Walkerana muduga, Dinesh & Vijayakumar & Ramesh & Jayarajan & Chandramouli & Shanker, 2020

Dinesh, K. P., Vijayakumar, S. P., Ramesh, Vijay, Jayarajan, Aditi, Chandramouli, S. R. & Shanker, Kartik, 2020, A deeply divergent lineage of Walkerana (Anura: Ranixalidae) from the Western Ghats of Peninsular India, Zootaxa 4729 (2), pp. 266-276 : 269-271

Walkerana muduga sp. nov.

( Table 1 , 2 ; Fig. 1,2,3,4,5)

Holotype: ZSI / WRC /A/2211 ( CESF 1607 ), an adult male ( SVL 27.9 mm) collected by S.P. Vijayakumar and team in October 2010 from Muthikulam, (N 10.945; E 76.644) a high elevation site (1544 amsl) in the hill range Elivalmala / Elivalmalai located north of Palghat Gap.

Paratype: ZSI / WRC /A/2212 ( CESF 1606 ), an adult female ( SVL 44.9 mm) , collection data same as the holotype .

Etymology: The new species is named after the “Mudugar” indigenous community of Palghat district, Kerala who speak ‘Muduga’ language ( Menon, 1996). The species epithet is used as an invariable noun in apposition to the generic name. The suggested common name is ‘Muduga mountain leaping frog’.

Lineage diagnosis: Walkerana muduga sp. nov. can be diagnosed phylogenetically as a member of the ‘ Walkerana clade’ ( Fig. 2 ), and exhibits 5.7% genetic divergence from W. leptodactyla , 7.5% divergence from W. phrynoderma and 11.7% divergence from W. diplosticta at the 16S rRNA fragment. The species is highly divergent in morphology from all known species (see comparison section). Phylogenetic analysis also shows another undescribed lineage from the adjacent massif (north of Elival Mala), exhibiting high genetic divergence of 3.8 % for 16S rRNA (CESF 1554). However, due to the availability of only a single poorly preserved specimen (CESF 1554), we defer the description of this lineage.

Description of Holotype ZSI/WRC/A/2211 (CESF 1607) ( Fig. 2 , 3 ). A medium sized species of Walkerana (SVL = 27.9 mm) with squat, raised body; head width (HW = 11.3 mm) sub equal to head length (HL = 10.3 mm); snout bluntly pointed (ES = 4.7 mm) in both dorsal and ventral view and more than 1.2 times of eye diameter (ED = 3.9 mm); canthus rostralis angular, loreal region concave, inter orbital space flat (IO = 3.0 mm) and sub equal to upper eye lid (UEW = 2.4 mm); nostrils oval, nearer to tip of snout than to eye; eyes relatively smaller (EL/HL = 0.37), protruding out of the head; tympanum (TYH = 2.2 mm) distinct below the supratympanic fold and 1.7 times of eye diameter; minute vomerine ridges present with 2 to 3 spinular teeth; tongue bifid with a raised papilla; symphysial knob weak.

Fore arm slender (UAL = 4.7 mm) and sub equal to hand (PAL = 7.6 mm); fingers short and thin (dermal fringes distinct in the ventral view on the finger 2, 3 and 4); first finger shorter than second (f1 = 3.7 mm and f2 = 4.2 mm); finger tips with truncated enlarged discs with minute dorsoterminal grooves; fingers free without webbing between fingers; rounded subarticular tubercles moderate (one each on finger 1 and 2, and two each on finger 3 and 4); prepollex indistinct and palmar tubercle distinct, supernumerary tubercles absent.

Hind limbs moderately long, strongly overlap when folded at right angles to the body and tibio-tarsal articulation reaches beyond the snout tip; femur length less than tibia length (FEL = 14.9 mm; TBL = 18.2 mm); foot length is 1.8 times more than the tarsus length (FOL = 14.9 mm, TAR = 8.1 mm), relative toe length I<II<V<III<IV; tips of toes with truncated enlarged discs having minute dorsoterminal grooves; webbing between toes reduced, webbing just touches the last subarticular tubercle of toe IV and V; inner metatarsal tubercle moderate, bulbous; outer metatarsal tubercle and supernumerary tubercles absent.

