Leptolalax tamdil, Sengupta & Sailo & Lalremsanga & Das & Das, 2010

Sengupta, Saibal, Sailo, Saipari, Lalremsanga, H. T., Das, Abhijit & Das, Indraneil, 2010, A new species of Leptolalax (Anura: Megophryidae) from Mizoram, North-eastern India, Zootaxa 2406 (1), pp. 57-68 : 60-64

Leptolalax tamdil new species

( Figs. 3–4 )

Leptolalax sp. M.F. Ahmed, A. Das & S.K. Dutta. 2009 Amphib. & Rept. Northeast India: 141.

Holotype: ZSI A10962 (ex MZ 8 ) from Tamdil , 23 o 44.399’N, 92 o 57.313’E, 745 m asl; datum wgs-84), Mizoram State, north-east India. S. Sengupta, S. Sailo, H. T. Lalremsanga and A. Das. 19 April 2007. Adult male.

Paratype: ZSI A10963 (ex MZ 13 ), paratopotype. Adult female with enlarged, unpigmented ova. Collectors and date as above .

Diagnosis: We allocate these specimens to Leptolalax for showing the following characters diagnostic for metamorphosed members (i.e., non-larval characters) of the genus ( Dubois 1980; 1983; 1987 "1986"; Delorme et al. 2006; Malkmus et al. 2002): palpebral projections absent; vomerine teeth absent; finger tips rounded, not disk-like; fingers lacking webbing; basal webbing of toes; limbs relatively long and slender; indistinct subarticular tubercles; inner palmar tubercle does not extend to first metacarpal; low inner metatarsal tubercle; outer metatarsal tubercle absent; nuptial pads absent; presence of macroglands (preaxillary, pectoral, ventrolateral and femoral) on body; bright iris pigmentation mostly restricted to upper orbit and ova unpigmented.

The new species is mid-sized (SVL 32.3 mm in the only male and 31.8 mm in the only female known) species of Leptolalax , diagnosable from congeneric species in showing the following combination of characters: dorsum tuberculate; eyelids with tubercles; tympanum and supratympanic fold distinct; supratympanic fold extending to posterior edge of tympanum; macroglands, including preaxillary, pectorals, femoral femoral and ventrolateral glands present; Finger II> I; toe tips not dilated, bearing dermal fringes; relatively long hind limbs, with heels overlapping when limbs are held perpendicular to body; dorsum with dark blotches; flanks with small dark blotches; dark tympanic mask present; venter pale; labial bars present and limbs with dark cross-bars.

The presence of paired, pale ventrolateral glands and femoral glands in the new species separates it from all members of the southern lineage (subgenus Leptolalax ), including arayai , dringi , gracilis , hamidi , heteropus , kajangensis , kecil , maurus , melanoleucus , nahangensis , pictus and solus (all of which show the absence of both gland types). From members of the northern lineage (subgenus Lalax ), it differs in showing a head wider than long (versus longer than wide, or as wide as long), in addition to the following characters, listed by species (characters in parentheses refer to congener being compared with the new species from Mizoram): from alpinus , eyelids with tubercles, tympanum half orbit diameter and preaxillary gland present (vs. eyelids smooth, tympanum over half orbit diameter and preaxillary gland absent); from applebyi , supratympanic fold distinct, dorsum tuberculate, ventrolateral glandular ridges present and lateral fringes on toes present (vs. head longer than wide, supratympanic fold absent, dorsum smooth, ventrolateral glandular ridges absent and lateral fringes on toes absent); from fuliginosus , eyelids tuberculate, dorsum tuberculate, flanks with small spots and venter unpatterned (vs. eyelids smooth, dorsum smooth, flanks with small spots and venter with dark spots); from liui , snout smooth, dorsum tuberculate, preaxillary gland present and Finger II> I (vs. snout tuberculate, dorsum smooth, preaxillary gland absent and Fingers I and II subequal); from oshanensis , eyelid smooth, tympanum less than half orbit diameter, dorsum bear ridges, toe webbing absent and lateral fringes on toes absent (vs. eyelid tuberculate, tympanum over half orbit diameter, dorsum tuberculate, toe webbing basal and lateral fringes on toes present); from pluvialis , eyelids smooth, dorsum smooth, toe webbing absent and lateral fringes on toes absent (vs. eyelids tuberculate, dorsum tuberculate, toe webbing basal and lateral fringes on toes present); from tuberosus , snout tuberculate, supratympanic fold absent, tympanum absent and Finger I> Finger II (vs. snout smooth, supratympanic fold present, tympanum present and Finger II> Finger I); and from ventripunctatus , eyelid smooth, dorsum ridged, preaxillary glands absent, toe webbing basal and lateral fringes on toes absent (vs. eyelid tuberculate, dorsum tuberculate, preaxillary glands present, toe webbing absent and lateral fringes on toes present).

