Gracixalus liusanjieae sp. nov.

Figs 5, 6, 7, 8

Type material.

Holotype. • GXNU YU 000978, an adult male collected on 4 April 2025 by Guohua Yu, Yuanqiang Pan, and Xiangjian Wu from Maoershan National Natural Reserve, Guilin, Guangxi, China (25.911°N, 109.466°E, 1573 m elevation).

Paratypes. • Two adult males (GXNU YU 000795, GXNU YU 000796) collected on 26 April 2024 by Guohua Yu, Yuanqiang Pan, and Xiangjian Wu, • an adult male (GXNU YU 000962) collected on 13 August 2024 by Tongxiang Zou, and • two adult females (GXNU YU 000979 and GXNU YU 000980) collected on 26 April 2025 by Guohua Yu, Yuanqiang Pan, and Xiangjian Wu. All paratypes were collected from the type locality.

Etymology.

The specific epithet is named for Sanjie Liu, referring to a famous woman in Chinese ancient legend who came from Guangxi and who was known for her exceptional singing talent. The specific name means that the new species is distributed in Guangxi and its advertisement calls are melodic. We suggested “ Maoershan small tree frog ” for the common English name and “ 刘三姐纤树蛙 (Liú Sān Jiě Xiān Shù Wā) ” for the common Chinese name.

Diagnosis.

The new species is assigned to genus Gracixalus based upon the following set of morphological characters: tips of digits enlarged to discs bearing circum-marginal grooves, vomerine teeth absent, inner (first and second) and outer (third and fourth) fingers not opposable, and an inversed Y-shaped dark brown marking on the dorsum (Fei 1999; Yu et al. 2019; Tran et al. 2023).

The new species can be distinguished from its congeners by a combination of the following morphological characters: (1) SVL 27.5–33.2 mm in males and 38.1‒39.7 mm in females; (2) dorsal surface beige to brown; (3) dorsal surface rough with a few flatten tubercles on dorsum; (4) internal vocal sac in males, vocal sac opening slitted; (5) throat relatively smooth with barely visible tubercles; (6) finger webbing rudimentary; (7) linea masculina absent; (8) snout rounded; (9) tibiotarsal articulation reaching center of eye; (10) tibiotarsal projection absent; (11) nuptial pads present on fingers I and II; (12) heels slightly overlapping when legs at right angle to body; (13) ventral surface translucent, creamy white with dark blotches; (14) belly granular.

Description of holotype.

Small size (SVL 33.2 mm); head wider (HW 12.1 mm) than long (HL 11.4 mm); snout rounded, slightly projecting beyond margin of lower jaw in ventral view, rounded in profile; canthus rostralis rounded; nostril oval, protuberant, closer to tip of snout than eye; loreal region oblique, slightly concave; interorbital distance (IOD 3.7 mm) nearly equal to internarial distance (IND 3.6 mm) and upper eyelid width (UEW 3.3 mm); eye large, horizontal diameter (ED 3.8 mm) slightly shorter than snout length (SL 4.2 mm); pupil oval, horizontal; tympanum distinct (TD 1.6 mm), slightly 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; single internal vocal sac, a pair of vocal sac slits on floor of mouth at both corners.

Forelimbs relatively strong; forearm and hand length (FHL 17.4 mm) longer than 50 % of SVL; relative finger lengths I <II <IV <III; finger webbing rudimentary; tips of all fingers expanded into discs with circum-marginal grooves; subarticular tubercles prominent and rounded, formula 1, 1, 2, 2, the proximal one smaller than the distal one on fingers III and IV; two metacarpal tubercles, the outer divided into two; nuptial pads white, present on the base of the first and the second fingers.

Heels meeting when legs at right angle to body; the relative lengths of the toes I <II <III <V <IV; tibiotarsal articulation reaching the middle of the eye when hindlimb adpressed to body; tip of toes expanded into discs with circum-marginal grooves; toe discs slightly smaller than finger discs; half web between toes, webbing formula I 2–2 ⅓ II 1 ½ – 3 III 1 ½ – 2 ⅔ IV 2 ⅓ – 1 ⅔ V; subarticular tubercles prominent, round, formula 1, 1, 2, 3, 2; a few supernumerary tubercles present; inner metatarsal tubercle oval, outer metatarsal tubercle absent.

Dorsal surface rough, sparsely scattered with a few small flatten tubercles on the upper eyelids, head, dorsum, and limbs; white tubercles scattered on temporal region, edge of upper and lower jaw, and dorsal surface of limbs; flank rough, scattered with white tubercles; throat relatively smooth with barely visible tubercles; chest and belly granular, and ventral surface of thighs rough scattered with white tubercles.

Coloration of holotype. In life, dorsal surface beige; a dark brown inverted Y-shaped marking on dorsal surface covering interorbital region, bifurcating into two branches on shoulder and extending posteriorly; dorsal surface of limbs beige with dark brown stripes; anterior and posterior parts of thigh light yellow; ventral surface of thigh light yellow mottled with light purple; discs of fingers and toes light yellow; flanks beige; throat and chest creamy white with dark speckles; iris bronze (Fig. 5).

