Holotype.KIZ 20160222, an adult male, collected at 21:05 on 1 June 2017 by Hong Hui from Xuelin Township, Lancang County, Yunnan Province, China (23°0'39.4"N, 99°31'54"E, 1864 m elevation).

Paratypes. Seven adult males: KIZ 20160223 collected at 21:05 on 1 June 2017 by Hong Hui from the type locality; KIZ 20160216 collected at 21:00 on 7 June 2014 by Hong Hui from Bada Township, Menghai County, Yunnan Province, China (21°50'8.9"N, 100°6'57.8"E, 1870 m elevation); KIZ 20160226 collected at 21:50 on 27 May 2017 by Hong Hui from Fudong Township, Lancang County, Yunnan Province, China (23°7'13.6"N, 99°58'33.9"E, 2166 m elevation); KIZ 20160228–20160230 collected at 21:40–22:15 on 10 June 2017 by Hong Hui from Fazhanhe Township, Lancang County, Yunnan Province, China (22°24'3.4"N, 100°12'4.2"E, 1822 m elevation); and GXNU YU000060 collected at 21:00 on 7 June 2018 by Jian Wang from Mt. Huanglian, Lvchun County, Yunnan Province, China (22°53'N, 102°18'E, 1918 m elevation).

The specific epithet yunnanensis refers to the distribution of this species in China, Yunnan Province.

The new species is assigned to genus Gracixalus based upon molecular data and the following morphological characters: the presence of intercalary cartilage between terminal and penultimate phalanges of digits, tips of digits enlarged to discs bearing circummarginal grooves, vomerine teeth absent, inner (first and second) and outer (third and fourth) fingers non-opposable, and an inversed Y-shaped dark brown marking on dorsum (Fei 1999, Rowley et al. 2011, Chen et al. 2018). The new species is distinguished from its congeners by a combination of 1) SVL 26.0–34.2 mm in males; 2) dorsal surface yellow brown or red brown; 3) distinctive conical tubercles on dorsum; 4) males with an external subgular vocal sac; 5) throat granular; 6) finger webbing rudimentary; 7) linea masculina, a band of connective tissue between the rectus abdominus muscle and oblique abdominus muscle, present in males; 8) tibiotarsal articulation reaching eye; 9) snout rounded; 10) white patch absent on temporal region; 11) tibiotarsal projection absent; 12) supratympanic fold distinct; 13) ventral surface orangish, nearly immaculate, and semi-transparent; 14) nuptial pads present on finger I; 15) heels overlapping when legs at right angle to body; 16) iris bronze; and 17) body sides nearly smooth with no black blotch.

Adult male (SVL 29.7 mm); head wider (HW 10.9 mm) than long (HL 9.5 mm); snout rounded, slightly projecting beyond margin of lower jaw in ventral view, rounded in profile; canthus rostralis rounded; loreal region oblique, slightly concave; nostril oval, protuberant, closer to tip of snout than eye; IND (2.9 mm) slightly narrower than IOD (3.0 mm) and wider than UEW (2.5 mm); eye large, horizontal diameter (ED 4.2 mm) equal to snout length (SL 4.2 mm); pupil oval, horizontal; pineal ocellus absent; tympanum distinct, diameter (TD 1.5 mm) smaller than half of ED; supratympanic fold distinct, extending from posterior corner of eye to above insertion of arm; vomerine teeth absent; tongue notched posteriorly; a pair of vocal sac slits on floor of mouth at both corners; an external subgular vocal sac.

Forelimb relatively robust; length of forearm and hand (FHL 14.1 mm) 47% of SVL; relative length of fingers I < II < IV < III; tips of all fingers expanded into discs with circummarginal grooves; disc of third finger large, slightly wider than tympanum; nuptial pads present on base of finger I; webbing between fingers rudimentary; subarticular tubercles prominent, rounded, single, formula 1, 1, 2, 2; supernumerary tubercles present; an inner metacarpal tubercle, oval; one outer metacarpal tubercle, rounded.

Heels overlapping when legs at right angle to body; tibiotarsal articulation reaching to middle of eye when hindlimb adpressed to body; relative length of toes I < II < III < V < IV; tips of toes expanded into discs with circummarginal grooves; discs of toes smaller than those of fingers; toes webbed, webbing formula I1.5–2II1.5–2.7III.5–3IV2.5–1.5V following Savage (1975); subarticular tubercles distinct and rounded, formula 1, 1, 2, 3, 2; supernumerary tubercles present; inner metatarsal tubercle oval; outer metatarsal tubercle absent.