Additionally, the new species differs from sungi in showing an exposed tympanum, snout smooth, and preaxillary glands present (vs. tympanum covered with skin; snout tuberculate and preaxillary glands absent); from bourreti in showing tympanum greater than half orbit diameter, Finger II> I, weak lateral fringes on toes, and flanks with small spots (vs. tympanum ½-3/5 orbit diameter; Fingers I and II subequal; extensive fringes on toes, and flanks with large spots); from lateralis in showing a smooth snout, tympanum over half orbit diameter, dermal fringes on toes present and flanks with dark spots (vs. snout tuberculate, tympanum less than half orbit diameter, dermal fringes on toes absent and flanks unpatterned) and from pelodytoides , in showing tuberculate eyelids, Finger II> I, and presence of preaxillary glands (vs. eyelids smooth, Fingers I and II subequal, and preaxillary glands absent). The new species from Mizoram differs from khasiorum in showing longer hind limbs, with heels in contact when held perpendicular to body (vs. short hind limbs, with heels widely separated); supratympanic fold terminates at posterior edge of tympanum (vs. continues to insertion of forearm) and abdominal region unpatterned throughout (vs. with dark stippling on lower flanks and lower abdomen). Table 1 lists mensural and meristic data for adults of the genus Leptolalax .

Description of holotype (ZSI A10962; adult male): SVL 32.3 mm; body moderately slender, narrow at waist; cloacal opening at upper level of thighs; head wider than long (HW/HL ratio 1.38); snout obtusely pointed when viewed dorsally and laterally; projecting slightly beyond mandible; palpebral projections absent; nostrils not raised and lack dermal flaps; dorsolaterally positioned, situated slightly below canthus, nearer tip of snout than to eye (E-N/E-S ratio 0.60); internarial distance greater than distance from anterior margin of eye to nostril (IN/E-N ratio 1.18); eye large (ED/HL ratio 0.52); its diameter greater than eye to nostril distance (ED/E-N ratio 1.61); pineal ocellus absent; interorbital space flattened, interorbital width greater than upper eyelid width (IO/UE ratio 1.50); canthus rostralis obtuse; loreal region sloping; no symphysial knob on anterior edge of mandible; mouth extends to beyond posterior corner of eye; choanae located against anterior of palate, visible when viewed from below; vomerine teeth absent; tongue subtriangular, elongate, bifid, free for approximately half its length, lacking papillae and median lingual process; pupil elliptical; tympanum distinct, oval, separated from orbit of eye by a distance 38% of horizontal tympanum diameter; tympanic rim narrow but prominent; supratympanic fold from posterior corner of orbit to above insertion of forelimbs.

Fore limbs short (FL/SVL ratio 0.13); forearm not enlarged; fingers slender, free of web or skin fringes; relative length of fingers: III> II> I> IV; finger tips rounded, not dilated; subarticular tubercles indistinct; outer metacarpal small, elongate, about a third size of rounded inner metacarpal tubercles, the two separated anteriorly by a distinct furrow; inner metacarpal tubercle not extending out under Finger I; nuptial pads absent on fingers.

Hind limbs long (TBL/SVL ratio 0.49); heels in contact when hind limbs are flexed and held perpendicular to body; toe- tips weakly differentiated, not truncate apically; distinct lateral fringes present on inner aspects of all toes; toes webbed up to base of phalanges; relative length of toes: 4> 3> 5> 2> 1; subarticular tubercles indistinct; distinct ridges on undersurfaces of toes; no outer metatarsal tubercle; a large, compressed inner metatarsal tubercles; keratinized dermal ridges replace subarticular tubercles, covering entire undersurfaces of toes.

Dorsum weakly tuberculate, with low, oval tubercles, those on flanks not differentiated; snout smooth; upper eyelids with small tubercles; vocal sac indistinct on throat; vocal opening close to rictus; sacral region and dorsal surfaces of thigh and tibia with low tubercles; tarsal fold present; gular, pectoral, abdominal regions, undersurfaces of forelimbs, shanks and thighs smooth; macroglands present include small, oval preaxillary glands (largest axis = 0.9 mm) in front of forearm; large (1.7 mm), oval, flattened pectoral glands at insertion of forearms; elongate (8.1 mm) ventrolateral glands on lower flanks; large (1.1 mm), oval femoral glands on lower half of femur, closer to knees than to vent; small (1.2 mm) paired, oval, preanal glands below vent; low tubercle project over vent.

