Pusillosa pusilla ( Roux, 1931 ), 2025

Pusillosa pusilla ( Roux, 1931) comb. nov.

[Tiny Nilgiri crab]

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

Paratelphusa (Liotelphusa) pusilla Roux, 1931: 58 View in CoL , figs. 16, 17.

Gubernatoriana pusilla – Bott 1970a: 336: 1970b: 46, pl. 6 figs. 57–59, pl. 27 fig. 26.— Srivastava 2009: 29 (list).

Vanni pusilla View in CoL – Bahir & Yeo 2007: 342, figs. 37, 38.—Pati 2020: 162 (list).— Pati & Pradhan 2020: 555836 (list).— Sruthi & Thirunavukkarasu 2022: 461 (list).

Type material. Lectotype (designated herein based on illustrations of Bahir & Yeo (2007: figs. 37, 38)): male ( CW 12.0 mm, CL 8.4 mm) ( NMB 801 View Materials a), India, Tamil Nadu State, Nilgiris District, Nilgiris, Avalanche , 11.315° N, 76.599° E, “elev. 2100 m a.s.l. ”, coll. J. Carl, 18 January 1927. GoogleMaps

Other material examined. India– Tamil Nadu State: 4 males ( CW 3.9–9.3 mm, CL 3.2–6.9 mm, CH 1.3–3.7 mm, FW 1.5–3.2 mm), 2 females ( CW 8.2–8.3 mm, CL 6.4–6.5 mm, CH 3.3–3.4 mm, FW 3.1 mm each) ( ZSI-WRC C.2343), Nilgiris District , Nilgiris, Mukurthi Range, hill stream near earthen dam, 11.259° N, 76.526° E, elev. 2276 m a.s.l., coll. R. Babu et al., 14 February 2023 GoogleMaps ; 4 males ( CW 9.1–10.1 mm, CL 6.8–7.6 mm, CH 3.6–4.0 mm, FW 3.1–3.5 mm) ( ZSI-WRC C.2342), Nilgiris District , Nilgiris , on the way to Mukurthi Peak, Mukurthi Forest hill stream, 11.391° N, 76.518° E, elev. 2315 m a.s.l., coll. R. Babu et al., 12 February 2023 GoogleMaps .

Diagnosis. As for new genus.

Colour in life. The live colouration of the species was formerly not known. Pusillosa pusilla comb. nov. exhibits a deep purple colour of the carapace and pereiopods, with the ventral surface relatively paler and the chelipeds red-violet ventrally (https://www.inaturalist.org/observations/190552893).

Remarks. Bott (1970a, 1970b) assigned Paratelphusa (Liotelphusa) pusilla Roux, 1931 , to Gubernatoriana without any indications, because he had limited material. Roux (1931) originally examined four females and two males. Bott (1970b) also mentioned the same number and gender of specimens, but one male and three females were from the MHNG without catalogue number, and one male and one female from the NMB with catalogue number NMB 801a. Bott (1970b) also designated the male from the MHNG as the lectotype (also see Bott 1970a). On the contrary, he illustrated the male from NMB ( Bott 1970b: pl. 6, figs. 57–59) and mentioned it as the lectotype. The lectotype designation by Bott (1970a, 1970b) is, therefore, not clear. This discrepancy was also noted by Bahir & Yeo (2007) while assigning the species to Vanni , who specifically stated that Bott (1970b) supposedly designated the NMB male specimen as the lectotype, and the MHNG male specimen appeared as the lectotype in the text due to a typographical error. Bahir & Yeo (2007), therefore, continued to provisionally regard the NMB male specimen as the paralectotype. Since Bott (1970a, 1970b) could not unambiguously select a particular syntype that acts as a unique name-bearing type as necessary according to Article 74.5 of the International Code of the Zoological Nomenclature ( ICZN 1999), and Bahir & Yeo (2007) did not clearly identify a lectotype, the male specimen (12.0 × 8.4 mm) (NMB 801a) illustrated by Bahir & Yeo (2007: figs. 37, 38) is hereby designated as the lectotype for the nomenclatural stability of Pusillosa pusilla ( Roux, 1931) comb. nov. The present designation of the lectotype based on illustrations is code-compliant as per Article 74.4 ( ICZN 1999).

