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

Nyctibatrachus radcliffei sp. nov.

urn:lsid:zoobank.org:act:0F9F1491-B1E0-4F4B-9946-0E21AA7E71C8

Radcliffe’s Night Frog

(Figs. 1 and 6; Tables S1–S7)

Holotype. ZSI/WGRC/V/A/920, adult male, from Thiashola estate (11°13 48.2 N 76° 37 0 2.1 E, 1920 m), Nilgiris district, Tamil Nadu state, India, collected by SDB and SG on 0 9 July 2016.

Paratypes. ZSI/WGRC/V/A/921–922, two adult males, collected along with the holotype, and ZSI/WGRC/V/A/923–924, two adult males, collected from the same locality as holotype, by SDB and SG on 0 8 July 2016.

Other material studied. SDBDU 2014.2771, from the same locality as the type series, collected by SDB and SG on 0 6 October 2014, was used only for genetic identification of species.

Etymology. This species is named after the late Major Richard Radcliffe in recognition of his contribution towards biodiversity conservation in the Nilgiris. The species name radcliffei is a noun in the genitive case.

Diagnosis. Nyctibatrachus radcliffei can be distinguished from known congeners by the following combination of morphological characters: (1) medium-sized adult males (SVL 32.8–38.3 mm, N = 5); (2) body robust; (3) a well developed ridge extending from the lip over the tip of the snout to between the nostrils, at which point it bifurcates, producing an inverted ‘Y’; (4) wrinkled dorsal skin without prominent spinular projections; (5) third finger disc prominent (male FDIII 1.0–1.2, FWIII 0.4–0.6, N = 5), without dorso-terminal groove; (6) fourth toe disc prominent (male TDIV 1.5–1.6, TWIV 0.5–0.6, N = 5), with dorso-terminal groove and cover rounded distally; (7) presence of two palmar tubercles; (8) foot webbing large, fourth toe webbing extending up to the disc on either side; (9) thigh longer than shank (male TL/SHL ratio 107.1–110.2%, N = 5); and (10) shank nearly equal to foot length (male SHL/FOL ratio 97.6–102.9%, N = 5).

Morphological comparison. Nyctibatrachus radcliffei can be distinguished from its congeners N. aliciae, N. anamallaiensis, N. athirappillyensis sp. nov., N. beddomii, N. deccanensis, N. deveni, N. kempholeyensis, N. manalari sp. nov., N. minimus, N. minor, N. periyar, N. pillaii, N. pulivijayani sp. nov., N. robinmoorei sp. nov., N. sabarimalai sp. nov., N. shiradi, N. vasanthi and N. webilla sp. nov. by its larger adult male snout-vent size, SVL 32.8–38.3 mm (vs. smaller, male SVL 10.0–27.6 mm); differs from N. karnatakaensis and N. kumbara by its smaller adult male snout-vent size, SVL 32.8–38.3 mm (vs. larger, male SVL 42.8–63.8 mm); differs from N. danieli, N. dattatreyaensis, N. humayuni, N. jog, N. petraeus, N. poocha, N. sanctipalustris and N. vrijeuni by its fourth toe webbing extending up to the disc on either side (vs. not beyond the first subarticular tubercle on either side), third finger disc without groove, and fourth toe disc with dorso-terminal groove and cover rounded distally (vs. third finger disc with dorso-terminal groove and cover rounded distally in N. danieli; fourth toe disc with dorso-terminal groove and cover notched distally in N. dattatreyaensis; third finger disc with dorso-terminal groove and cover rounded distally in N. humayuni, N. jog and N. petraeus; third finger disc and fourth toe disc with dorso-terminal groove and cover bifurcate distally in N. poocha; fourth toe disc with dorso-terminal groove and cover notched distally in N. sanctipalustris and N. vrijeuni). Because of its extensive webbing between toes, third finger and fourth toe disc morphology, and wrinkled dorsal skin, Nyctibatrachus radcliffei could be confused with N. acanthodermis, N. gavi, N. grandis, N. major and N. sylvaticus. Nyctibatrachus radcliffei may also be confused with N. indraneili, which occurs in the same geographical region in the Nilgiris. However, N. radcliffei differs from N. acanthodermis by its dorsal skin without prominent spinular projections (vs. prominent wrinkled skin with spinular projections), relatively smaller male snout-vent size, SVL 32.8–38.3 mm, N = 5 (vs. larger, male SVL 52.9–66.2 mm, N = 4), relatively larger male SL/HL ratio of 43.8–47.2%, N = 5 (vs. male SL/HL ratio of 32.8–37%, N = 4), relatively larger male EL/HL ratio of 26.5–32.2%, N = 5 (vs. male EL/HL ratio of 21.6–22.8%, N = 4), thigh longer than shank, male TL/SHL ratio 107.1–110.2%, N = 5 (vs. nearly equal, male TL/SHL ratio 99.3–100.3%, N = 4), shank nearly equal to foot length, male SHL/FOL ratio 97.6–102.9%, N = 5 (vs. longer, male SHL/FOL ratio 106.7–110.3%, N = 4), and fourth toe webbing extending up to the disc on either side, I1–1II1–1+III1–1+IV1–1V (vs. below, I1–1II1–1+III1–1 2/3IV1 2/3–1V).

