Leptobrachium aryatium Purkayastha, Dutta, Gogoi & Sengupta, 2025, sp. nov.

Leptobrachium aryatium sp. nov. Fig. 3–5, 12 Holotype: Adult male ([ADBUA1085]; Fig. 3), from Garbhanga Reserve Forest (26.065892°N, 91.752645°E; elevation 230 m a.s.l.), Kamrup Metropolitan District, Assam, India collected on 14 June 2004 by Saibal Sengupta Paratypes (Fig. 4). Two adult males (ADBUA1084 and ADBUGRB6982) and one adult female (ADBUA0474), same collection details as holotype except for the collection date of ADBUA0474 was on 4 April 2005. Diagnosis Leptobrachium aryatium sp. nov. can be distinguished from other congeners by the following combination of morphological characteristics: A medium-sized species with adult SVL of 49.0– 55.4 mm in males and 53.2–61.65 mm in females; head wider than long; iris bicoloured, top 1/4th fiery orange with gradually thinning in the middle becoming inverted “V” shaped and the rest is black in colour, with bright-blue sclera; nostril closer to the snout than to the eyes; tympanum indistinct; supratympanic fold distinct extending from behind eye to arm insertion; relative finger lengths: I<IV<II<III; relative toe lengths: I<II<V<III<IV; toe webbing formula: I 0–1 II 0–2 III 0–3 IV 3–1/2 V; large inner and outer metacarpal tubercle present, inner metatarsal tubercle large and spade shaped; dorsal skin sparsely tuberculated with lateral region having most tubercles; dorsum in shades of light to dark uniform grey with prominent black spots, elongated in the lateral region than on the vertebral region; ventrum creamy to white with varying amount of dark infusion.; gular region with prominent black reticulation pattern; dark marking covering the entire tympanum; dark canthal stripe present; dorsal part of tibia with prominent dark blotches forming 4–5 rows; dark blotch at groin present, posterior sides of thighs blackish with white spots; males with a single vocal sac. Comparison The colour of iris and scleral ring are important diagnostic feature in identification of the species within the genus Leptobrachium (Matsui et al. 1999; Hamidy & Matsui 2014; Stuart et al. 2011; Wogan 2012; Yang et al. 2016; Pawangkhanant et al. 2018; Al-Razi et al. 2021) Leptobrachium aryatium sp. nov. has a bicoloured iris having upper 1/4 th fiery orange with a typical getting thinner at the middle becoming inverted “ V ” shaped and the rest is black in colour, with bright-blue sclera versus black or dark-brown in L. abbotti (Cochran), L. chapaense Bourret, L. gunungense Malkmus, L. hasseltii, L. ingeri Hamidy, Matsui, Nishikawa & Belabut, L. kanowitense Hamidy, Matsui, Nishikawa & Belabut, L. kantonishikawai Hamidy & Matsui, L. lumadorum Brown, Siler, Diesmos & Alcala, L. mangyanorum Brown, Siler, Diesmos & Alcala, L. montanum, L. nigrops Berry & Hendrickson and L. tagbanorum Brown, Siler, Diesmos & Alcala; black and white or black and blue in L. ailaonicum (Yang, Chen & Ma), L. banae Lathrop, Murphy, Orlov & Ho, L. boringii Lui, L. buchardi Ohler, Teynié & David, L. guangxiense, L. hainanense Ye & Fei, L. huashen Fei & Ye, L. leishanense (Liu & Hu), L. leucops Stuart, Rowley, Tran, Le & Hoang, L. liui Pope, L. masatakasatoi Matsui, L. ngoclinhense Orlov, L. promustache (Rao, Wilkinson & Zhang), L. tenasserimense, L. xanthop Stuart, Phimmachak, Seateun & Sivongxay and L. xanthospilum Lathrop, Murphy, Orlov & Ho; blue in L. bompu Sondhi & Ohler and L. waysepuntiense Hamidy & Matsui; reddish or orange scleral ring in L. lunatum Stuart, Som, Neang, Hoang, Le, Dau, Potter & Rowley, L. mouhoti Stuart, Sok & Neang and L. pullus Smith. Leptobrachium aryatium sp. nov. differs from L. hendricksoni Taylor by having dorsum in shades of light to dark uniform grey with prominent black spots versus lavender brown dorsum without any distinct marks, presence of head markings versus absent or indefinite. Leptobrachium aryatium sp. nov. is a member of L. smithi species complex (see Al-Razi et al. 2021) and thus a close comparison with the member species namely L. rakhinense, L. smithi, L. sylheticum and L. tenasserimense is most relevant for species delimitation. Leptobrachium aryatium sp. nov. differs from L. sylheticum in having obscured tympanum (versus distinct), head little longer than broad, HW/HL: 0.997 (versus wider than long; HW/ HL: 1.159), relative toe length I<II<V <III <IV (versus V <I=II<III <IV), toe web I 0-1 II 0-2 III 0-3 IV 3-½ V (versus I 1-1 II 1-2 III 1-3¼ IV 3½-1 V), inner metatarsal tubercle spade shaped (versus elongated), iris bicoloured, upper ¼ th fiery orange (versus upper ⅓ rd fine red), dorsal side of the body uniformly light to dark grey with prominent black spots/ small blotches (versus dorsum uniform grey with few black spots laterally), lateral side of the body has elongated black patches frequently forming rows (versus laterally may have few black spots without forming rows), ventrally belly creamy to white with varying amounts of dark infusion (versus belly dark grey to black with irregular sparse whitish marbling on chest and