In preservative, color faded but pattern same as in life; dorsal surface gray-brown with a dark brown inverted Y-shaped marking; dark brown stripes on limbs; ventral surface dirty white with dark speckles (Fig. 6).

Sexual dimorphism. Females are larger than males in body size. Males have white nuptial pads on the base of fingers I & II (Figs 5, 7 C) and internal single subgular vocal sac.

Morphological variation. The dorsal surface of paratypes GXNU YU 000795 and GXNU YU 000979 is dark brown, whereas the dorsal surface of other types is beige or brown (Figs 7, 8). Paratypes GXNU YU 000962 and GXNU YU 000980 have less dark blotches on ventral surface (Fig. 8). In addition, the inverted Y-shaped marking on the dorsum in paratype GXNU YU 000980 is discontinuous (Fig. 8).

Advertisement call. The advertisement calls of the new species consist of two notes (Fig. 9 A). The call duration of the new species is 0.66‒ 0.80s (0.74 ± 0.04; Table 7) and the peak frequency is 2.58 kHz. The frequency range is 2.2‒2.9 kHz and the interval between calls ranges from 5.6s to 18.2s (8.9 ± 2.9).

Distribution and ecology. Currently, the new species is known only from the type locality. The new species inhabits bamboo forest (Fig. 10) and enters breeding season in early April. Eggs with gel nests were found on the broken branches placed on the bottles that were used as artificial breeding trap for surveillance of tree frogs (Fig. 10), and calls were heard during the surveys. Zhangixalus minimus (Rao, Wilkinson & Liu, 2006) was also found at the type locality.

Measurements of holotype

(in mm). SVL 33.2, HL 11.4, HW 12.1, SL 4.2, IND 3.6, IND 3.7, UEW 3.3, ED 3.8, TD 1.6, FHL 17.4, TL 15.8, TFL 22.8, FL 15.5.

Comparisons.

Phylogenetically, the new species is closer to G. jinxiuensis, G. huaping, and G. weii than to other species. Gracixalus liusanjieae sp. nov. is distinguishable from G. jinxiuensis, with which the new species has previously been confused, by nuptial pads distinct, white, present on the base of fingers I and II (vs. nuptial pads not distinct, light yellow, present on the base of finger I), longer forearm and hand (FHL / SVL 0.509 ± 0.0136 vs. 0.4779 ± 0.0107), longer foot (FL / SVL 0.452 ± 0.0113 vs. 0.417 ± 0.0135), and longer duration of advertisement calls (0.74 ± 0.04 vs. 0.51 ± 0.03; Table 7); from G. weii by nuptial pads present on fingers I and II (vs. on finger I), larger body size in females (SVL 38.1‒39.7 mm vs. 35.2‒36.0 mm), longer head (HL / SVL 0.342 ± 0.011 vs. 0.324 ± 0.009), shorter snout (SL / SVL 0.131 ± 0.0037 vs. 0.153 ± 0.0034), narrower internarial distance (IND / SVL 0.107 ± 0.004 vs. 0.128 ± 0.005), shorter tibia (TL / SVL 0.476 ± 0.007 vs. 0.4945 ± 0.011), shorter tarsus and foot (TFL / SVL 0.681 ± 0.123 vs. 0.709 ± 0.015), and longer foot (FL / SVL 0.452 ± 0.011 vs. 0.426 ± 0.018); and from G. huaping by bigger body size (SVL 27.5–33.2 mm in males and 38.1‒39.7 mm in females vs. SVL 26.6‒28.8 mm in males and 29.8‒32.8 mm in females), linea masculina absent (vs. present), vocal sac opening slitted (vs. oval and rim of the opening dark brown), nuptial pads present on fingers I and II (vs. on finger I), and advertisement calls composed of two notes (vs. one note; Fig. 9).

The new species can be distinguished from G. ananjevae (Matsui & Orlov, 2004) by nuptial pads present on fingers I and II (vs. on finger I), finger webbing rudimentary (vs. finger webbing formula I 2‒2 II 2 ‒ basalIII 3 ‒ 2.75 IV) and the presence of white granules around anus and on limbs (vs. absent); from G. carinensis (Boulenger, 1893) by smaller body size (SVL 27.5–31.5 mm in males and 38.1‒39.7 mm in females vs. 30.2–38.1 mm in males and 40.3‒41.8 mm in females), less developed toe webbing (Fig. 11), and tubercles on dorsum present (vs. absent); from G. gracilipes by bigger body size (SVL 27.5–31.5 mm in males and 38.1‒39.7 mm in females vs. 20–24 mm in males and ca. 30 mm in females), snout rounded (vs. triangularly pointed), and dorsal surface beige to brown (vs. greenish); from G. guangdongensis by nuptial pads present on fingers I and II (vs. on finger I), bigger body size in females (38.1‒39.7 mm vs. 34.9‒35.4 mm), and longer duration of advertisement calls (0.74 ± 0.04 vs. 0.56 ± 0.07); from G. jinggangensis by heels overlapping (vs. just meeting) and calls composed of two notes with no harmonics (vs. three or four notes with multiple harmonics); from G. lumarius by smaller body size (SVL 27.5–31.5 mm in males vs. 38.9–41.6 mm in males), dorsal surface rough sparsely scattered with flatten tubercles (vs. dorsal surface of head and back covered in dense and distinctive white conical tubercles), nuptial pads present on fingers I and II (vs. on finger I), and supratympanic fold distinct (vs. indistinct); and from G. medogensis (Ye & Hu, 1984) by dark brown mark beginning between eyes bifurcated into two wide branches after the back of shoulders (vs. bifurcated into two relatively narrow branches before the back of shoulders), dorsal color beige to brown (vs. grass green), finger webbing rudimentary (vs. absent), linea masculine absent (vs. present), and nuptial pads present on fingers I and II (vs. on finger I).

