KIZ 14102911, an adult male, collected at 21:10 on 30 June 2014 by Hong Hui from Nabang (24°46'12.03"N, 97°34’28.03"E, 354 m elevation; Fig. 2), Yingjiang County, Dehong Autonomous Prefecture, Yunnan, China.

Eight adult males: KIZ 14102901 and KIZ 14102902 collected at 20:40 on 10 July 2014 by Hong Hui from Dengga Village (23°59'21.05"N, 97°35'13.03"E, 868 m elevation; Fig. 2), Longdao Township, Ruili City, Dehong Autonomous Prefecture, Yunnan, China; KIZ 14102904–14102906 collected at 21:10 on 9 July 2014 by Hong Hui from Nanjingli Village (24°05'52.07"N, 97°50'30.07"E; 1366 m elevation; Fig. 2), Ruili City, Dehong Autonomous Prefecture, Yunnan, China, and KIZ 14102908, KIZ 14102912, and KIZ 14102913 collected at 21:10 on 30 June 2014 by Hong Hui from the type locality.

The species name is dedicated to Professor Datong Yang from Kunming Institute of Zoology, Chinese Academy of Sciences for his outstanding contribution to herptofauna research of Yunnan, China.

The new tree frog species is assigned to the genus Kurixalus based on a combination of the following characters: tips of digits enlarged to discs, bearing circum-marginal grooves; small body size (SVL range of 31.6–34.7 mm in adult males; Table 1); finger webbing poorly developed and toe webbing moderately developed; serrated dermal fringes along outer edge of forearm and tarsus; an inverted triangular-shaped dark brown mark between eyes; dorsal brown “) (” saddle-shaped marking; and coarse dorsal and lateral surfaces with small, irregular tubercles (Nguyen et al. 2014a, Nguyen et al. 2014b, Yu et al. 2017b). Our previous molecular study placed the new species in Kurixalus with other known congeners (Yu et al. 2017a).

Kurixalus yangi sp. n. can be distinguished from its congeners by a combination of the following characters: male body size larger than 30 mm; smaller ratio of head length to body size; curved canthus rostralis; weak nuptial pads; brown dorsal color; absence of large dark spots on upper-middle abdomen; presence of vomerine teeth; gold brown iris; single internal vocal sac; serrated dermal fringes along outer edge of limbs; granular throat and chest; interorbital space longer than upper eyelid; rudimentary web between fingers; and presence of supernumerary tubercles and thenar tubercle.

Figure 5. 

Dorsal (A) and ventral (B) views of the holotype of Kurixalus yangi sp. n. in preservative.

Figure 6. 

Ventral view of hand (A) and foot (B) of the holotype of Kurixalus yangi sp. n. in preservative.

Figure 7. 

lateral-dorsal (A) and ventral (B) views of the holotype of Kurixalus yangi sp. n. in life.

A small rhacophorid; HL shorter than HW; snout pointed, no dermal prominence on tip, projecting beyond margin of lower jaw in ventral view; canthus rostralis blunt and curved; lore region oblique, slightly concave; nostril oval, slightly protuberant, closer to tip of snout than eye; IND slightly narrower than IOD; pineal spot absent; pupil oval, horizontal; tympanum distinct, rounded, slightly less than half ED; supratympanic fold distinct, curving from posterior edge of eye to insertion of arm; vomerine teeth in two oblique patches, touching inner front edges of oval choanae; tongue notched posteriorly; single internal vocal sac.

Relative length of fingers is I < II < IV < III. Tips of all four fingers expanded into discs with circum-marginal and transverse ventral grooves; relative width of discs is I < II < IV < III; nuptial pad present on first finger; fingers weakly webbed at base; lateral fringes on free edges of all fingers; subarticular tubercles prominent and rounded, formula 1, 2, 2, 1; supranumerary tubercles present; two metacarpal tubercles present; series of white tubercles forming serrated fringe along outer edge of forearm.

