Idukkiana giri ( Bahir & Yeo, 2007 ) Z, 2025

Z, Sameer Kumar Pati, 2025, Taxonomic revision of the freshwater crab genera Travancoriana Bott, 1969, and Vanni Bahir & Yeo, 2007 (Crustacea: Decapoda: Gecarcinucidae), with descriptions of eight new genera and two new species from the Western Ghats, southern India, Zootaxa 5634 (1), pp. 1-77 : 66-70

Idukkiana giri ( Bahir & Yeo, 2007) comb. nov.

[Idukki mountain crab]

( Figs. 31 , 32 )

Vanni giri Bahir & Yeo, 2007: 346 , figs. 43, 44.

Vanni giri – Rajesh et al. 2017: 146.—Pati 2020: 162 (list).— Pati & Pradhan 2020: 555836 (list).

Type material. Holotype: male ( CW 18.8 mm, CL 14.2 mm) ( ZRC 2003.0271 ), India, Kerala State, Idukki District , “between Munnar-Maraiyoor on Munnar-Pollachchi” [between Munnar-Marayoor on Munnar-Pollachi road], 10.13172° N, 77.05578° E, elev. 1570 m a.s.l., collector and collection date unknown.

Diagnosis. As for new genus.

Remarks. According to Bahir & Yeo (2007), the G2 ultimate article of Idukkiana giri comb. nov. is ca. 0.25 times the length of the penultimate article, which is certainly a typographical error. The G2 ultimate article of the holotype is conspicuously long, ca. 0.5 times the length of the penultimate article ( Fig. 32C ; see Bahir & Yeo 2007: fig. 43E).

The report of the species as Vanni giri by Pati et al. (2014) from the Chikkamagaluru and Kodagu districts of Karnataka is an error, which is evident from their figures (Pati et al. 2014: pl. 2 figs. 10–12, pl. 4 figs. 6–8). Their specimens actually belong to an undescribed species of Vanni (work in progress).

The entire Idukki district of Kerala lies in the southern Western Ghats, which is currently known for 15 species in 12 genera (cf. Bahir & Yeo 2007; Pati & Sharma 2013; Pati et al. 2014, 2017; Rajesh et al. 2017; Raj et al. 2021, 2022; present study). Idukkiana giri comb. nov. can be easily separated from the species of those genera mainly by its distinctive characteristics, including its relatively small size (maximum CW 18.8 mm), a low carapace ( CH /CW = ca. 0.4), a broadly triangular external orbital angle with a long outer margin (ca. 3.5 times the inner margin length), a low epibranchial tooth, a well-developed flagellum on the maxilliped 3 exopod, a relatively narrow male pleonal somite 6 (the proximal width ca. 1.1 times the medial length), a relatively shorter G1 ultimate article (ca. 0.3 times the length of the penultimate article), and a distinctly longer G2 with a length of ca. 1.2 times that of the G1 ( Figs. 31 , 32 ).

Ecological notes. Idukkiana giri comb. nov. was reported to inhabit moist soil and areas under stones, immediately adjacent to a streamlet, at an elevation of 1570 m a.s.l. ( Bahir & Yeo 2007).

Geographical distribution. As for new genus.

Key to the freshwater crab genera of southern India and/or the Western Ghats

1. Frontal medial triangle complete, with distinct upper margin and lateral margins (see Bahir & Yeo 2005: fig. 3B)......... 2

– Frontal medial triangle incomplete, with distinct upper margin only, lateral margins indiscernible ( Fig. 2B )............. 3

2. G1 ultimate article and distal portion of penultimate article not longitudinally twisted (see Bahir & Yeo 2005: fig. 3 E) ..................................................................................... Oziotelphusa Müller, 1887 [southern India, including central and southern Western Ghats ; Maharashtra and Odisha]

– G1 ultimate article and distal portion of penultimate article longitudinally twisted (see Pati et al. 2022a: fig. 7 A – C) ..................................................................................... Spiralothelphusa Bott, 1968 [southern India; Maharashtra, Odisha, and West Bengal]

3. Orbit with lower outer corner channelled (see Pati & Sharma 2014: fig. 1B).......................................

..................................................................... Gecarcinucus H. Milne Edwards, 1844

[Maharashtra; including northern Western Ghats] – Orbit with lower outer corner normal, not channelled ( Fig. 2B )................................................. 4

4. G2 distinctly shorter than G1, ca. ≤ 0.7 × G1 length (see Bahir & Yeo 2007: fig. 4A, D; Pati & Thackeray 2018: figs. 4D, F, 11I,

L, 17I, L, 24I, L; Pati et al. 2019a: fig. 3O, P; 2023b: fig. 6B, F; Pati & Yeo 2022: fig. 1H, I, Q, R).................... 5 – G2 equal to or longer than G1, ca. ≥ 1.0 × G1 length ( Figs. 3A, C , 28A, C )...................................... 13

5. Male s2/s3 indiscernible (see Pati & Thackeray 2018: figs. 4C, 11C, 17C, 24C); male sternopleonal cavity relatively long, reaching to or beyond imaginary line joining bases of maxilliped 3 (see Pati & Thackeray 2018: figs. 4C, 11C, 17C, 24C); G2 ultimate article usually conspicuously short, ca. 0.1 × length of penultimate article (see Pati & Thackeray 2018: figs. 4F, 11L, 17L, 24L)........................................................................................... 6