Gracixalus liusanjieae sp. nov. differs from G. nonggangensis by dorsal surface beige to brown with dark-brown mark (vs. yellowish-olive with dark-green mark), nuptial pads on fingers I and II (vs. absent), iris bronze (vs. olive), and advertisement calls composed of two notes (vs. 40‒72 notes); from G. patkaiensis Boruah, Deepak, Patel, Jithin, Yomcha & Das, 2023 by bigger body size (SVL 27.5–31.5 mm in males vs. 23.6‒26.5 mm in males), dorsal surface beige to brown (vs. green with brown spots), vocal sac internal (vs. external), and nuptial pads on fingers I and II (vs. on finger I); from G. quangi Rowley, Dau, Nguyen, Cao & Nguyen, 2011 by larger body size (SVL 27.5–31.5 mm in males vs. 21.4‒24.5 mm in males), dorsal surface beige to brown (vs. olive-green), vocal sac internal (vs. external), snout rounded (vs. triangularly pointed), nuptial pads present on fingers I and II (vs. on finger I), and tibiotarsal projection absent (vs. present); and from G. quyeti (Nguyen, Hendrix, Böhme, Vu & Ziegler, 2008) by dorsal surface beige to brown (vs. brownish to moss-green), head wider than long (vs. head longer than wide), tibiotarsal articulation reaching center of eye (vs. reaching to snout), supratympanic fold distinct (vs. indistinct), and forelimb, dorsal parts of thighs, tibia, and foot brown with dark brown bands (vs. moss-green with dark brown bands).

The new species differs from G. sapaensis Matsui, Ohler, Eto & Nguyen, 2017 by nuptial pads present on fingers I and II (vs. on finger I) and ventral surface of throat and chest creamy white (vs. light yellow); from G. seesom Matsui, Khonsue, Panha & Eto, 2015 by bigger body size (SVL 27.5–31.5 mm in males vs. 21.6–23.0 mm in males), snout rounded (vs. triangularly pointed), dorsal surface rough scattered with tubercles (vs. smooth), dorsal surface beige to brown with dark brown inverted Y-shaped marking (vs. tan), and nuptial pads present on fingers I and II (vs. absent); from G. supercornutus (Orlov, Ho & Nguyen, 2004) by bigger body size (SVL 27.5–31.5 mm in males vs. 22.0– 24.1 mm), dorsal surface beige to brown (vs. dorsum green with brown spots), snout rounded (vs. pointed), white patch on temporal region absent (vs. present), dorsal surface nearly smooth (vs. considerable bigger horn-like projections in supraorbital area, around cloaca, and on dorsum, forelimbs and hindlimbs), and tibiotarsal projection absent (vs. present); and from G. tianlinensis by vocal sac internal (vs. external), ventral of thigh rough with tubercles (vs. ventral surface of limbs smooth), finger webbing rudimentary (vs. absent), and calls lacking harmonic (vs. present).

Gracixalus liusanjieae sp. nov. differs from G. trieng Rowley, Le, Hoang, Cao & Dau, 2020 by smaller body size (SVL in males 27.5–31.5 mm vs. 37.2–41.4 mm), presence of white tubercles on temporal region, edge of upper and lower jaw, flank, and dorsal surface of limbs (vs. absent), and throat and chest white with dark specks (vs. yellow or yellowish brown with pinkish mottling); from G. truongi Tran, Pham, Le, Nguyen, Ziegler & Pham, 2023 by smaller body size (SVL 27.5–31.5 mm in males vs. 32.2–33.1 mm in males), dorsal surface beige to brown (vs. moss green with grey), and nuptial pads present on fingers I and II (vs. on finger I); from G. yunnanensis Yu, Li, Wang, Rao, Wu & Yang, 2019 by vocal sac internal (vs. external), linea masculine absent (vs. present), and nuptial pads present on fingers I and II (vs. on finger I); and from G. ziegleri Le, Do, Tran, Nguyen, Orlov, Ninh & Nguyen, 2021 by nuptial pads present on fingers I and II (vs. on finger I), skin of throat relatively smooth (vs. granular), and tibiotarsal articulation reaching center of eye (vs. reaching tip of snout).