anterior part), orange red dots absent, gular with prominent black reticulation (versus tiny orange red dots on lower jaw and gular area), strong supratympanic fold, flanked by dark stripe/blotch (versus distinct supratympanic fold, without dark flank), dorsal part of tibia with 4 – 5 rows of dark markings (vs 2–3 rows of dark markings), groin with dark blotch (versus without blotch); from L. rakhinense in possessing bicoloured iris, upper half fiery orange (versus upper half of iris red), a strong supratympanic fold (versus supratympanic fold is weak), relative finger length II ≤ I <IV <III (vs II <IV <I <III), toe web I 0-1 II 0-2 III 0-3 IV 3-½ V (versus I 1 ½-3 II 1-3 III 2-3½ IV 4-3 V), irregular dark blotches, a ‘Y shaped’ mark may or may not be present, when present this may be complete or broken, bordered with a dark brown rim (versus an inverted ‘Y shaped’ mark on the head without dark rim), the dorsal blotches are without white outline (blotches are outlined with white), dorsal blotches are irregularly arranged (versus another ‘Y shaped’ mark begins just posterior to the eyes and broadens between shoulders), ventrum whitish and speckled heavily with dark markings (versus light colour with small white speckles), eggs are bicoloured (versus unicoloured); from L. tenasserimense in having head little longer than wide HW/HL: 0.98 (versus slightly wider than long HW/HL: 1.029), iris upper half fiery orange (versus bluish green), tympanic hidden (versus distinct), relative finger length II ≤ I <IV <III (versus II <IV <I <III), ventrolateral row of dark spots present (versus absent), strong supratympanic fold (versus weak supratympanic fold). From L. smithi by having obscured tympanum (versus distinct tympanum), broad tongue which is entire posteriorly (versus tongue notched posteriorly), toe web I 0-1 II 0-2 III 0-3 IV 3-½ V (versus I 1-3 II 2½ - 1 III 2 – ½ IV 2-1 V), larval labial tooth formula 1:5+5/5+5:1 (versus 1: 6+6/5+5:1). Furthermore, the advertisement call of Leptobrachium aryatium sp. nov. exhibits distinct characteristics when compared to its closely related species, L. smithi and L. sylheticum. One note of Leptobrachium aryatium sp. nov. has a duration of approximately 0.5 seconds, with a frequency range spanning 0.5–5 kHz and a dominant frequency centred around 1–2 kHz. The amplitude pattern is characterized by a gradual rise to a peak and subsequent tapering, giving it a smoother temporal structure. In comparison, one note of L. smithi has a duration of approximately 1.0 seconds (see Matsui et al. 1999) displays a broader frequency range of 1–6.5 kHz, with dominant energy concentrated between 2–3 kHz. The amplitude pattern of L. smithi is highly symmetrical, with a sharp rise and fall around the midpoint of the call. This contrasts with the smoother amplitude pattern observed in Leptobrachium aryatium sp. nov.. One note of L. sylheticum has a duration of approximately 0.3 seconds (see Al-Razi et al. 2021) with a frequency range of 0.5–4 kHz and a dominant frequency around 2 kHz. The amplitude pattern of L. sylheticum is more variable, displaying multiple peaks and valleys within its short call duration. These acoustic differences, particularly in call duration, frequency range, dominant frequency, and amplitude pattern, clearly differentiate Leptobrachium aryatium sp. nov. from L. smithi and L. sylheticum, supporting its recognition as a distinct species. Description of holotype Adult male in a good state of preservation, with SVL 54.0 mm; Head large, broad and flattened, almost as broad as long (HWAJ/HL: 0.94), snout gently rounded, gently sloping in profile, projecting beyond lower jaw; nostrils round, oriented dorsally, located on the canthus rostralis, closer to tip of snout than to eye (NS/EN: 0.38); canthus rostralis distinct, rounded; loreal region deeply concave; internarial distance less than half of the interorbital distance; eyes very large, bulging, distinctly projecting from sides of head in lateral and dorsal view, eye diameter one third of the snout length (ED/SL: 75); interorbital distance almost twice the upper eyelid width (UE/IOS: 0.52); tympanum indistinct, vomerine teeth absent; tongue large, broad and lacking posterior notch; vocal sac single, gular. Forelimb long (FLL/SVL: 0.65), all fingers free of webbing, tips rounded and slightly swollen; relative finger lengths: I=II<IV<III; two prominent large palmar tubercles, not contacting each other medially, much larger than finger tips, inner palmar tubercle rounded in shape and slightly smaller than the ovate outer palmar tubercle; subarticular tubercles not distinct. Hind limbs long almost the size of SVL (HLL/SVL: 0.98), slender; heels do not contact each other when legs held at right angles to body; tibiotarsal articulation of adpressed limb reaches the angle of the jaw. Toes with thick lateral dermal fringes reaching to the toe tips; toe webbing well-developed and thick, toe webbing formula: I 0–1 II 0–2 III 0–3 IV 3–1/2 V. Tips of all toes rounded, notabl