– Male s2/s3 distinct (see Bahir & Yeo 2007: fig. 5C; Pati et al. 2019a: fig. 2F; 2023b: fig. 2C; Pati & Yeo 2022: fig. 1F, O); male sternopleonal cavity relatively short, reaching to imaginary line joining anterior part of cheliped coxae (see Bahir & Yeo 2007: fig. 5C; Pati et al. 2019a: fig. 2F; 2023b: fig. 2C; Pati & Yeo 2022: fig. 1F, O); G2 ultimate article usually relatively long, ca. 0.2–0.3 × length of penultimate article (see Bahir & Yeo 2007: fig. 4D; Pati et al. 2019a: fig. 3P; 2023b: fig. 6F; Pati & Yeo 2022: fig. 1I)........................................................................................ 9

6. Male telson elongated (see Pati & Thackeray 2018: figs. 4C, 17C, G)............................................ 7 – Male telson relatively short (see Pati & Thackeray 2018: figs. 11C, G, 24C, G).................................... 8

7. Front with relatively narrow anterior margin (FW/CW = ca. 0.4) (see Pati & Thackeray 2018: fig. 4B); maxilliped 3 exopod relatively long, reaching beyond anterolateral corner of ischium (see Pati & Thackeray 2018: fig. 6H); G1 relatively stouter (see Pati & Thackeray 2018: fig. 4D)................................................. Ghatiana Pati & Sharma, 2014 [Goa, Karnataka, and Maharashtra; northern and central Western Ghats only]

– Front with relatively broad anterior margin (FW/CW = ca. 0.5) (see Pati & Thackeray 2018: fig. 17B); maxilliped 3 exopod relatively short, not reaching anterolateral corner of ischium (see Pati & Thackeray 2018: fig. 17H); G1 conspicuously slender (see Pati & Thackeray 2018: fig. 17I)................................................. Inglethelphusa Bott, 1970 [Maharashtra (Satara district); northern Western Ghats only]

8. Branchial regions relatively low (see Pati & Thackeray 2018: fig. 11A); ambulatory legs with sparsely setose dactylus and propodus (see Pati & Thackeray 2018: fig. 11A, E); male sternopleonal cavity relatively short, not reaching beyond imaginary line joining bases of maxilliped 3 (see Pati & Thackeray 2018: fig. 11C)..................... Gubernatoriana Bott, 1970 [Maharashtra; northern Western Ghats only]

– Branchial regions relatively inflated (see Pati & Thackeray 2018: fig. 24A); ambulatory legs with abundantly setose dactylus and/or propodus (see Pati & Thackeray 2018: fig. 24A, E); male sternopleonal cavity relatively long, reaching beyond imaginary line joining bases of maxilliped 3 (see Pati & Thackeray 2018: fig. 24C)............. Sahyadriana Pati & Thackeray, 2018 [Maharashtra; northern Western Ghats only]

9. Carapace ovate, relatively narrow (CW/CL = ca. 1.2–1.4), relatively deep ( CH /CW = ca. 0.5–0.7) (see Bahir & Yeo 2007: fig. 5A, B; Pati et al. 2019a: fig. 2D, E; 2023b: fig. 2A, B); epistome posterior margin with strongly sinuous lateral lobes (see Bahir & Yeo 2007: fig. 5B; Pati et al. 2019a: fig. 2E; 2023b: fig. 2B); male sternopleonal cavity relatively short, reaching to imaginary line joining medial part of cheliped coxae (see Bahir & Yeo 2007: fig. 5C; Pati et al. 2019a: fig. 2F; 2023b: fig. 2C)..... 10

– Carapace subovate, relatively broad (CW/CL = ca. 1.4–1.5), relatively low ( CH /CW = ca. 0.4–0.5) (see Pati & Yeo 2022: fig. 1A, B, J, K); epistome posterior margin with concave lateral lobes (see Pati & Yeo 2022: fig. 1B, K); male sternopleonal cavity relatively long, reaching to imaginary line joining anterior part of cheliped coxae (see Pati & Yeo 2022: fig. 1F, O)...... 12

10. Male telson narrow, elongated, medial length ca. 1.3–1.4 × proximal width (see Pati et al. 2023b: fig. 6A); G1 ultimate article relatively stouter (see Pati et al. 2023b: fig. 6B); G1 penultimate article with characteristically convex distal inner margin (see Pati et al. 2023b: fig. 6B)................................................ Aradhya Pati, Bajantri & Hegde, 2023 [Karnataka (Uttara Kannada district); central Western Ghats only]

– Male telson relatively broader, shorter, medial length ca. 0.9–1.1 × proximal width (see Bahir & Yeo 2007: fig. 5C; Pati et al. 2019a: fig. 2F); G1 ultimate article relatively slender (see Bahir & Yeo 2007: fig. 4A; Pati et al. 2019a: fig. 3O); G1 penultimate article with almost straight distal inner margin (see Bahir & Yeo 2007: fig. 4A; Pati et al. 2019a: fig. 3O).............. 11