Pusillosa pusilla comb. nov. is likely to be confused with eye-catching, coloured small freshwater crabs, e.g.,most species of Ghatiana Pati & Sharma, 2014 , Gubernatoriana Bott, 1970 , Inglethelphusa Bott, 1970 , and Sahyadriana Pati & Thackeray, 2018 . The species of Ghatiana , Gubernatoriana , Inglethelphusa , and Sahyadriana possess some morphological characters in common with those of Pu. pusilla comb. nov., for instance, the indiscernible or weakly developed postorbital cristae, the low epibranchial tooth, the setose ambulatory legs, and the indiscernible male s2/s3 and s3/s4 (cf. Pati & Thackeray 2018, 2021; Pati et al. 2022b, 2023c, 2024). These morphological similarities could have confused Bott (1970a, 1970b) in assigning the species to Gubernatoriana . Pusillosa pusilla comb. nov. need not be confused with any of the species of Ghatiana , Gubernatoriana , Inglethelphusa , and Sahyadriana because it possesses the well-developed flagellum on the maxilliped 3 exopod ( Fig. 25F View FIGURE 25 ) (versus maxilliped 3 exopod completely lacking a flagellum; see Pati & Thackeray 2018, 2021; Pati et al. 2022b, 2023c, 2024), and the distinctly longer G2, ca. 1.2 times the G1 length, with a long ultimate article, ca. 0.4 times the length of the penultimate article ( Fig. 26 View FIGURE 26 ) (versus G2 and its ultimate article conspicuously short; Pati & Thackeray 2018, 2021; Pati et al. 2022b, 2023c, 2024).

Ecological notes. Pusillosa pusilla comb. nov. is a high mountain dweller, living at elevations of 2100–2315 m a.s.l. ( Roux 1931; present study). The recent specimens were collected underneath small stones at the margins of shallow and slow-flowing streams and adjacent areas.

Geographical distribution. As for new genus.

Genus Nilgiriana gen. nov.

( Figs. 27–29 View FIGURE 27 View FIGURE 28 View FIGURE 29 , 30A View FIGURE 30 )

Type species. Paratelphusa (Liotelphusa) nilgiriensis Roux, 1931 View in CoL , by present designation; gender of genus feminine.

Diagnosis. Medium sized crabs (maximum CW 24.7 mm). Carapace relatively broad (CW/CL = ca. 1.3–1.5), 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. 4–5 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 gently to strongly sinuous lateral lobes ( Figs. 27A–C, E–G View FIGURE 27 , 30A View FIGURE 30 ). Maxilliped 3 with well-developed flagellum on exopod ( Fig. 29B View FIGURE 29 ). Chelipeds relatively stouter in adult males ( Figs. 27A, E View FIGURE 27 , 30A View FIGURE 30 ). Ambulatory legs relatively stout, shorter, glabrous ( Fig. 27A, E View FIGURE 27 ). Male s2/s3 visible as groove; male s3/s4 only visible as 2 short lateral depressions ( Fig. 27D, H View FIGURE 27 ). Male sternopleonal cavity relatively short, reaching to imaginary line joining anterior part of cheliped coxae ( Fig. 27D, H View FIGURE 27 ). Male pleon relatively narrow, with concave lateral margins; pleonal somite 6 trapezoidal, relatively broad, proximal width ca. 1.3–1.9 times medial length ( Figs. 27D, H View FIGURE 27 , 29D View FIGURE 29 ). G1 relatively slender; ultimate article subconical, inverted funnel-shaped, relatively slender, relatively short, ca. 0.3 times length of penultimate article; penultimate article slender ( Figs. 28A, B, D, E View FIGURE 28 , 29E, G View FIGURE 29 ). G2 longer than G1, ca. 1.2–1.4 times G1 length; ultimate article long, ca. 0.4–0.5 times length of penultimate article ( Figs. 28C, F View FIGURE 28 , 29F, H View FIGURE 29 ). Vulvae relatively widely located from each other (VD/SW = ca. 0.2) ( Fig. 29J View FIGURE 29 ).

Etymology. The genus name is derived from the Nilgiri Hills of the central Western Ghats of India, which is the type locality of the type species. The gender of this genus is feminine.

Remarks. Nilgiriana gen. nov. currently includes two species, Ni. nilgiriensis ( Roux, 1931) comb. nov., and a new species, Ni. paloti sp. nov., described in the present study.