Overall skin on the dorsum smooth glandular with scattered small ridged longitudinal glandular folds, folds are discontinuous without any pattern; supratympanic fold distinct; on the ventral side of the body, region of throat smooth and belly glandular.

In life, colour on the dorsum light fleshy brown, base of the raised ridges dark brown and the inter orbital space with light brown blotches; lower lip barred, dark brown streak from the tip of snout till the end of the supratympanic fold in front of shoulders; side of the body uniform light brown without any markings; fore and hind limbs barred; ventrally, region of throat yellowish brown, belly whitish grey and region of thighs flesh-coloured.

In preservative, overall colour on the dorsum grayish brown on the dorsum between the inter-orbital space, horizontal light black band connecting the raised eye balls; upper and lower lips barred; a thin blackish band starting from the tip of snout, through the upper edge of canthus rostralis on either side till the posterior end of the supratympanic fold; sides of the body light gray, raised longitudinal glandular folds dark grey; fore and hind limbs barred; ventrally uniform cream white.

Secondary sexual characters: No visible external sexual dimorphism was noticeable except for the amplected pairs where males are smaller than the females.

Additional information from paratypes and variations: Morphological data are given in Table 1 . Paratype ZSI / WRC /A/2212 ( CESF 1606 ), an adult female ( SVL 44.9 mm) and other reference collections ( CESF 1608 , male, SVL 22.7 mm) were similar to holotype in all the external morphological characters.

Distribution: Walkerana muduga sp. nov. is known from the Elivalmalai range, north of the Palghat Gap and south of Nilgiri Massif.

Comparisons: All the described species of Walkerana are known to occur in the high elevation ranges south of the Palghat Gap. There are no congeners for Walkerana muduga sp. nov. north of the Palghat Gap. However, there is a deeply divergent lineage (CESF 1554) (see diagnosis) recovered from an adjacent massif. Walkerana muduga sp. nov. differs from the undescribed Walkerana sp. (CESF 1554) in having higher HL/SVL ratio of 0.370 to 0.405 (n=2) (vs. lower HL/SVL ratio of 0.342 (n=1)); higher HW/SVL ratio of 0.397 to 0.406 (n=2) (vs. lower HW/SVL ratio of 0.390 (n=1)); lower TYH/SVL ratio of 0.079 to 0.080 (n=2) (vs. higher TYH/SVL ratio of 0.083 (n=1)); higher IO/SVL ratio of 0.107 to 0.109 (n=2) (vs. lower IO/SVL ratio of 0.097 (n=1)); higher PAL/SVL ratio of 0.257 to 0.271 (n=2) (vs. lower PAL/SVL ratio of 0.234 (n=1)); higher f1/SVL ratio of 0.119 to 0.133 (n=2) (vs. lower f1/SVL ratio of 0.112 (n=1)); higher f2/SVL ratio of 0.131 to 0.151 (n=2) (vs. lower f2/SVL ratio of 0.123 (n=1)); lower FEL/SVL ratio of 0.535 to 0.536 (n=2) (vs. higher FEL/SVL ratio of 0.545 (n=1)); lower TAR/SVL ratio of 0.287 to 0.291 (n=2) (vs. higher TAR/SVL ratio of 0.295 (n=1)); higher FOL/SVL ratio of 0.536 to 0.565 (n=2) (vs. lower FOL/SVL ratio of 0.530 (n=1)).

Walkerana muduga sp. nov. differs from species found south of the Palghat Gap (see key to the species of Walkerana by Dahanukar et al. 2016) in having distinct canthus rostralis and smooth skin (vs. indistinct canthus rostralis and warty skin in W. phrynoderma ); lacking a distinct pair of black patches on the loin (vs. distinct black patch on the loin in W. diplosticta ) and tympanum relatively smaller than the diameter of eye (vs. tympanum three-fourth of the diameter of eye in W. leptodactyla ).

Figures

FIGURE 2. Bayesian tree of the genus Walkerana with posterior probability values indicated on the respective nodes.

FIGURE 3. Preserved holotype of Walkerana muduga sp. nov. (A) dorsal view. (B) ventral view.