Nyctibatrachus robinmoorei Garg, Suyesh, Sukesan & Biju, 2017, sp. nov.

Nyctibatrachus robinmoorei sp. nov.

urn:lsid:zoobank.org:act:DB413903-56B5-4D36-93B4-ABA3555CC99F

Robin Moore’s Night Frog

(Figs. 1 and 7; Tables S1–S7)

Holotype. ZSI/WGRC/V/A/925, adult male, from Kakkachi (08°33 0 2.6 N, 77°23 29.6 E, 1290 m), Tirunelveli district, Tamil Nadu state, India, collected by SDB on 30 August 2002. Paratype. ZSI/WGRC/V/A/926, adult female, collected along with the holotype.

Referred specimen. SDBDU 2002.312, adult male, collected along with the holotype. Etymology. The species is named for Dr Robin Moore, a wildlife photographer and conservationist, in appreciation of his contribution to amphibian conservation. The species name robinmoorei is considered as a noun in the genitive case.

Diagnosis. Nyctibatrachus robinmoorei can be distinguished from known congeners by the following combination of morphological characters: (1) miniature-sized adult males (SVL 12.2–13.4 mm, N = 2); (2) head width nearly equal to head length (male HW/HL ratio 97.6–100%, N = 2); (3) presence of weakly developed dorsolateral glandular folds separated by scattered granular projections; (4) third finger disc slightly wider than finger width (male FDIII 0.4–0.5, FWIII 0.3–0.4, N = 2), with dorso-terminal groove and cover bifurcate distally; (5) fourth toe disc slightly wider than toe width (male TDIV 0.5–0.6, TWIV 0.3, N = 2), with dorso-terminal groove and cover bifurcate distally; (6) presence of single palmar tubercle; (7) foot webbing absent; (8) forearm longer than hand length (male FAL/HAL ratio 105.3–111.8%, N = 2); (9) thigh longer than shank length (male TL/SHL ratio 127.5–130.8%, N = 2); and (10) thigh longer than foot length (male TL/FOL ratio 122.6–130.8%, N = 2).

Morphological comparison. Nyctibatrachus robinmoorei can be distinguished from all its congeners, expect N. anamallaiensis, N. athirappillyensis sp. nov., N. beddomii, N. deccanensis, N. kempholeyensis, N. manalari sp. nov., N. minimus, N. minor, N. pulivijayani sp. nov., N. sabarimalai sp. nov. and N. webilla sp. nov., by its smaller male snout-vent size, SVL 12.2–13.4 mm (vs. male SVL 18.1–76.9 mm), absence of webbing between Garg et al. (2017), PeerJ, DOI 10.7717/peerj.3007 28/50 toes (vs. present) and dorsal skin not prominently wrinkled and/or granular (vs. prominently wrinkled and/or granular); differs from N. athirappillyensis, N. deccanensis and N. kempholeyensis by absence of webbing between toes (vs. present); differs from N. minor by its dorsal skin without distinct dorsolateral glandular folds separated by an ‘X’ pattern on anterior half of back (vs. present); and differs from N. webilla by its third finger disc with dorso-terminal groove and cover bifurcate distally (vs. without dorso-terminal groove).

Because of the comparable snout-vent size, Nyctibatrachus robinmoorei could be confused with three previously known species N. anamallaiensis, N. beddomii and N. minimus, and three new species N. manalari, N. pulivijayani and N. sabarimalai. However, N. robinmoorei differs from N. anamallaiensis by its head nearly as wide as long, male HW/HL ratio 97.6–100%, N = 2 (vs. head wider than long, male HW/HL 115.7–126.1%, N = 5), eye length shorter than snout length, male EL/SL ratio 71.4–75%, N = 2 (vs. longer, male EL/SL ratio 125–140%, N = 5), forearm longer than hand length, male FAL/HAL ratio 105.3–111.8%, N = 2 (vs. shorter, male FAL/HAL ratio 72.7–83.3%, N = 5), and thigh longer than shank, male TL/SHL ratio 127.5–130.8%, N = 2 (vs. nearly equal, male TL/SHL ratio 98.4–101.6%, N = 5).

Nyctibatrachus robinmoorei differs from N. beddomii by its dorsolateral glandular folds separated by scattered granular projections (vs. dorsal skin finely granular), head nearly as wide as long, male HW/HL ratio 97.6–100%, N = 2 (vs. head wider than long, male HW/HL 106.6–129.3%, N = 10), and thigh longer than shank, male TL/SHL ratio 127.5–130.8%, N = 2 (vs. nearly equal, male TL/SHL ratio 95.9–101.6%, N = 10).

Nyctibatrachus robinmoorei differs from N. minimus by its dorsolateral glandular folds separated by scattered granular projections (vs. dorsal skin with faint and interrupted glandular folds), forearm longer than hand length, male FAL/HAL ratio 105.3–111.8%, N = 2 (vs. shorter, male FAL/HAL ratio 69–82.9%, N = 14), and thigh longer than shank, male TL/SHL ratio 127.5–130.8%, N = 2 (vs. nearly equal, male TL/SHL ratio 95.9–101.6%, N = 14).

