Rhacophorus dulongensis Chen, Lee & Yuan, 2024

Lee, Ping-Shin, Liu, Ben, Ouyang, Meng, Ai, Ren-Da, Liu, Xiao-Long, He, Yan-Hong, Huang, Ping-Qian, Li, Ying-Chun, Naveen, R. S., Yuan, Zhi-Yong & Chen, Jin-Min, 2024, Hidden in the bamboo: A new parachuting frog (Rhacophoridae, Rhacophorus) from the borderlands of western China, with comments on the taxonomy of R. rhodopus, Zoosystematics and Evolution 100 (3), pp. 851-862 : 851-862

Rhacophorus dulongensis Chen, Lee & Yuan sp. nov.

Figs 3 , 4

Type materials.

Holotype. ANU 010645 , adult male, collected from Dulongjiang Village , Gongshan County, Nujiang Prefecture, Yunnan Province, China (27.7838 ° N, 98.3248 ° E, 1620 m a. s. l.; Fig. 1 ) on 15 February 2022, by Renda Ai . Paratypes. ANU 010646 , adult female, collected at the same time as the holotype from the type locality by Renda Ai .

Etymology.

The specific epithet “ dulongensis ” is given as a noun in apposition and refers to the name of the Dulongjiang Village, where the new species occurs. We suggest the English common name “ Dulongjiang tree frog ” and the Chinese common name “ 独龙江树蛙 ” (dú lóng jiāng shù wā).

Diagnosis.

Rhacophorus dulongensis sp. nov. can be distinguished from its congeners by the following combination of morphological characters: (1) body size small ( SVL 31.7 mm in male; 35.3 mm in female); (2) head length longer than head width; (3) tibia length shorter than half of snout-vent length; (4) third finger disk smaller in diameter than tympanum; (5) snout pointed without a distinct bulge; (6) the tibiotarsal articulation reaches the eye when hindlimb is stretched along the side of the body; (7) dorsal surface of body uniformly green, and dorsal surface of limbs brown with irregular green patches; (8) belly mostly yellowish, rough, and granular (9) large black warts present on ventral surface of thigh near vent; (10) webs between toes red and webbing formula on toes: I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V; (11) black spots at axillary region absent; (12) vomerine teeth weakly developed; (13) iris darkgoldenrod; (14) maxillary teeth distinct; (15) tongue notably notched posteriorly.

Description of holotype.

Adult male, body size small ( SVL 31.7 mm); head length (HL 9.8 mm) longer than head width ( HW 8.7 mm); snout pointed, protruding from the margin of the lower jaw, longer (SL 4.6 mm) than diameter of eye ( ED 3.5 mm); canthus rostralis distinct; loreal region oblique; nostril small, closer to tip of snout than to eye; interorbital space ( IOS 2.8 mm) longer than internasal space ( INS 2.5 mm) and width of upper eyelid ( UEW 2.1 mm); pupil horizontal and iris darkgoldenrod; pineal ocellus absent; tympanum rounded and distinct, diameter of tympanum ( TD 1.7 mm) shorter than half of eye diameter ( ED 3.5 mm), internasal space ( INS 2.5 mm) and interorbital space ( IOS 2.8 mm); supratympanic fold distinct; maxillary teeth distinct; vomerine teeth weak; internal single subgular vocal sac; vocal sac openings small, slit-like; tongue heart-shaped, attached anteriorly, with distinct notch at posterior end; choanae oval (Table 3 ).

Forelimbs thin, slender and not very long; length of lower arm and hand ( LAHL 13.4 mm) shorter than half snout-vent length ( SVL 31.7 mm); relative length of fingers: III> IV> II> I; tips of fingers expanded into discs; finger webbing formula: I 2 + - 2 1 / 3 II 1 + - 2 2 / 3 III 2 1 / 3 -1 2 / 3 IV; subarticular tubercles distinct, blunt and round; third finger disk shorter than diameter of tympanum ( TD 1.7 mm); supernumerary tubercles below the base of finger present; nuptial pads absent; inner metacarpal tubercle distinct, large and oval (Fig. 3 ; Table 3 ).