11. Carapace dorsal surface generally smooth, lacking distinct serrations on anterolateral margins (see Pati et al. 2019a: fig. 2A, D); cervical grooves relatively shallow (see Pati et al. 2019a: fig. 2A, D); maxilliped 3 lacking flagellum or with relatively short flagellum, reaching about half width of merus (see Pati et al. 2019a: fig. 3B, N); male pleonal somite 6 relatively broad, proximal width ca. 1.7–1.8 × medial length (see Pati et al. 2019a: fig. 2C, F); G1 relatively stout, with large flexible zone (see Pati et al. 2019a: fig. 3E, O).............................................. Arcithelphusa Pati & Sudha Devi, 2015 [Kerala (Wayanad district); central Western Ghats only]

– Carapace dorsal surface relatively rugose, with distinct serrations on anterolateral margins (see Bahir & Yeo 2007: fig. 5A; Pati et al. 2017: fig. 11a); cervical grooves relatively deep (see Bahir & Yeo 2007: fig. 5A; Pati et al. 2017: fig. 11a); maxilliped 3 with relatively long flagellum, reaching beyond half width of merus ( Pati et al. 2017: fig. 11i); male pleonal somite 6 relatively narrow, proximal width ca. 1.3–1.6 × medial length (see Bahir & Yeo 2007: fig. 5C; Pati et al. 2017: fig. 11h); G1 relatively slender, with small flexible zone (see Bahir & Yeo 2007: fig. 4A; Pati et al. 2017: fig. 12a)....................................................................................................... Cylindrotelphusa Alcock, 1909 [Kerala and Tamil Nadu (Nilgiris district); including central and southern Western Ghats]

12. Epibranchial tooth low, weakly developed, located anterior to level of postorbital cristae (see Pati & Yeo 2022: fig. 1J); cervical grooves relatively short, not reaching to level of postorbital cristae (see Pati & Yeo 2022: fig. 1J); subhepatic region smooth (see Pati & Yeo 2022: fig. 1K); major cheliped with relatively stout palm (see Pati & Yeo 2022: fig. 1N); male pleon relatively broad, with trapezoidal and relatively broader pleonal somite 6, proximal width ca. 1.3–1.7 × medial length (see Pati & Yeo 2022: fig. 1P); G1 relatively long, tip reaching beyond s5/s6, ultimate article relatively long, ca. 0.7–0.8 × length of penultimate article (see Pati & Yeo 2022: fig. 1O, Q)................................................ Barusa Pati & Yeo, 2022 [peninsular India, including southern India ( Andhra Pradesh , Karnataka, and Telangana), and northern and central Western Ghats]

– Epibranchial tooth distinct, relatively strongly developed, located at same level of postorbital cristae (see Pati & Yeo 2022: fig. 1A); cervical grooves relatively long, reaching to level of postorbital cristae (see Pati & Yeo 2022: fig. 1A); subhepatic region relatively rugose (see Pati & Yeo 2022: fig. 1B); major cheliped with relatively slender palm (see Pati & Yeo 2022: fig. 1E); male pleon relatively narrow, with subquadrate and relatively narrower pleonal somite 6, proximal width ca. 1.2 × medial length (see Pati & Yeo 2022: fig. 1G); G1 relatively short, tip reaching to proximal half of s6, ultimate article relatively short, ca. 0.6 × length of penultimate article (see Pati & Yeo 2022: fig. 1F, H)........................... Barytelphusa Alcock, 1909 [peninsular India, including southern India and Western Ghats]

13. Maxilliped 3 completely lacking flagellum on exopod (see Bahir & Yeo 2007: figs. 25B, 27A)...................... 14 – Maxilliped 3 with distinct flagellum on exopod ( Figs. 16E , 29B ).............................................. 16

14. Postorbital cristae strongly developed (see Pati et al. 2017: fig. 2a); external orbital angle acutely triangular, with short outer margin, ca. 2 × length of inner margin (see Pati et al. 2017: fig. 2a); G2 slightly longer than G1, with relatively short ultimate article, ca. 0.3 × length of penultimate article (see Pati et al. 2017: fig. 3a, d).......................................................................................... Karkata Pati, Rajesh, Raj, Sheeja, Kumar & Sureshan, 2017 [Kerala (Ernakulam and Idukki districts); southern Western Ghats only]

– Postorbital cristae indiscernible or weakly developed (see Bahir & Yeo 2007: figs. 25A, 26A, 28A); external orbital angle broadly triangular, with long outer margin, ca. 3–4 × length of inner margin (see Bahir & Yeo 2007: figs. 25A, 26A, 28A); G2 distinctly longer than G1, with relatively long ultimate article, ca. 0.4.–0.5 × length of penultimate article (see Bahir & Yeo 2007: figs. 25F, H, 27C, G)............................................................................ 15

15. Ambulatory legs with densely setose carpus, propodus, and dactylus (see Bahir & Yeo 2007: fig. 25E); male s2/s3 and s3/s4 indiscernible (see Bahir & Yeo 2007: fig. 25C)......................................... Pilarta Bahir & Yeo, 2007 [Kerala (Ernakulam and Thiruvananthapuram districts); southern Western Ghats only]