Dorsal surface scattered with many small conical tubercles on head, upper eyelids, and dorsum; flanks of body and dorsal surface of limbs smooth, few small conical tubercles on hindlimbs and forearms; throat, chest, belly, and venter of thigh granulated; few small conical tubercles scattered on venter of thigh, tibia, and forearm.

In life, iris bronze; dorsal surface yellow brown with a dark brownish Y-shaped marking across back, covering interorbital region and posterior eyelids, bifurcating into two branches on the shoulder, and reaching the posterior of the back; limbs dorsally brown with dark brown bars; sides of head faint brown; flanks yellow brown, mottled with faint pink on lower part; minute dark spots densely scattered on lower part of flanks, temporal region, and upper jaw; skin of ventral surface semi-transparent, orangish with yellow spots; nuptial pads and discs faint yellow; linea masculina visible, white (Fig. 4b).

In preservative, color faded, pattern same as in life. Dorsal surface grayish brown, with a darker brown Y-shaped marking; dorsal side of limbs barred with dark brown; ventral surface of throat, chest, belly, forelimbs, and hindlimbs faded to whitish.

Measurements are shown in Table 3. Because the holotype and paratypes of the new species are all male, sexual dimorphism could not be determined. IOD is slightly wider than IND in holotype and most paratypes with the exception of KIZ 20160228, and TL is longer than FL in holotype and most paratypes with exceptions of KIZ 20160226 and KIZ 20160229.

Color of dorsal and ventral surfaces varied among individuals. Dorsal ground color of the holotype and four paratypes (KIZ 20160216, KIZ 20160223, KIZ 20160228, and KIZ 20160230) is yellow brown, and dorsal ground color of remaining paratypes (KIZ 20160226, KIZ 20160229, and GXNU YU000060) is red brown. Ventral surface of all specimens is nearly immaculate with the exception of paratype GXNU YU000060, which has dark marbling on throat, chest, and belly (Fig. 6). Conical tubercles on dorsum of specimens with red brown ground color are more distinct visually (Fig. 6).

In China, the new species is known from Yunnan (Lancang County, Menghai County, Lvchun County, and Jinping County). In addition, the new species also occurs in Laos (Houapan) and Vietnam (Lao Cai and Nghe An) because our molecular analyses revealed that samples from Houapan (KUHE 32453), Lao Cai (VNMN 4355, 4357, 4371), and Nghe An (AMS R173454) that were sequenced by previous studies also belong to the new species (Figs 2, 3). In Yunnan, specimens were found sitting on leaves of herbaceous plants (e.g., Amomumtsaoko and Eupatoriumadenophorum). No eggs and tadpoles were found.

A summary of morphological comparisons presents in Table 4. The new species can be distinguished from G.ananjevae by having distinctive conical tubercles on dorsum (versus absent), sides of body smooth (versus coarsely granular), skin of throat granular (versus plain), and snout rounded (versus slightly pointed); from G.carinensis by having smaller body size in males (SVL 26.0–34.2 mm versus 30.2–38.1 mm), having distinctive conical tubercles on dorsum (versus absent), having an external vocal sac in males (versus an internal vocal sac), ventral surface orangish (versus white), and less developed toe webbing (Fig. 7); from G.gracilipes by having bigger body size in males (SVL 26.0–34.2 mm versus 20–24 mm), distinctive conical tubercles present on dorsum (versus absent), dorsal surface yellow brown or red brown (versus greenish), males with an external vocal sac (versus internal), throat granular (versus smooth), finger webbing rudimentary (versus absent), tibiotarsal articulation reaching to eye (versus reaching to between eye and nostril), snout rounded (versus triangular pointed), white patch absent on temporal region (versus present), tibiotarsal projection absent (versus present), and iris bronze (versus brown); and from G.guangdongensis by having distinctive conical tubercles on dorsum (versus absent), dorsal surface yellow brown or red brown (versus brown), flanks nearly smooth with no black blotches on ventrolateral region (versus flanks rough, scattered with tubercles and black blotches on ventrolateral region), snout rounded (versus triangularly pointed), ventral surface orangish (versus throat and chest creamy white and belly light brown), and iris bronze (versus iris brown).