Hindlimbs slender, relatively long, tibia length ( TIL 14.6 mm) shorter than half of snout-vent length ( SVL 31.7 mm) and thigh length ( THL 15.2 mm); tibiotarsal articulation reaches the eye when hindlimb is stretched along the side of the body; heels overlapping when held at right angles to the body; relative length of toes: IV> V > III> II> I; tips of toes expanded into discs; subarticular tubercles on all toes round, distinct, and protuberant; entire web between toes; toes webbing formula: I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V; inner metatarsal tubercle small; outer metatarsal tubercle absent (Fig. 3 ; Table 3 ).

The dorsal surface of body smooth and uniformly green; dorsal surface of limbs brown with irregular green patches; the skin of throat, chest, and ventral surface of tibia, foot, and tarsus smooth; black dusting present on the margin of the throat; the belly mostly yellowish and rough; large black warts present on ventral surface of thigh near vent; dermal fringe along the outer sides of limbs indistinct; webs between toes red; black spots at axillary region absent.

Color of holotype in preservative.

Dorsal color darkened; ventral surface faded to creamy white; brown dusting present on ventral surfaces of throat. The patterns of dark spots and markings all over the body are the same as in life. Large black warts on the ventral surface of the thigh near the vent are more distinct (Figs 3 , 4 ).

Male secondary sexual characteristics.

Nuptial pad and lineae masculinae were not observed.

Morphological variation.

The paratype matches the overall characters of the holotype (Table 3 ; Fig. 4 ). Female larger than male ( SVL 35.3 mm in one female and 31.7 mm in one male). The male has small slit-like vocal sac openings. Dusting pattern on the belly, chest, throat, and ventral surfaces of limbs varies individually. Female has more distinct brown dusting on the venter than male (Figs 3 , 4 ).

Distribution and ecology.

Rhacophorus dulongensis sp. nov. is presently known only from its type locality, near Dulongjiang Village, Gongshan County, Nujiang Prefecture, Yunnan Province, China. Both individuals of the new species were found inside bamboo internodes along rocky streams in well-preserved montane evergreen broadleaf forest (Fig. 5 ). Vocal recordings and tadpoles of this new species were not collected.

Comparisons.

Rhacophorus dulongensis sp. nov. is distinguishable from all other species of Rhacophorus by a combination of features of body size, head length, tibia length, snout and tongue shape, toe webbing formula and coloration, ventral skin texture and coloration, dorsal pattern and coloration, body macroglands, iris coloration, and pattern of markings on flanks ( Tao et al. 2014; Fei et al. 2009; Li et al. 2012; Che et al. 2020; Li et al. 2022; Naveen et al. 2023).

In particular, R. dulongensis sp. nov. can be easily distinguished from its four morphologically and phylogenetically close congeners ( R. tuberculatus , R. orlovi , R. spelaeus , and R. turpes ; Figs 2 , 6 ; Table 3 ). Specifically, it differs from R. tuberculatus by having green dorsum coloration in life (vs. uniform brown dorsum coloration), different webbing formula on toes (I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V vs. I 1 1 / 2 -2 1 / 2 II 1 1 / 3 -2 1 / 2 III 1 + - 2 1 / 3 IV 2 -- 1 - V), as well as the absence of a prominent calcar at tibio-tarsal articulation (vs. presence) and the absence of dark stripes on the hindlimb (vs. presence).

R. dulongensis sp. nov. differs from R. orlovi by having smaller head (HL / SVL = 0.30–0.31 vs. HL / SVL = 0.38–0.41), different webbing formula on toes (I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V vs. I 1 0 -2 0 II 1 0 -2 0 III 1 0 -2 0 IV 2 0 -1 0 V), green dorsal coloration in life (vs. reddish brown), hindlimb without transverse stripes (vs. limbs with transverse stripes), as well as the presence of large black warts on the ventral surface of the thigh (vs. absence) and the absence of spotting on flanks (vs. presence).