– Ambulatory legs with sparsely setose carpus, propodus, and dactylus (see Bahir & Yeo 2007: fig. 28A); male s2/s3 and s3/s4 distinct, deep (see Bahir & Yeo 2007: figs. 28C, 29A).................................... Snaha Bahir & Yeo, 2007 [Kerala (Idukki district) and Tamil Nadu (Dindigul district); southern Western Ghats only]

16. Postorbital cristae indiscernible (see Raj et al. 2022: fig. 3B)....................... Pavizham Raj, Kumar & Ng, 2022 [Kerala (Pathanamthitta district); southern Western Ghats only]

– Postorbital cristae discernible, weakly to strongly developed ( Figs. 2A , 22B , 25B , 27B )............................ 17

17. Epibranchial tooth prominent, located posterior to level of postorbital cristae (see Bahir & Yeo 2007: fig. 23A)...........

............................................................................. Lamella Bahir & Yeo, 2007

[Kerala; including southern Western Ghats] – Epibranchial tooth relatively low, located at same level of postorbital cristae ( Figs. 2A , 12B , 14A , 25B , 27F )........... 18

18. Carapace with strongly convex lateral margins (see Kumar et al. 2017: fig. 5B); ambulatory legs exceptionally long, longest merus ca. 6–7 × longer than broad (see Kumar et al. 2017: figs. 5A, 7H)................... Kani Kumar, Raj & Ng, 2017 [Kerala (Thiruvananthapuram district); southern Western Ghats only]

– Carapace with gently to moderately convex lateral margins ( Figs. 2A , 12B , 14A , 25B , 27F ); ambulatory legs relatively short, longest merus ca. ≤ 4 × longer than broad ( Figs. 2A , 12A , 14A , 25A, H , 27E ).................................... 19

19. Carapace deep ( CH /CW = ca. 0.6) (see Raj et al. 2021: fig. 3B); female vulvae closely located to each other (VD/SW = ca. 0.1) (see Raj et al. 2021: fig. 5C).............................................. Rajathelphusa Raj, Kumar & Ng, 2021 [Kerala (Idukki district); southern Western Ghats only]

– Carapace usually low ( CH /CW = ca. 0.3–0.5) ( Figs. 10B , 16B ); female vulvae located some distance from each other (VD/SW = ca. ≥ 0.2) ( Figs. 10F , 16J )............................................................................ 20

20. External orbital angle acutely triangular to triangular, with short outer margin, ca. 2–2.5 × length of inner margin ( Figs. 14A , 16A , 18A , 20A , 22A ; see Bahir & Yeo 2007: figs. 19A, 46A)................................................. 21

– External orbital angle broadly triangular, with long outer margin, ca. 3–5 × length of inner margin ( Figs. 2A , 4A, E , 7A , 10A , 12A , 25A , 27A, E , 31A ).............................................................................. 24

21. Male s3/s4 distinct, deep (see Bahir & Yeo 2007: figs. 18A, 45A).............................................. 22 – Male s3/s4 indiscernible ( Figs. 14C , 16C , 18D , 20D , 22D )................................................... 23

22. Male pleonal somite 6 relatively broad, proximal width ca. 1.2–1.6 × medial length (see Bahir & Yeo 2007: fig. 18B); G1 ultimate article relatively stouter, broadly conical (see Bahir & Yeo 2007: fig. 18C); G2 ultimate article relatively short, ca. 0.3 × length of penultimate article (see Bahir & Yeo 2007: fig. 18G).......................... Baratha Bahir & Yeo, 2007 [Kerala (Idukki district); southern Western Ghats only]

– Male pleonal somite 6 relatively narrow, proximal width ca. 0.8–0.9 × medial length (see Bahir & Yeo 2007: fig. 45B); G1 ultimate article relatively slenderer, narrowly conical/subconical (see Bahir & Yeo 2007: fig. 45C); G2 ultimate article relatively long, ca. 0.4–0.5 × length of penultimate article (see Bahir & Yeo 2007: fig. 45F)................ Vela Bahir & Yeo, 2007 [Karnataka (Kodagu and Uttara Kannada districts), Kerala (Idukki, Kozhikode, Palakkad, and Wayanad districts), and Tamil Nadu (Nilgiris district); central and southern Western Ghats only]

23. Postorbital cristae well-developed, reaching lateral margins of carapace ( Figs. 14A , 16A , 18A, B , 20A, B ); epistome posterior margin with well-developed, triangular medial tooth ( Figs. 14B , 16B , 18C , 20C ); male s2/s3 discernible ( Figs. 14C , 16C , 18D , 20D ); male sternopleonal cavity relatively short, reaching to imaginary line joining anterior part of cheliped coxae ( Figs. 14C , 16C , 18D , 20D ); G2 ultimate article relatively long, ca. 0.4 × length of penultimate article ( Figs. 15C , 17C , 19C , 21C ).................................................................................... Vanni Bahir & Yeo, 2007 [Karnataka (as north as Uttara Kannada district), Kerala, and Tamil Nadu (as south as Kanyakumari district); central and southern Western Ghats only]