Gracixalusyunnanensis sp. n. differs from G.jinggangensis by having distinctive conical tubercles on dorsum (versus absent), flanks nearly smooth (versus rough with tubercles), snout rounded (versus triangularly pointed), ventral surface orangish and immaculate (versus throat and chest dirty white with dark specks, belly white anteriorly with dark marking and posteriorly yellowish), nuptial pads present only on finger I (versus nuptial pads present on fingers I and II), heels overlapping when hindlimbs held at right angles to the body (versus just meeting), and iris bronze (versus iris golden); from G.jinxiuensis by larger body size in males (SVL 26.0–34.2 mm versus 23.5–26.3 mm), males with an external vocal sac (versus vocal sac internal), flanks nearly smooth (versus rough with tubercles), linea masculina present (versus absent), ventral surface orangish and immaculate (versus ventral surface gray-brown with dark marbling), and sole of feet and palms smooth (versus rough with dense large tubercles); and from G.lumarius by smaller body size in males (SVL 26.0–34.2 mm versus 38.9–41.6 mm), dorsal surface yellow brown or red brown (versus yellow), and venter orangish and semi-transparent (versus venter opaque pink), supratympanic fold distinct (versus indistinct), and iris bronze (versus dark gold).

Gracixalusyunnanensis sp. n. can be distinguished from G.medogensis by having distinctive conical tubercles on dorsum (versus absent), dorsal surface yellow brown or red brown (versus grass green), males with an external vocal sac (versus an internal vocal sac), finger webbing rudimentary (versus absent), and venter orangish (versus pale green); from G.nonggangensis by having conical tubercles on dorsum (versus absent), dorsum yellow brown or red brown with a dark brown marking (versus yellowish-olive with a dark-green marking), males with an external vocal sac (versus internal), flanks smooth (versus rough with tubercles), finger webbing rudimentary (versus absent), linea masculina present in males (versus absent), tibiotarsal articulation reaching to eye (versus reaching to tip of snout), ventral surface immaculate (versus throat, chest, and belly white with dark marbling), nuptial pads present on finger I (versus absent), and iris bronze (versus olive); from G.quangi by having bigger body size in males (SVL 26.0–34.2 mm versus < 25 mm), dorsal surface yellow brown or red brown (versus olive-green), black spots absent on flanks and ventral surface of thighs (versus present), throat granular (versus smooth), finger webbing rudimentary (versus absent), snout rounded (versus triangular pointed), white patch absent on temporal region (versus present), tibiotarsal projection absent (versus present), and ventral surface orangish (versus opaque white with translucent pale green margins); and from G.quyeti by dorsal surface yellow brown or red brown (versus brownish to moss-green), flanks nearly smooth (versus rough with sharp tubercles), throat granular (versus smooth), tibiotarsal articulation reaching to eye (versus reaching to snout), supratympanic fold distinct (versus indistinct), and throat and chest immaculate (versus throat, margin of throat, and chest yellow-white with brown marbling).

Gracixalusyunnanensis sp. n. differs from G.sapaensis by having distinctive conical tubercles on dorsum (versus absent) and sides of body nearly smooth (versus coarsely scattered with large round tubercles); from G.seesom by bigger body size in males (SVL 26.0–34.2 mm versus 21.6–23.0 mm), conical tubercles present on dorsum (versus absent), dorsal surface yellow brown or red brown (versus tan), flanks nearly smooth with no white blotches (versus flanks with large tubercles and white blotches), throat granular (versus smooth), snout rounded (versus triangular pointed), nuptial pads present on finger I (versus absent), and iris bronze (versus golden); and from G.supercornutus by bigger body size in males (SVL 26.0–34.2 mm versus 22.0–24.1 mm), conical tubercles on dorsum small (versus considerable bigger horn-like projections in supraorbital area, around cloaca, and on dorsal surface, forelimbs and hindlimbs), dorsal surface yellow brown or red brown (versus greenish), snout rounded (versus triangular pointed), white patch absent on temporal region (versus present), and tibiotarsal projection absent (versus present).

The new species can be distinguished from G.tianlinensis by smaller body size in males (SVL 26.0–34.2 mm versus 30.3–35.9 mm), distinctive conical tubercles present on dorsum (versus absent), dorsal surface yellow brown or red brown (versus brown to beige), finger webbing rudimentary (versus absent), ventral surface orangish, immaculate, and semi-transparent (versus throat and chest gray with dark specks and belly creamy white, opaque), and nuptial pads present on finger I (versus on fingers I and II); and from G.waza by having distinctive conical tubercles on dorsum (versus absent), dorsal surface yellow brown or red brown (versus greyish-green to moss-green), throat granular (versus smooth), finger webbing rudimentary (versus absent), and ventral surface immaculate (versus throat and chest with dark marbling).