Nilgiriana gen. nov. can be separated from other freshwater crab genera of southern India by the relatively low carapace ( CH /CW = ca. 0.4) ( Figs. 27C, G View FIGURE 27 , 30A View FIGURE 30 ); the posterolaterally weakly developed postorbital cristae ( Fig. 27A, B, E, F View FIGURE 27 ); the broadly triangular external orbital angle, with the long outer margin, ca. 4–5 times the inner margin length ( Fig. 27A, B, E, F View FIGURE 27 ); the low epibranchial tooth ( Fig. 27A, B, E, F View FIGURE 27 ); the well-developed flagellum on the exopod of maxilliped 3 ( Fig. 29B View FIGURE 29 ); the relatively stouter pereiopods, with the ambulatory legs being shorter and glabrous ( Figs. 27A, E View FIGURE 27 , 30A View FIGURE 30 ); the male s2/s3 discernible as groove ( Fig. 27D, H View FIGURE 27 ); the relatively slender G1, with the subconical, inverted funnel-shaped and relatively short ultimate article (ca. 0.3 times the length of the penultimate article), and the relatively slenderer penultimate article ( Figs. 28A, B, D, E View FIGURE 28 , 29E, G View FIGURE 29 ); the distinctly longer G2, ca. 1.2–1.4 times the G1 length, with the long ultimate article, ca. 0.4–0.5 times length of penultimate article ( Figs. 28 View FIGURE 28 , 29E–H View FIGURE 29 ); the relatively widely located vulvae (VD/SW = ca. 0.2) ( Fig. 29J View FIGURE 29 ).

Nilgiriana gen. nov. is differentiated from Vanni View in CoL s. str. by the morphological features in postorbital cristae, external orbital angle, ambulatory legs, male pleonal somite 6, and G1 ultimate article (see Remarks for Vanni View in CoL ). This new genus should not be confused with Santanusus gen. nov. and Pusillosa gen. nov. due to the relatively stouter adult male chelipeds ( Figs. 27A, E View FIGURE 27 , 30A View FIGURE 30 ) (versus adult male chelipeds relatively slenderer; Figs. 22A, E View FIGURE 22 , 23A View FIGURE 23 , 25A, G View FIGURE 25 ; see Roux 1931: fig. 16); the glabrous ambulatory legs ( Fig. 27A, E View FIGURE 27 ) (versus ambulatory legs setose; Figs. 22A, E View FIGURE 22 , 23A View FIGURE 23 , 25A, H View FIGURE 25 ; see Roux 1931: fig. 16); and the subconical, inverted funnel-shaped G1 ultimate article, with the distal portion abruptly narrow ( Figs. 28A, B, D, E View FIGURE 28 , 29E, G View FIGURE 29 ) (versus G1 ultimate article conical, with the distal portion gradually narrow; Figs. 24A, B View FIGURE 24 , 26A, B View FIGURE 26 ; see Bahir & Yeo 2007: fig. 37D, E).

The general appearance of the carapace, especially the broadly triangular external orbital angle with the long outer margin, and the stouter, shorter and glabrous ambulatory legs, in Nilgiriana gen. nov., resembles those of Travancoriana View in CoL s. lat. (now Travancoriana View in CoL s. str., Ponmudiana gen. nov., Palaniana gen. nov., Anamudiana gen. nov., and Naduganiana gen. nov.). Nilgiriana gen. nov. can be identified as distinct from these genera mainly by the weakly developed postorbital cristae, which do not reach the lateral margins of the carapace ( Fig. 27A, B, E, F View FIGURE 27 ) (versus postorbital cristae well-developed, reaching the lateral margins of the carapace; Figs. 2A View FIGURE 2 , 4A, B, E, F View FIGURE 4 , 6A View FIGURE 6 , 7A View FIGURE 7 , 9A View FIGURE 9 , 10A View FIGURE 10 , 12A, B, E View FIGURE 12 ), and the subconical, distally abruptly narrow G1 ultimate article ( Figs. 28A, B, D, E View FIGURE 28 , 29E, G View FIGURE 29 ) (versus G1 ultimate article conical or subcylindrical, with the gradually narrow distal portion; Figs. 3A, B View FIGURE 3 , 5A, B, D, E View FIGURE 5 , 6F, G View FIGURE 6 , 8A, B View FIGURE 8 , 9F, G View FIGURE 9 , 11A, B View FIGURE 11 , 12H, I View FIGURE 12 , 13A, B View FIGURE 13 ).

Geographical distribution. Nilgiriana gen. nov. is distributed only in the central Western Ghats of Karnataka (Kodagu district), Kerala ( Kannur and Wayanad districts), and Tamil Nadu (Nilgiris district) in southern India ( Roux 1931; Bott 1970a, 1970b; Bahir & Yeo 2007; Pati et al. 2019c; present study) ( Fig. 1B View FIGURE 1 ).