– Postorbital cristae weakly developed posterolaterally, not reaching lateral margins of carapace ( Fig. 22A, B ); epistome posterior margin with low, broadly triangular medial tooth ( Fig. 22C ); male s2/s3 indiscernible ( Fig. 22D ); male sternopleonal cavity relatively long, reaching to imaginary line joining bases of maxilliped 3 ( Fig. 22D ); G2 ultimate article relatively short, ca. 0.3 × length of penultimate article ( Fig. 24C ).................................................. Santanusus gen. nov. [Kerala ( Kozhikode, Palakkad , and Thrissur districts) and Tamil Nadu (Coimbatore district); central and southern Western Ghats only]

24. Postorbital cristae weakly developed posterolaterally, not reaching lateral margins of carapace ( Figs. 25A, B , 27A, B, E, F ; see

Bahir & Yeo 2007: figs. 37A, 38A)...................................................................... 25 – Postorbital cristae well-developed, reaching lateral margins of carapace ( Figs. 2A , 4A, E , 7A , 10A , 12A , 31A )......... 26

25. Chelipeds relatively slender in adult males ( Fig. 25G ; see Roux 1931: fig. 16); ambulatory legs relatively slender, longer, setose ( Fig. 25A, H ; see Roux 1931: fig. 16); male s2/s3 indiscernible ( Fig. 25D ; see Bahir & Yeo 2007: figs. 37B, 38C); male pleon with strongly concave, rather angular lateral margins ( Fig. 25D, I ; see Bahir & Yeo 2007: figs. 37C, 38C); G1 relatively stout, with conical ultimate article and relatively stouter penultimate article ( Fig. 26A, B ; see Bahir & Yeo 2007: fig. 37D, E)......................................................................................... Pusillosa gen. nov. Tamil Nadu (Nilgiris district); central Western Ghats only]

– Chelipeds relatively stout in adult males ( Fig. 27A, E ); ambulatory legs relatively stout, shorter, glabrous ( Fig. 27A, E ); male s2/s3 discernible ( Fig. 27D, H ); male pleon with relatively less strongly concave lateral margins ( Figs. 27D, H , 29D ); G1 relatively slender, with subconical, inverted funnel-shaped ultimate article and relatively slenderer penultimate article ( Figs. 28A, B, D, E , 29E ).................................................................... Nilgiriana gen. nov. [Karnataka ( Kodagu district ), Kerala ( Kannur and Wayanad districts), and Tamil Nadu (Nilgiris district); central Western Ghats only]

26. Male s3/s4 only visible as 2 short lateral depressions ( Fig. 4D, H ); G1 penultimate article slender ( Fig. 5A, B, D, E )......................................................................................... Ponmudiana gen. nov. [Kerala (Kollam and Thiruvananthapuram districts) and Tamil Nadu (Kanyakumari and Tirunelveli districts); southern Western Ghats only]

– Male s3/s4 visible as complete groove, reaching edge of sternum ( Figs. 2C , 7C , 10D , 12D , 31C ); G1 penultimate article relatively stouter ( Figs. 3A, B , 8A, B , 11A, B , 13A, B , 32A, B )............................................... 27

27. Male pleon relatively broad, with almost straight lateral margins, pleonal somite 6 trapezoidal ( Fig. 7C ); G1 ultimate article relatively stout, long, ca. 0.5–0.6 × length of penultimate article ( Fig. 8A, B )....................... Palaniana gen. nov. [Kerala (Idukki, Palakkad, Pathanamthitta, and Thrissur districts) and Tamil Nadu (Coimbatore, Dindigul, and Theni districts); southern Western Ghats only]

– Male pleon relatively narrow, with concave to strongly concave lateral margins, pleonal somite 6 subquadrate ( Figs. 2C , 10D , 12D , 31C ); G1 ultimate article relatively slender, short, ca. 0.25–0.4 × length of penultimate article ( Figs. 3A, B , 11A, B , 13A, B , 32A, B ).......................................................................................... 28

28. Male sternopleonal cavity relatively shorter, reaching to imaginary line joining medial part of cheliped coxae ( Fig. 10D ); male pleonal somite 6 relatively broad, proximal width ca. 1.5 × medial length ( Fig. 10D, E )............ Anamudiana gen. nov. [Kerala (Idukki district); southern Western Ghats only]

– Male sternopleonal cavity relatively longer, reaching to imaginary line joining anterior part of cheliped coxae ( Figs. 2C , 12D , 31C ); male pleonal somite 6 relatively narrow, proximal width ca. 1.1–1.2 × medial length ( Figs. 2C , 12D , 31C )........ 29

29. Large sized crabs (maximum CW 55.3 mm); male telson relatively narrower, medial length ca. 1.2 × proximal width ( Fig. 2C ); G1 ultimate article distally gently curved inwards ( Fig. 3A, B ); G2 as long as G1, ca. 1.0 × G1 length ( Fig. 3 )........................................................................................... Travancoriana Bott, 1969 [Tamil Nadu state (Nilgiris district); central Western Ghats only]

– Medium sized crabs (maximum CW 28.0 mm); male telson relatively broader, medial length ca. 1.0 × proximal width ( Figs. 12D , 31C ); G1 ultimate article distally gently to distinctly curved outwards ( Figs. 13A, B , 32A, B ); G2 longer than G1, ca. 1.2 × G1 length ( Figs. 13 , 32 )............................................................................. 30