R. dulongensis sp. nov. differs from R. spelaeus by having smaller body size in males ( SVL 31.7 vs. 38.9–43.1 mm), different webbing formula on toes (I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V vs. I 0-1 II 0 - 1 / 2 III 1 - 0 V 1 / 2 - 1 / 2 V), green dorsal coloration in life (vs. grey-brown coloration in life), ventral surface of belly yellowish (vs. light gray), as well as the presence of vomerine teeth (vs. absence).

Specifically, R. dulongensis sp. nov. differs from R. turpes by having hindlimbs without dark stripes (vs. hindlimbs with dark stripes), by different webbing formula on toes (I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V vs. I 1 1 / 3 -1 1 / 2 II 1 1 / 2 -1 2 / 3 III 1 0 -1 1 / 2 IV 2 0 -1 0 V), vomerine teeth weak and small (vs. vomerine teeth distinct and large), dermal projection on the heel poorly developed (vs. well-developed), having a relatively longer foot length ( FL / SVL ratio 0.36–0.41 in R. dulongensis sp. nov. vs. 0.29 in R. turpes ), numerous and large black warts on ventral surface of thigh (vs. few and small in R. turpes ), as well as the absence of small black spots in male (vs. presence in R. turpes ) (Fig. 6 ).

In addition, R. dulongensis sp. nov. further differs from R. rhodopus , the notoriously “ widespread ” species of Rhacophorus in China and Indochina, by head length longer than head width (vs. head length almost equal to head width), third finger disk shorter than diameter of tympanum (vs. third finger disk longer than diameter of tympanum), tibia length shorter than half of snout-vent length (vs. tibia length about half of snout-vent length), as well as the absence of the black spots at axillary region (vs. presence), the absence of dermal calcars on vent (vs. present), and the absence of transverse stripes on hindlimb (vs. presence).

Among the species that are geographically close to R. dulongensis sp. nov., it distinctly differs from R. bipunctatus by having distinct tympanum (vs. indistinct), head length longer than head width (vs. head length almost equal to head width), as well as the absence of dermal calcars on heels (vs. presence), and the absence of black spots at axillary region (vs. presence). R. dulongensis sp. nov. differs from R. translineatus by having smaller body size ( SVL 31.7 mm in male, 35.3 mm in female vs. 49.4–54.1 mm in males, 61.5–65.2 mm in females), different webbing formula on toes (I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V vs. I 0-0 II 0 - 0 III 0 - 0 - IV 0 - 0 V), as well as the absence of transverse dark brown lines on the back (vs. presence), and the absence of an appendage on the tip of snout (vs. presence). R. dulongensis sp. nov. differs from R. subansiriensis by having smaller body size in male ( SVL 31.7 mm vs. 37.0–39.0 mm), head length longer than head width (vs. head length shorter than head width), as well as the absence of dark cross bands on limbs (vs. presence), and the absence of spots on flanks (vs. presence).

For the remaining congeners, R. dulongensis sp. nov. differs from R. kio by having smaller body size ( SVL 31.7 mm in male, 35.3 mm in female vs. 58.0– 79.1 mm in male, 82.6–88.9 mm in female), different webbing on toes (entirely webbed vs. fully webbed), red web (vs. web with black spot and orange yellow distal zone), as well as the absence of pointed dermal flap on heels (vs. presence), and the absence of black marking on flanks (vs. presence). R. dulongensis sp. nov. differs from R. laoshan by having fifth finger longer than third finger (vs. equal), different webbing formula on toes (I 1 0 -1 2 / 3 II 1 -- 2 1 / 2 III 1 + - 2 1 / 3 IV 2 1 / 3 -1 1 / 3 V vs. I 1-2 1 / 2 II 1-2 1 / 2 III 1-2 1 / 2 IV 2-1 V), limbs without broad transverse stripes (vs. limbs with broad transverse stripes), and uniform green dorsum coloration in life (vs. chocolate brown dorsum coloration with wide dark cross-shaped mark). R. dulongensis sp. nov. differs from R. napoensis by having smaller body size in male ( SVL 31.7 mm vs. 38.6–43.6 mm), head width shorter than head length (vs. head width longer than head length), the tibiotarsal articulation reaches the eye (vs. the tibiotarsal articulation reaches the snout), as well as the absence of a distinct bulge on the tip of snout (vs. presence), the absence of black spots at axillary region (vs. presence), and the absence of horizontal banding on dorsum and dorsal surface of limbs (vs. presence).