Colour: In life, forehead and dorsum mid-grey, with irregular dark grey blotches; an inverted, hourglassshaped dark grey blotch in interorbital region; flanks with blackish-grey blotches that partially encircle pale tubercles; lower tympanum grey, with a large brown mask covering top three-fourths up to supratympanic fold; dark greyish-black stripe across rostral region, along snout-tip; top third of iris bright orange, rest of iris greyish-cream, edged peripherally with irregular black radiating lines; labials with greyish-black bars; tubercles on dorsum and hind limbs pale; preaxillary gland orange; upper surfaces of fore and hind limbs midgrey with dark grey bands; phalanges pale grey with dark grey crossbars; dorsal surfaces of Fingers I–II distinctly paler than those of Fingers III–IV; undersurfaces of forearm, anterior edge of thighs and shanks with distinct dark grey variegation; undersurfaces of thighs dark grey with cream coloured oval spots; hand and feet mid-grey; gular and abdominal regions pale grey, lacking scattered dark grey pigments; abdominal region unpatterned cream; pectoral, ventrolateral and femoral glands pale in preservative (colour of macroglands in life unrecorded); pale preanal glands.

Measurements: Mensural data of the two types (ZSI A10962 and A10963 , respectively) are given below, in mm: SVL 32.3 and 31.8, IN 3.2 and 3.1, HL 8.7 and 8.8, HW 12.0 and 12.0, HD 5.2 and 4.8, ED 4.5 and 4.6, IO 5.1 and 5.8, E-S 4.7 and 4.7, E-N 2.8 and 2.7, E-T 1.1 and 1.4, UE 3.4 and 3.5, HTD 2.9 and 3.1, VTD 2.3 and 2.2, FL 4.3 and 3.5, TBL 16.0 and 15.7, IMT 1.9 and 1.8, IPT 2.2 and 1.8, A-G 13.8 and 13.8 and BW 9.7 and 11.9.

Etymology: Named for the type locality of Tamdil (literally, 'The Lake of the Mustard Plant' in the Mizo language), a lake of national importance in Mizoram State (formerly, the Lushai Hills of Assam State), northeastern India.

Ecological notes: The type locality of Tamdil, a natural lake situated ca. 110 km south-east of the state capital of Aizawl ( Fig. 1 ), is a wetland covered by the National Wetland Conservation Programme 2006– 2007, of the Government of India. A 285 ha area is protected for wetland functions (Anon. 2007). The region lies within the subtropical belt, receiving heavy (ca. 254 cm /annum) precipitation associated with the Southwest Monsoons (between May and September), and summer and winter temperature ranges are 20– 29°C and 11–21°C (Anon. 2008). The presence of large eggs (unpigmented, measuring ca. 2.2–2.3 mm) in the paratype is suggestive of spring breeding in the new species.

Tamdil Lui , the stream where sampling took place, is surrounded by tropical evergreen and moist deciduous forest dominated by Schima wallichii, Chukrasia tabularis, Albizzia sp., Artocarpus sp. and Merus sp. Champion and Seth (1968) 's phytogeographic classification places the areas in the “C2. Cachar Tropical Semi-evergreen Forest” category. The type series were collected at ca. 2130 h, from under small rocks of a slow-flowing stream ( Fig. 2 ). Other frogs found in sympatry include Amolops gerbillus, Euphlyctis cyanophlyctis, Ingerana borealis, Hylarana sp., Clinotarsus alticola, Microhyla ornata, Xenophrys sp. , Chirixalus vittatus , Polypedates teraiensis / leucomystax species complex member, Polypedates sp. and Fejervarya spp.

Figures

FIGURE 1. Map of India and adjacent countries of south Asia inset showing enlarged area of north-eastern India enlarged, which shows the type locality of Leptolalax tamdil sp. nov. at Tamdil, Mizoram State.

FIGURE 2. Habitat of Leptolalax tamdil sp. nov. at Tamdil, Mizoram State, north-eastern India.

FIGURE 3. Male holotype of Leptolalax tamdil sp. nov. (ZSI A10962), in life (A), as well as preserved, in dorsal (B) and ventral (C) views.

FIGURE 4. Holotype of Leptolalax tamdil sp. nov. (ZSI A10962), showing right side of venter (A) and the distribution of macroglands; right hand (B) and feet (C). References: P = Pectoral glands; V = Ventrolateral glands; F = Femoral glands.