30. Male s2/s3, s3/s4 relatively shallow ( Fig. 31C ); male pleonal somite 6 and telson with straight lateral margins ( Fig. 31C ); G1 ultimate article relatively stouter, with relatively acute and straight tip ( Fig. 32A, B ); G1 penultimate article relatively slenderer, with almost straight outer margin ( Fig. 32A, B ).............................................. Idukkiana gen. nov. [Kerala (Idukki district); southern Western Ghats only]

– Male s2/s3, s3/s4 relatively deep ( Fig. 12D ); male pleonal somite 6 and telson with gently concave lateral margins ( Fig. 12D ); G1 ultimate article relatively slenderer, with blunt and bent tip ( Fig. 13A, B ); G1 penultimate article relatively stouter, with sinuous outer margin ( Fig. 13A, B )..................................................... Naduganiana gen. nov. [Kerala (Malappuram district) and Tamil Nadu (Nilgiris district); central Western Ghats only]

General discussion

Southern India is now known to have 63 species of freshwater crabs, belonging to 27 genera of the family Gecarcinucidae ; whereas the Western Ghats is home to 81 species of gecarcinucid crabs, spanning 30 genera ( Alcock 1910; Roux 1931; Bott 1970b; Bahir & Yeo 2005, 2007; Pati et al. 2017, 2019a, 2019c, 2022a, 2022b, 2023a, 2023b, 2023c, 2024; Rajesh et al. 2017; Pati & Thackeray 2018, 2021; Pati & Vargila 2019; Pati & Pradhan 2020; Raj et al. 2021, 2022; Mandal et al. 2022a, 2022b; Pati & Yeo 2022; present study) ( Table 1). The southern Indian state of Kerala currently possesses 39 species of freshwater crabs in 22 genera, followed by Tamil Nadu with 20 species in 14 genera, Karnataka with 13 species in nine genera, Telangana with six species in four genera, and Andhra Pradesh with five species in four genera ( Table 1). Among three major regions of the Western Ghats, the southern Western Ghats is now known for 18 genera and 31 species of freshwater crabs, the central Western Ghats for 14 genera and 23 species, and the northern Western Ghats for seven genera and 35 species ( Table 1).

The present taxonomic revision of the gecarcinucid freshwater crab genera, Travancoriana and Vanni , recognizes eight new genera and two new species from the Western Ghats of southern India based on the morphological and molecular evidence. This fact highlights the presence of many undescribed taxa in the region, warranting further exploration ( Pati & Pradhan 2020). Freshwater crabs play important ecological roles in tropical ecosystems ( Yeo et al. 2008; Cumberlidge et al. 2009), and a better understanding of the diversity, distribution, and ecology of freshwater crabs is essential for conservation and management efforts. The identification keys furnished here for the freshwater crab genera or species is a crucial step, which will help carcinologists currently working in the region. These identification keys, however, need refining with the discoveries of additional taxa in future.

In conclusion, the taxonomy of freshwater crabs in southern India, especially in the Western Ghats, is still in a state of flux, and continued research is necessary to discover more taxa, resolve their phylogenetic relationships, and understand their diversity, distribution, and ecology.

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Figures

FIGURE 2. Travancoriana schirnerae Bott, 1969, holotype male (45.1 mm × 31.6 mm) (MHNG, uncatalogued). A, overall habitus; B, frontal view of cephalothorax; C, thoracic sternites, pleonal somites 4–6, and telson. Scale bar = 10 mm. (Figure reproduced from Bahir & Yeo (2007: fig. 8A–C)).

FIGURE 3. Travancoriana schirnerae Bott, 1969, holotype male (45.1 mm × 31.6 mm) (MHNG, uncatalogued). A, right G1 dorsal view; B, right G1 ventral view; C, right G2. Scale bar = 1 mm. (Figure redrawn from Bahir & Yeo (2007: fig. 6A, B, E)).

FIGURE 4. A–D, Ponmudiana charu (Bahir & Yeo, 2007) comb. nov., holotype male (40.4 × 30.7 mm) (ZRC 2003.0241); E–H, Ponmudiana pollicaris (Alcock, 1909) comb. nov., lectotype male (52.1 × 38.1 mm) (ZSIK 1779–87/10). A, E, overall habitus; B, F, dorsal view of cephalothorax; C, G, frontal view of cephalothorax; D, H, thoracic sternites, pleonal somites 4–6, and telson. Scale bar = 10 mm. (Figure 4E–H reproduced from Bahir & Yeo (2007: fig. 10A–C)).

FIGURE 5. A–C, Ponmudiana charu (Bahir & Yeo, 2007) comb. nov., holotype male (40.4 × 30.7 mm) (ZRC 2003.0241); D–F, Ponmudiana pollicaris (Alcock, 1909) comb. nov., lectotype male (52.1 × 38.1 mm) (ZSIK 1779–87/10). A, D, left G1 dorsal view; B, E, left G1 ventral view; C, F, left G2. Scale bar = 1 mm. (Figure 5D–F redrawn from Bahir & Yeo (2007: fig. 9A, B, E)).