Lastly, R. dulongensis sp. nov. can be distinguished by its smaller body size in male ( SVL 31.7 mm vs. 53.16 mm in R. barisani ; 40.5–46.7 mm in R. bengkuluensis ; 50.9 mm in R. borneensis ; 60.0 mm in R. helenae ; 49.9 mm in R. larissae ; 64.7 mm in R. norhayatiae ; 66.8 mm in R. pseudomalabaricus ; over 58.0 mm in R. reinwardtii ; 49.5–68.2 mm in R. malabaricus ; 46.3 mm in R. pardalis ; 45.9–46.4 mm in R. exechopygus ); green dorsum coloration in life (vs. brown in R. barisani , R. margaritifer and R. vanbanicus ; brown with darker cross bands in R. bengkuluensis and R. catamitus ; yellowish grey with brown blotches in R. hoabinhensis ; reddish brown with irregular dark brown blotches in R. indonesiensis ; X-shaped blotch on the anterior part of the back in R. monticola ; cream-colored in R. marmoridorsum ; dark grey or brownish-grey in R. calcadensis ; yellowish grey in R. hoabinhensis ); head longer than head width (vs. head wider than long in R. calcaneus , R. baluensis , R. trangdinhensis and R. viridimaculatus ); third finger disk shorter than diameter of tympanum (vs. third finger disk longer than diameter of tympanum in R. calcaneus , R. annamensis , R. hoanglienensis , R. exechopygus , R. robertingeri and R. baluensis ); red webs between toes (vs. black webs in R. borneensis ; proximally black and distally greenish webs in R. helenae ; yellow webs in R. edentulus ); tibiotarsal articulation reaches the eye (vs. tibiotarsal articulation reaches the tip of the snout in R. nigropalmatus ; tibiotarsal articulation reaches beyond the tip of snout in R. georgii ); absence of narrow dark cross-streaks on the limbs (vs. presence in R. bifasciatus ); absence of a white streak on each side of body (vs. presence in R. lateralis ); absence of a large triangular calcar heel (vs. presence in R. robertingeri ).

Figures

Figure 1. Map showing the collection site and type locality of Rhacophorus dulongensis sp. nov. (A; red circle) and R. rhodopus (B; green square).

Figure 2. Phylogram of Rhacophorus inferred from a 16 S rRNA mtDNA gene fragment. “ * ” denotes high support by bootstrap support values (BS> 75 %) and Bayesian posterior probabilities (BPP > 0.95); nodes without any numbers or symbols represent low support values (BS < 75 % and BPP < 0.95). Outgroup taxa are not shown. The inserted photo (acknowledgment to Renda Ai) shows Rhacophorus dulongensis sp. nov. Scale bars represent the number of substitutions per site. The new samples for the present study are indicated by the red font. R. rhodopus is framed by the purple shade.

Figure 3. Holotype of Rhacophorus dulongensis sp. nov. (ANU 010645) in life. A. Dorsal view; B. Ventral view; C. Dorso-lateral view; D. Ventral surface of the thigh and the cloacal region; E. Plantar view of the left foot; F. Thenar view of the right hand. The blue arrow in D points to large black warts. Photos by Renda Ai.

Figure 4. Type series of Rhacophorus dulongensis sp. nov. in preservation. A. ANU 010645; B. ANU 010645; A 1. Dorsal view; A 2. Ventral view; B 1. Dorsal view; B 2. Ventral view. The blue arrows in A 2 and B 2 point to large black warts. Photos by Renda Ai.

Figure 5. Habitat of Rhacophorus dulongensis sp. nov. at the type locality in Dulongjiang Village, Yunnan Province, China. B, C. show the native bamboo species, Cephalostachyum virulentum, where the new species inhabits. Photos by Ying-Chun Li.

Figure 6. Type series of Rhacophorus turpes. A. The illustration of R. turpes in the original literature (Smith 1940); B, C. The syntype of R. turpes (BMNH 1940.6. 1.30) in the dorsal and ventral views, respectively (Photos by R. S. Naveen).