Heels overlapping when legs at right angle to body; relative length of toes is I < II < III < V < IV; tips of toes expanded into discs with circum-marginal and transverse ventral grooves; toe discs smaller than finger discs; relative size of discs is I < II < III < V < IV; webbing moderate on all toes, webbing formula is I1.5–2II1–2III1–2IV2–1V following Myers and Duellman (1982); subarticular tubercles prominent and rounded, formula 1, 1, 2, 3, 2; supernumerary tubercles present; inner metatarsal tubercle distinct, oval; outer metatarsal tubercle absent; series of tubercles forming serrated dermal fringe along outer edge of tarsus and fifth toe.

Numerous small to large tubercles scattered on top of head, upper eyelids, dorsum, and flanks; patch of white tubercles below vent; white tubercles on tibiotarsal articulation; throat and chest finely granulated and abdomen coarsely granulated; dorsal surface of limbs smooth with tuberculs and ventral surface of thighs granulated.

Iris golden brown; dorsal surface brown, mottled with green patches and a dark brown saddle-shaped mark on dorsum behind eye; a dark brown inverted triangular-shaped mark between eyes, posterior of which extends to and touches the saddle-shaped mark; lateral head and tympanic region brown, mottled with green patches below canthus and dark brown spots on edge of upper jaw; flank light yellow, mottled with green and brown patches; limbs dorsally brown with three clear dark brown bands, mottled with green; palm of hand light red; rear, anterior, and venter of thigh red; inner side of tarsus and foot red; chest and abdomen white, fringed with yellow and mottled with small brown spots; chin clouded with dark brown and mottled with yellow patches.

In preservative, green, yellow, and red faded. Dorsal ground color brown, pattern same as in life. Flank white with brown patches; margin of lower jaw clouded with dark brown; chin, chest, and abdomen white with scattered brown spots; palm of hand dirty white; anterior, posterior, and venter of thigh dirty white, with many fine brown speckling scattered on venter of thigh; inner side of tarsus and foot dirty white.

Because the holotype and paratypes of the new species are all male, sexual dimorphism could not be determined. IND is smaller than IOD in holotype and most paratypes, but IND is larger than IOD in paratype KIZ 14102913 (Table 1). In addition, IOD is larger than UEW in holotype and most paratypes, but IOD is smaller than UEW in paratypes KIZ 14102912 and KIZ 14102913 (Table 1). Additionally, color pattern of paratype KIZ 14102912 also differs from other specimens in that its chin has much less spotting.

The new species is known from border region with northern Myanmar in western Yunnan, China (Fig. 2) and northern Myanmar according to Yu et al. (2017a). At the type locality, the new species was found calling on leaves of bushes adjacent to a road at night (Fig. 8). Specimens from the other two sites were found calling on broad leaves at the edge of an evergreen forest. Tadpoles, eggs and females were not found.

Figure 8. 

Habitat of Kurixalus yangi sp. n. at the type locality.

The new species, Kurixalus yangi sp. n., is genetically closer to K. naso than to other known members of Kurixalus according to our previous work (Yu et al. 2017a), but morphologically it can be separated from K. naso by having smaller ratios of head, snout, IND, UEW, and limbs divided by SVL (Table 2 and Fig. 3). The smaller IND and UEW ratios in the new species can be observed when comparing these distances with the IOD, which is generally larger in the new species but smaller in K. naso (Table 1).

Currently, three Kurixalus species (K. odontotarsus, K. hainanus, and K. lenquanensis Yu, Wang, Hou, Rao, & Yang, 2017) are recognized in Yunnan, China (Yu et al. 2017a, Yu et al. 2017b). The new species differs from K. odontotarsus and K. hainanus by having smaller ratio of head length to body size and no large dark spots on abdomen (versus larger ratio of head length to body size and large dark spots on entire abdomen; Figs 4, 9) and from K. lenquanensis by larger body size (SVL of 31.6–34.7 mm in adult males), more pointed snout, and presence of green coloration on dorsal surface and lateral side of head and body (versus smaller body size [SVL of adult males less than 30 mm], somewhat rounded snout, and absence of green coloration on dorsum; Fig. 9, Yu et al. 2017b).