FIGURE 7. Palaniana convexa (Roux, 1931) comb. nov., lectotype male (51.2 × 37.8 mm) (MHNG, uncatalogued). A, overall habitus; B, frontal view of cephalothorax; C, thoracic sternites, pleonal somites 4–6, and telson. Scale bars: A, B = 20 mm, C = 10 mm. (Figure reproduced from Bahir & Yeo (2007: fig. 13A–C)).

FIGURE 8. Palaniana convexa (Roux, 1931) comb. nov., lectotype male (51.2 × 37.8 mm) (MHNG, uncatalogued). A, right G1 dorsal view; B, right G1 ventral view; C, right G2. Scale bar = 2 mm. (Figure redrawn from Bahir & Yeo (2007: fig. 11A, B, E)).

FIGURE 10. Anamudiana granulata (Pati & Sharma, 2013) comb. nov. A, B, D, E, holotype male (33.7 × 26.1 mm) (ZSI- WRC C.1132); C, paratype male (35.4 mm × 26.9 mm) (ZSI-WRC C.579); F, paratype female (39.7 mm × 29.7 mm) (ZSI-WRC C.572). A, overall habitus; B, frontal view of cephalothorax; C, left maxilliped 3; D, thoracic sternites, pleonal somites 4–6, and telson; E, pleon and telson; F, thoracic sternites showing vulvae. Scale bars: A, B = 10 mm, C–F = 5 mm.

FIGURE 11. Anamudiana granulata (Pati & Sharma, 2013) comb. nov., holotype male (33.7 × 26.1 mm) (ZSI-WRC C.1132). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm.

FIGURE 12. Naduganiana kuleera (Bahir & Yeo, 2007) comb. nov. A–D, holotype male (28.0 mm × 19.7 mm) (ZRC 2003.0240); E–J, male (19.3 mm × 14.6 mm) (ZSI-WRC C.2470); K, female (19.3 mm × 14.5 mm) (ZSI-WRC C.2470). A, E, overall habitus; B, dorsal view of cephalothorax; C, frontal view of cephalothorax; D, thoracic sternites, pleonal somites 4–6, and telson; F, left maxilliped 3; G, pleon and telson; H, left G1 dorsal view; I, left G1 ventral view; J, left G2; K, thoracic sternites showing vulvae. Scale bars: A–C, E = 10 mm, D, K = 5 mm, F, G = 2 mm, H–J = 1 mm.

FIGURE 13. Naduganiana kuleera (Bahir & Yeo, 2007) comb. nov., holotype male (28.0 × 19.7 mm) (ZRC 2003.0240).A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm.

FIGURE 14. Vanni travancorica (Henderson, 1913). A–E, male (18.3 × 14.1 mm) (ZSI-WRC C.1874); F, female (21.7 × 16.7 mm) (ZSI-WRC C.1874). A, overall habitus; B, frontal view of cephalothorax; C, thoracic sternites, pleonal somites 4–6, and telson; D, left maxilliped 3; E, pleon and telson; F, thoracic sternites showing vulvae. Scale bars: A = 10 mm, B, C, E, F = 5 mm, D = 2 mm.

FIGURE 15. Vanni travancorica (Henderson, 1913), male (18.3 mm × 14.1 mm) (ZSI-WRC C.1874). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm.

FIGURE 16. Vanni gracilis sp. nov. A–H, holotype male (23.8 × 17.5 mm) (ZSI-WGRC IR/INV/9192A); I, J, paratype female (20.2 × 14.7 mm) (ZSI-WGRC IR/INV/9192B). A, overall habitus; B, frontal view of cephalothorax; C, overall ventral view; D, mouth parts exposed; E, left maxilliped 3; F, outer view of chelae; G, thoracic sternites showing right G1 and G2; H, pleon and telson; I, pleonal somites 4–6 and telson; J, thoracic sternites showing vulvae. Scale bars: A–C, F = 10 mm, D, E = 2 mm, G–J = 5 mm.

FIGURE 17. Vanni gracilis sp. nov., holotype male (23.8 × 17.5 mm) (ZSI-WGRC IR/INV/9192A). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm.

FIGURE 18. Vanni deepta Bahir & Yeo, 2007. A–D, holotype male (17.8 × 12.8 mm) (ZRC 2003.0233); E–J, male (21.5 × 15.8 mm) (ZSI-WRC C.2108); K, female (22.2 × 16.5 mm) (ZSI-WRC C.2168). A, E, overall habitus; B, dorsal view of cephalothorax; C, frontal view of cephalothorax; D, thoracic sternites, pleonal somites 4–6, and telson; F, left maxilliped 3; G, pleon and telson; H, left G1 dorsal view; I, left G1 ventral view; J, left G2; K, thoracic sternites showing vulvae. Scale bars: A–C, E = 10 mm, D, G, K = 5 mm, F = 2 mm, H–J = 1 mm.

FIGURE 19. Vanni deepta Bahir & Yeo, 2007, holotype male (17.8 × 12.8 mm) (ZRC 2003.0233). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm.

