, preferring relatively dry zones, with few individuals actually observed in the water ( Henderson 1912). Rajesh et al. (2017) reported that their collection of specimens included those found underneath the stones of a small stream, as well as larger individuals that inhabited the areas between plant roots along the banks of fast-flowing streams.

Geographical distribution. As for new genus.

Genus Pusillosa gen. nov.

( Figs. 25 View FIGURE 25 , 26 View FIGURE 26 )

Type species. Paratelphusa (Liotelphusa) pusilla Roux, 1931 View in CoL , by present designation; gender of genus feminine. Diagnosis. Small sized crabs (maximum CW 12.9 mm). Carapace relatively broad (CW/CL = ca. 1.2–1.4), relatively low ( CH /CW = ca. 0.4), with moderately convex lateral margins; frontal medial triangle incomplete, lateral margins indiscernible; postorbital cristae weakly developed posterolaterally, not reaching lateral margins of carapace; external orbital angle broadly triangular, with long outer margin, ca. 4 times length of inner margin; epibranchial tooth low, located at same level of postorbital cristae; epistome posterior margin with well-developed, triangular medial tooth and sinuous lateral lobes ( Fig. 25A–C View FIGURE 25 ; see Roux 1931: fig. 16; Bahir & Yeo 2007: figs. 37A, 38A, B). Maxilliped 3 with well-developed flagellum on exopod ( Fig. 25F View FIGURE 25 ). Chelipeds relatively slender in adult males ( Fig. 25A, G View FIGURE 25 ; see Roux 1931: fig. 16). Ambulatory legs relatively slender, longer, setose ( Fig. 25A, H View FIGURE 25 ; see Roux 1931: fig. 16). Male s2/s3 and s3/s4 indiscernible ( Fig. 25D View FIGURE 25 ; see Bahir & Yeo 2007: figs. 37B, 38C). Male sternopleonal cavity relatively short, reaching to imaginary line joining anterior part of cheliped coxae ( Fig. 25D View FIGURE 25 ; see Bahir & Yeo 2007: figs. 37B, 38C). Male pleon relatively broad, with strongly concave, rather angular lateral margins; pleonal somite 6 trapezoidal, relatively broad, proximal width ca. 1.5 times medial length ( Fig. 25D, I View FIGURE 25 ; see Roux 1931: fig. 17; Bahir & Yeo 2007: figs. 37C, 38C). G1 relatively stout; ultimate article conical, relatively slender, relatively short, ca. 0.4 times length of penultimate article; penultimate article stout ( Fig. 26A, B View FIGURE 26 ; see Bahir & Yeo 2007: fig. 37D, E). G2 longer than G1, ca. 1.2 times G1 length; ultimate article long, ca. 0.4 times length of penultimate article ( Fig. 26C View FIGURE 26 ). Vulvae relatively widely located from each other (VD/SW = ca. 0.2) ( Fig. 25J View FIGURE 25 ).

Etymology. The genus name is an arbitrary combination of ‘ pusillus ’ (Latin for very small) and the genus name Thelphusa , which alludes to the very small size of the crabs. The gender of this genus is feminine.

Remarks. Pusillosa gen. nov. can be set apart from Vanni s. str. by the very small size of the crabs and the characters in postorbital cristae, external orbital angle, ambulatory legs, male s2/s3, male pleon, and G1 (see Remarks for Vanni ). This new genus currently includes the lone species, Pu. pusilla ( Roux, 1931) comb. nov.

Pusillosa gen. nov. can be recognised from the gecarcinucid genera of southern India mainly by the relatively low carapace ( CH /CW = ca. 0.4), with moderately convex lateral margins ( Fig. 25A–C View FIGURE 25 ; see Roux 1931: fig. 16; Bahir & Yeo 2007: figs. 37A, 38A, B); the weakly developed postorbital cristae ( Fig. 25A, B View FIGURE 25 ; see Roux 1931: fig. 16; Bahir & Yeo 2007: figs. 37A, 38A); the broadly triangular external orbital angle, with outer margin long, ca. 4 times the inner margin length ( Fig. 25A, B View FIGURE 25 ; see Roux 1931: fig. 16; Bahir & Yeo 2007: figs. 37A, 38A); the low epibranchial tooth ( Fig. 25A, B View FIGURE 25 ; see Roux 1931: fig. 16; Bahir & Yeo 2007: figs. 37A, 38A); the distinct flagellum on the exopod of maxilliped 3 ( Fig. 25F View FIGURE 25 ); the relatively slender pereiopods, with the ambulatory legs being longer and setose ( Fig. 25A, G, H View FIGURE 25 ; see Roux 1931: fig. 16); the indiscernible male s2/s3 and s3/s4 ( Fig. 25D View FIGURE 25 ; see Bahir & Yeo 2007: figs. 37B, 38C); the strongly concave lateral margins of the male pleon, appearing rather angular ( Fig. 25D, I View FIGURE 25 ; see Roux 1931: fig. 17; Bahir & Yeo 2007: figs. 37C, 38C); the relatively stout G1, with the conical and relatively short ultimate article (ca. 0.4 times the length of the penultimate article), and the relatively stouter penultimate article ( Fig. 26A, B View FIGURE 26 ; see Bahir & Yeo 2007: fig. 37D, E); and the longer G2 than G1 ( Fig. 26 View FIGURE 26 ).

Geographical distribution. Pusillosa gen. nov. is endemic to the central Western Ghats and known only from the higher elevations (2100–2315 m a.s.l.) of Nilgiris district in Tamil Nadu, southern India ( Roux 1931; Bott 1970a, 1970b; Bahir & Yeo 2007; present study) ( Fig. 1B View FIGURE 1 ).