Nyctibatrachus radcliffei differs from N. gavi by its snout rounded in lateral view (vs. nearly obtuse), relatively smaller male snout-vent size, SVL 32.8–38.3 mm, N = 5 (vs. larger, male SVL 49.5–57.5 mm, N = 2), relatively larger male SL/HL ratio of 43.8–47.2%, N = 5 (vs. male SL/HL ratio of 32.5–34.3%, N = 2), relatively smaller male FAL/HAL ratio of 61.6–69.5%, N = 5 (vs. male FAL/HAL ratio of 72.1–81.5%, N = 2), and fourth toe webbing extending up to the disc on either side, I1–1II1–1+III1–1+IV1–1V (vs. up to the first subarticular tubercle on either side: I1–1 2/3II1–1 3/4III1–2IV2–1V).

Nyctibatrachus radcliffei differs from N. grandis by its relatively smaller male snout-vent size, SVL 32.8–38.3 mm, N = 5 (vs. larger, male SVL 62.2–76.9 mm, N = 3), relatively smaller male HL/SVL ratio of 35.2–37.2%, N = 5 (vs. male HL/SVL ratio of 39.3–40.3%, N = 3), relatively larger male SL/HL ratio of 43.8–47.2%, N = 5 (vs. male SL/HL ratio of 34.5–36.3%, N = 3), and fourth toe webbing extending up to the disc on either side, I1–1II1–1+III1–1+IV1–1V (vs. below, I1–1II1–1 3/4III1–1 3/4IV1 3/4–1V).

Nyctibatrachus radcliffei differs from N. indraneili by its wrinkled dorsal skin (vs. weakly wrinkled), relatively smaller male snout-vent size, SVL 32.8–38.3 mm, N = 5 (vs. larger, male SVL 42.5, N = 1), relatively larger male SL/HL ratio of 43.8–47.2%, N = 5 (vs. male SL/HL ratio of 33.3%, N = 1), eye length shorter than snout length, male EL/SL ratio 58.1–73.6%, N = 5 (vs. equal, male EL/SL ratio 100%, N = 1), fourth toe disc with dorso-terminal groove and cover rounded distally (vs. without groove), and fourth toe webbing extending up to the disc on either side, I1–1II1–1+III1–1+IV1–1V (vs. below, I1–1II1–2III1–2−IV2−–1V).

Nyctibatrachus radcliffei differs from N. major by its relatively larger male SL/HL ratio of 43.8–47.2%, N = 5 (vs. male SL/HL ratio of 34.3–41%, N = 7), relatively smaller male FAL/HAL ratio of 61.6–69.5%, N = 5 (vs. male FAL/HAL ratio of 74.6–86.9%, N = 7), thigh longer than shank, male TL/SHL ratio 107.1–110.2%, N = 5 (vs. nearly equal, male ratio TL/SHL 99.5–101.3%, N = 7), and fourth toe webbing extending up to the disc on either side, I1–1II1–1+III1–1+IV1–1V (vs. up to the first subarticular tubercle on either side, I1 1/3–1 3/4II1–2 1/3III1–2IV2–1V).

Nyctibatrachus radcliffei differs from N. sylvaticus by its relatively larger male SL/HL ratio of 43.8–47.2%, N = 5 (vs. male SL/HL ratio of 35.8–37.7%, N = 4), relatively smaller male FAL/HAL ratio of 61.6–69.5%, N = 5 (vs. male FAL/HAL ratio of 76.3–79.7%, N = 4), and fourth toe webbing extending up to the disc on either side, I1–1II1–1+III1–1+IV1–1V (vs. up to the first subarticular tubercle on either side, I1–1 4/5II1–2III1–2IV2–1V).