FIGURE 20. Vanni ashini Bahir & Yeo, 2007. A–D, holotype male (24.1 × 18.5 mm) (ZRC 2003.0232); E–J, male (16.5 × 12.9 mm) (ZSI-WRC C.2322); K, female (15.3 × 12.0 mm) (ZSI-WRC C.2322). A, E, overall habitus; B, dorsal view of cephalothorax; C, frontal view of cephalothorax; D, thoracic sternites, pleonal somites 4–6, and telson; F, left maxilliped 3; G, pleon and telson; H, left G1 dorsal view; I, left G1 ventral view; J, left G2; K, thoracic sternites showing vulvae. Scale bars: A–C, E = 10 mm, D, K = 5 mm, F, G = 2 mm, H–J = 1 mm.

FIGURE 21. Vanni ashini Bahir & Yeo, 2007, holotype male (24.1 × 18.5 mm) (ZRC 2003.0232). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm.

FIGURE 22. Santanusus malabaricus (Henderson,1912) comb.nov.A–D, lectotypemale (13.6× 10.1 mm) (NHM1913.2.11.1); E–H, paralectotype male (18.0 × 13.2 mm) (ZSIK 7936/10). A, E, overall habitus; B, F, dorsal view of cephalothorax; C, G, frontal view of cephalothorax; D, thoracic sternites and pleonal somites 4, 5; H, thoracic sternites, pleonal somites 4–6, and telson. Scale bars: A–D, F–H = 5 mm, E = 10 mm. (Figure 22A–D reproduced from Bahir & Yeo (2007: fig. 34A–C)).

FIGURE 24. Santanusus malabaricus (Henderson, 1912) comb. nov., lectotype male (13.6 × 10.1 mm) (NHM 1913.2.11.1). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm. (Figure redrawn from Bahir & Yeo (2007: fig. 33A–C)).

FIGURE 25. Pusillosa pusilla (Roux, 1931) comb. nov. A–I, male (9.9 × 7.3 mm) (ZSI-WRC C.2342); J, female (8.3 × 6.5 mm) (ZSI-WRC C.2343).A, overall habitus; B, dorsal view of cephalothorax; C, frontal view of cephalothorax; D, thoracic sternites, pleonal somites 4–6, and telson; E, mouth parts exposed; F, left maxilliped 3; G, outer view of chelae; H, right ambulatory leg (P3); I, pleon and telson; J, thoracic sternites showing vulvae. Scale bars: A = 5 mm, B–D, F, G–J = 2 mm, E = 1 mm.

FIGURE 26. Pusillosa pusilla (Roux, 1931) comb. nov., male (9.9 × 7.3 mm) (ZSI-WRC C.2342). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 0.5 mm.

FIGURE 27. A–D, Nilgiriana nilgiriensis (Roux, 1931) comb. nov., lectotype male (24.7 × 18.5 mm) (MHNG, uncatalogued); E–H, Nilgiriana paloti sp. nov., holotype male (20.8 × 15.4 mm) (ZSI-WRC C.2477).A, E, overall habitus; B, F, dorsal view of cephalothorax; C, G, frontal view of cephalothorax; D, H, thoracic sternites, pleonal somites 4–6, and telson. Scale bars: A–C, E–G = 10 mm, D, H = 5 mm. (Figure 27A–D reproduced from Bahir & Yeo (2007: fig. 36A–C)).

FIGURE 28. A–C, Nilgiriana nilgiriensis (Roux, 1931) comb. nov., lectotype male (24.7 × 18.5 mm) (MHNG, uncatalogued); D–F, Nilgiriana paloti sp. nov., holotype male (20.8 × 15.4 mm) (ZSI-WRC C.2477). A, right G1 dorsal view; B, right G1 ventral view; C, right G2; D, left G1 dorsal view; E, left G1 ventral view; F, left G2. Scale bar = 1 mm. (Figure 28A–C redrawn from Bahir & Yeo (2007: fig. 35C, D, G)).

FIGURE 29. Nilgiriana paloti sp. nov. A–F, holotype male (20.8 × 15.4 mm) (ZSI-WRC C.2477); G, H, paratype male (18.3 × 12.6 mm) (ZSI-WRC C.1826); I, J, paratype female (19.1 × 13.3 mm) (ZSI-WRC C.1826). A, mouth parts exposed; B, left maxilliped 3; C, posterior thoracic sternites (s5–s8) showing right G1 and G2; D, pleon and telson; E, G, left G1 dorsal view; F, H, left G2; I, pleonal somites 4–6 and telson; J, thoracic sternites showing vulvae. Scale bars: A–C = 2 mm, D, I, J = 5 mm, E–H = 1 mm.

FIGURE 31. Idukkiana giri (Bahir & Yeo, 2007) comb. nov., holotype male (18.8 × 14.2 mm) (ZRC 2003.0271). A, overall habitus; B, frontal view of cephalothorax; C, thoracic sternites, pleonal somites 4–6, and telson. Scale bar = 5 mm. (Figure reproduced from Bahir & Yeo (2007: fig. 44A–C)).

FIGURE 32. Idukkiana giri (Bahir & Yeo, 2007) comb. nov., holotype male (18.8 × 14.2 mm) (ZRC 2003.0271). A, left G1 dorsal view; B, left G1 ventral view; C, left G2. Scale bar = 1 mm. (Figure redrawn from Bahir & Yeo (2007: fig. 43A, B, E)).