Nyctibatrachus robinmoorei differs from N. sabarimalai by its head nearly as wide as long, male HW/HL ratio 97.6–100%, N = 2 (vs. head longer than wide, male HW/HL 82.4– 89.8%, N = 5), forearm longer than hand length, male FAL/HAL ratio 105.3–111.8%, N = 2 (vs. shorter, male FAL/HAL ratio 85.7–96.6%, N = 5), thigh longer than shank length, male TL/SHL ratio 127.5–130.8%, N = 2 (vs. nearly equal, male TL/SHL ratio 98.4–101.6%, N = 5), and thigh longer than foot length, male TL/FOL ratio 122.6–130.8%, N = 2 (vs. nearly equal, male TL/FOL ratio 96.9–101.6%, N = 5).

For differences with Nyctibatrachus manalari and N. pulivijayani see comparison of those species.

Description of holotype (measurements in mm). Adult male (SVL 12.2); head small, head width subequal to head length (HW 4.0, HL 4.1); snout rounded in dorsal and lateral views, its length (SL 2.0) longer than horizontal diameter of eye (EL 1.5); loreal region obtuse with indistinct canthus rostralis; interorbital space flat, wider (IUE 1.9) than upper eyelid (UEW 0.6) and internarial distance (IN 1.5); nostril closer to eye (EN 1.0) than the tip of snout (NS 1.3); tympanum indistinct; vomerine ridge present, bearing small teeth, at an angle of 85° to the body axis, closer to each other than choanae, longer than the distance between them; tongue emarginated, bearing no median lingual process. Forearm (FAL 1.9) longer than hand length (HAL 1.7), finger length formula: I <II = IV <III, finger discs slightly wide compared to finger width (FDI 0.3, FWI 0.2; FDII 0.3, FWII 0.2; FDIII 0.4, FWIII 0.3; FDIV 0.3, FWIV 0.2), finger disc with dorso-terminal groove, cover bifurcate distally; subarticular tubercles prominent, oval, single, all present; prepollex distinct, oval; single palmar tubercle, oval, distinct; nuptial pads present. Thigh (TL 6.5) longer than shank (SHL 5.1) and foot (FOL 5.3), relative toe lengths I <II <V <III <IV, toe discs slightly wide compared to toe width (TDI 0.3, TWI 0.2; TDII 0.3, TWII 0.2; TDIII 0.5, TWIII 0.3; TDIV 0.5, TWIV 0.3; TDV 0.3, TWV 0.2), toe discs with dorso-terminal grooves, cover bifurcate distally; foot webbing absent; subarticular tubercles well developed, oval, single, all present; inner metatarsal tubercle present, oval; outer metatarsal tubercle weakly developed. Skin of snout shagreened to sparsely granular, upper eyelids with a few prominent glandular warts especially on the margins, presence of weakly developed dorsolateral glandular folds separated by granular projections; sides of the head, anterior and posterior parts of back, and upper and lower parts of flank shagreened with scattered glandular projections; upper surface of arms and legs with minute granular projections; ventral surfaces smooth; a pair of prominent femoral glands present on the ventral surface of thighs (Fig. 7 F).

Colour of holotype. In life. Dorsum reddish-brown, with a pair of light orangish-brown longitudinal bands starting from behind the eyelids and extending up to the middle of dorsum (Fig. 7 C), another light orangish-brown stripe between the eyes demarcating a triangular light orangish-brown patch on the snout; lateral sides of the head dark greyishbrown with scattered minute black speckles and prominent white spots, upper eyelids dark greyish-brown (Fig. 7 C); upper and lower parts of flank light brown with scattered white spots (Fig. 7 A); forelimbs (including fingers) and hind limbs (including toes) light brown with faint dark grey transverse bands. Ventral surfaces light grey with prominent minute black spots, hand and foot darker in colour (Fig. 7 F). In preservation. Dorsum brown, with a pair of light brown longitudinal bands starting from behind the eyelids and extending up to the middle of dorsum, another light brown stripe between the eyes demarcating a triangular light brown patch on the snout; upper eyelids dark grey; forelimbs (including fingers) and hind limbs (including toes) light greyish-brown with faint grey transverse bands; anterior and posterior parts of flanks light greyish-brown. Ventral surfaces light greyish-white with minute dark grey spots.

Variations. Morphometric data from two adult males and an adult female, including the holotype, is given in Table S6. Overall, the colour, markings and meristic characters of the paratype and referred specimen are similar to the holotype.

Secondary sexual characters. Male (ZSI/WGRC/V/A/925), femoral glands present, nuptial pads present; female (ZSI/WGRC/V/A/926), small pigmented eggs present (diameter 1.7 ± 0.3mm, N = 15).

Distribution and natural history. Nyctibatrachus robinmoorei is currently known only from its type locality, which is located in the Kalakkad Mundanthurai Tiger Reserve, south of Palghat gap in the Western Ghats state of Tamil Nadu. Animals were collected from a marshy area covered with thick ground vegetation, close to a rivulet inside primary forest.

Males were heard calling during daytime (12:00–14:00 h) and in the late evening (around 18:00 h).