Description of holotype (measurements in mm). Adult male (SVL 38.3); head wider than long (HW 14.5, HL 13.6); snout nearly rounded in dorsal view, rounded in lateral view, its length (SL 6.2) longer than horizontal diameter of eye (EL 3.6); loreal region obtuse with indistinct canthus rostralis; interorbital space flat, wider (IUE 3.8) than upper eyelid (UEW 2.3) and internarial distance (IN 2.9); nostril closer to eye (EN 2.6) than tip of snout (NS 3.3); tympanum indistinct; vomerine ridge present, bearing small teeth, at an angle of 90° to the body axis, closer to each other than choanae, longer than the distance between them; tongue moderately large, emarginated, bearing no median lingual process. Forearm (FAL 6.9) shorter than hand length (HAL 11.2), finger length formula: I <II <IV <III, fingers with prominent discs, finger discs wide compared to finger width (FDI 1.2, FWI 0.6; FDII 1.2, FWII 0.5; FDIII 1.2, FWIII 0.4; FDIV 1.0, FWIV 0.4), tips rounded without groove; subarticular tubercles prominent, oval, single, all present; prepollex distinct, oval; two palmar tubercles, oval, distinct; nuptial pads present. Thigh length (TL 18.5) longer than shank (SHL 17.1) and foot (FOL 17.1), relative digit lengths I <II <III <V <IV, toes with prominent discs, toe discs wide compared to toe width (TDI 1.5, TWI 0.5; TDII 1.6, TWII 0.6; TDIII 1.6, TWIII 0.6; TDIV 1.6, TWIV 0.6; TDV 1.2, TWV 0.5), toes discs with dorso-terminal groove, cover rounded distally; foot webbing large: I1–1II1–1+III1–1+IV1–1V, fourth toe webbing extending up to the disc on either side; subarticular tubercles well developed, oval, single, all present; inner metatarsal tubercle present, oval; outer metatarsal tubercle absent; dermal fringe along toes I and V present; a tarsal fold extending from anterior edge of the inner metatarsal tubercle.

Skin of snout shagreened to granular, upper eyelids tuberculate; sides of the head, anterior and posterior parts of back, and upper and lower parts of flank wrinkled; subocular gland prominent, extending from the posterior ventral border of the orbit towards the posterior axis of the mandibles; supratympanic fold well developed, extending from behind the eye to near the shoulder; dorsal parts of forelimb, thigh and shank with weakly developed folds or wrinkles; a well developed ridge starting from the lip and extending over the tip of the snout to between the nostrils, at which point it bifurcates, producing an inverted ‘Y’; ventral surface of throat with longitudinal folds, chest shagreened, belly shagreened to slightly wrinkled, limbs shagreened; femoral glands weakly developed.

Colour of holotype. In life. Dorsum and lateral sides of head reddish-brown with scattered blackish-brown spots, upper eyelids dark brown (Figs. 6 A and 6B); forelimbs (including fingers) and hind limbs (including toes) light brown with faint brown transverse bands; anterior and posterior parts of flanks light brown. Ventral surfaces light flesh-red, sides of abdomen and hind limbs light reddish-brown with prominent black speckles; hand and foot dark grey; foot webbing light grey with minute black speckles (Fig. 6 E). In preservation. Dorsum and lateral sides of head dark grey with scattered black spots, upper eyelids dark grey (Fig. 6 F); ventral surfaces greyish-white, sides of abdomen and limbs grey with dark grey spots; hand and foot dark grey (Figs. 6 G and 6H).

Variations. Morphometric data from five adult males, including the holotype, is given in Table S6. Overall, the colour and meristic characters of the paratypes are similar to the holotype. Colour in preservation. ZSI/WGRC/V/A/921, ZSI/WGRC/V/A/923–924: dorsum uniformly darker brown in colour, ventral surface with more prominent greyishbrown speckles.

Secondary sexual characters. Male (ZSI/WGRC/V/A/920), femoral glands weakly developed, nuptial pads absent.

Distribution and natural history. Nyctibatrachus radcliffei sp. nov. is currently known only from its type locality, which is located in the Nilgiris, north of Palghat gap in the southern Western Ghats state of Tamil Nadu. All the specimens were found in crevices under rocks in a hill stream inside the tea estate. In our study, we observed tadpoles of this species during the month of October 2014 and confirmed their identity using DNA. Since calls or breeding activity was not observed at the time of collection (in July), we presume that this species breeds during the early monsoon period. Collections were made between 20:00–23:00 h.