Figure 9. 

Ventral views of A Kurixalus odontotarsus (KIZ 180019Y) B Kurixalus hainanus (KIZ 180007R), and C Kurixalus lenquanensis (KIZ 170184Y; from Yu et al. 2017b).

The new species is distinguished from Kurixalus idiootocus (Kuramoto & Wang, 1987) by larger body size, absence of a pair of symmetrical large dark patches on chest, and single internal vocal sac (versus smaller body size [SVL of adult males less than 30 mm], presence of a pair of symmetrical large dark patches on chest, and single external vocal sac; Yu et al. 2017a); from Kurixalus berylliniris Wu, Huang, Tsai, Li, Jhang, & Wu, 2016 by gold brown irises, weak nuptial pads, and coarsely granular abdomen (versus emerald to light green irises, greatly expanded nuptial pads, and smooth abdomen; Wu et al. 2016); from Kurixalus wangi Wu, Huang, Tsai, Li, Jhang, & Wu, 2016 by larger body size, weak nuptial pads, and presence of supernumerary tubercles on foot (versus smaller body size [SVL of 28.6–31.6 mm in adult males], greatly expanded nuptial pads, and absence of supernumerary tubercles on foot; Wu et al. 2016); and from Kurixalus eiffingeri (Boettger, 1895) by weak nuptial pads, oblique loreal region, and curved canthus rostralis (versus greatly expanded nuptial pads, vertical loreal region, and straight canthus rostralis; Wu et al. 2016).

In addition, Kurixalus yangi sp. n. differs from Kurixalus baliogaster (Inger, Orlv, & Darevsky, 1999) by having serrated dermal fringes on limbs, tuberculate dorsum, tubercles on eyelids, and absence of large dark spots on venter (versus no serrated dermal fringes on limbs, dorsum smooth, tubercles on eyelids absent, and large dark spots scattered on entire venter; Inger et al. 1999); from Kurixalus banaensis (Bourret, 1939) by having larger body size and vomerine teeth (versus smaller body size [SVL of 26.2–33.2 mm in adult males] and vomerine teeth absent; Nguyen et al. 2014b, Bossuyt and Dubois 2001); from Kurixalus viridescens Nguyen, Matsui, & Duc, 2014 by having brown dorsal color, dark markings on dorsum and limbs, and vomerine teeth (versus uniformly greenish dorsal color with no dark markings on dorsum and limbs, and vomerine teeth absent; Nguyen et al. 2014a); and from Kurixalus motokawai Nguyen, Matsui, & Eto, 2014 by having larger body size and vomerine teeth (versus smaller body size [SVL of 23.2–28.4 mm in adult males] and vomerine teeth absent; Nguyen et al. 2014b).

Kurixalus yangi sp. n. can be distinguished from Kurixalus ananjevae Matsui & Orlov, 2004 by having vomerine teeth, serrated dermal fringes on limbs, and finely granular throat surface (versus vomerine teeth absent, serrated dermal fringes absent, and throat surface smooth; Matsui and Orlov 2004); from Kurixalus verrucosus (Boulenger, 1893) by granular throat and chest and interorbital space longer than upper eyelid (versus throat and chest smooth and interorbital space as broad as upper eyelid; Boulenger 1893); from K. bisacculus by having single internal vocal sac (versus paired external lateral vocal sacs; Taylor 1962); and from Kurixalus appendiculatus (Günther, 1858) by having rudimentary web between fingers, supernumerary tubercles, and outer metacarpal tubercle (versus one third web between fingers, supernumerary tubercles absent, and outer metacarpal tubercle absent; Günther 1858, Brown and Alcala 1994).