Nidirana occidentalis, Lyu & Chen & Yang & Zeng & Wang & Zhao & Wan & Pang & Wang, 2020

Lyu, Zhi-Tong, Chen, Yang, Yang, Jian-Huan, Zeng, Zhao-Chi, Wang, Jian, Zhao, Jian, Wan, Han, Pang, Hong & Wang, Ying-Yong, 2020, A new species of Nidirana from the N. pleuraden group (Anura, Ranidae) from western Yunnan, China, Zootaxa 4861 (1), pp. 43-62 : 55-59

Nidirana occidentalis sp. nov. Lyu, Yang, and Wang

Chresonymy

Rana pleuraden— Yang and Rao 2008 (Longling, Baoshan, and Tengchong)

Pelophylax pleuraden— Fei et al. 2009 (Longling, Baoshan, and Tengchong)

Dianrana pleuraden— Fei et al. 2012 (Western Yunnan)

Babina pleuraden— Chan and Bi 2016 (Tengchong)

Nidirana pleuraden— Lyu et al. 2017 (Mt. Gaoligong)

Holotype. SYS a003776, adult male, collected by Jian Wang and Hai-Long He on 15 May 2015 from Dahaoping (24.9846°N, 98.7376°E; ca 1600 m a.s.l.), Mt. Gaoligong , Yunnan Province, PR China.

Paratypes. Males SYS a003775/ CIB 116075 , SYS a003777 and female SYS a003778, collected at the same time from the same locality as the holotype. Males SYS a007830–7831 and Females SYS a007829, 7832, collected by Jian Wang, Yu-Long Li and Yao Li on 9 June 2019 from Mengku Township (23.6586°N, 99.9847°E; ca 1980 m a.s.l.), Shuangjiang Lahu , Va , Blang and Dai Autonomous County, Yunnan Province, PR China .

Etymology. The specific name “ occidentalis ” is a Latin adjective and means “western”, referring to the distribution of the new species in western Yunnan, which takes the westernmost distribution among all congeners.

Common name. Western Yunnan Music Frog (in English) / Dian Xi Qin Wa (AEOiḪü in Chinese)

Diagnosis. Nidirana occidentalis sp. nov. is placed in the genus Nidirana based on the morphological characteristics of the absence of the thumb-like structure on finger I, presence of well-developed dorsolateral folds, and the presence of suprabrachial glands in breeding males ( Lyu et al. 2017), and is further assigned to the N. pleuraden group by the absence of lateroventral groove on all digits ( Dubois 1992; Lyu et al. 2019).

Nidirana occidentalis sp. nov. is distinguished from all known Nidirana congeners by the following combination of the morphological characteristics: (1) body medium-size and elongated, SVL 49.1 ± 3.3 (44.5–53.0, N = 5) mm in adult males and 58.8 ± 2.9 (55.6–61.3, N = 3) mm in adult females; (2) head relatively short, HDW/HWL 0.84 ± 0.05 in males and 0.86 ± 0.04 in females; (3) tympanum relatively small, TD/ED 0.81 ± 0.02 in males and 0.77 ± 0.02 in females (4) lateroventral grooves absent on every digit; (5) absence of supernumerary tubercles on hand; (6) tibio-tarsal articulation reaching at the eye; (7) heels just meeting; (8) posterior of dorsal skin rough with tubercles and spinules; (9) a pair of subgular vocal sacs in males; (10) one single nuptial pad present on the first finger in breeding males, nuptial spinules invisible; (11) suprabrachial gland large and smooth; (12) calling: 3–5 identical regular notes.

Description of holotype: SYS a003776 ( Fig. 6 ), adult male. Body elongated, SVL 47.5 mm; head relatively short, flat above; snout rounded in dorsal and lateral views, slightly protruding beyond lower jaw, longer than horizontal diameter of eye (SNT/ED 1.33); canthus rostralis distinct, loreal region concave; nostril round, closer to the snout than to the eye; a longitudinal swollen mandibular ridge extending from below nostril through lower edges, eye and tympanum to above insertion of arm; supratympanic fold absent; interorbital space flat, narrower than internasal distance (IND/IOD 1.29); pupil elliptical, horizontal; tympanum distinct, round, relatively small, and close to eye; pineal ocellus invisible; vomerine ridge present, bearing small teeth; tongue large, cordiform, notched behind. Presence of a pair of subgular vocal sacs, a pair of slit-like openings at posterior of jaw.

Forelimbs moderately robust, lower arm 17% of SVL and hand 28% of SVL; fingers thin, relative finger lengths II <I <IV <III; tip of each finger not dilated and without lateroventral grooves; fingers free of webbing; presence of weak lateral fringes on inner and outer sides of fingers II, III and IV; subarticular tubercles prominent and rounded; absence of supernumerary tubercles; three elliptic, large, prominent and very distinct palmar tubercles. A single nuptial pad on the dorsal surface of first finger, nuptial spinules invisible.

Hindlimbs relatively robust, tibia 51% of SVL and foot 82% of SVL; heels just meeting when hindlimbs flexed at right angles to axis of body; tibio-tarsal articulation reaching at the eye when hindlimb is stretched along the side of the body; toes relatively long and thin, relative lengths I <II <V <III <IV; tip of each toe not dilated and with- out lateroventral grooves; webbing moderate, webbing formula: I 2–2½ II 2–3 III 2½–3⅔ IV 4–2½ V; presence of lateral fringes on inner and outer sides of each toes, forming distinct dermal flap on the lateral edges of toes I and V; subarticular tubercles rounded, prominent; inner metatarsal tubercle elliptic; outer metatarsal tubercle absent, small and rounded; tarsal folds and tarsal tubercle absent.

Dorsal skin of head and anterior body smooth, posterior dorsum of body rough with dense tubercles and horny spinules; developed dorsolateral fold from posterior margin of upper eyelid to above groin but intermittent posteriorly; flank smooth; a large and smooth suprabrachial gland behind base of forelimb, not prominent; dorsal surfaces of thigh and tibia with several longitudinal ridges and bearing spinules. Ventral surface of head, body, and limbs smooth; large flattened tubercles densely arranged on the rear of thigh and around vent.

Coloration of holotype. Photos of the holotype in life were not taken and the coloration data is lacking. In preservative, dorsal surface of head and body dark brown; a longitudinal light mid-dorsal stripe extending from snout to vent; dorsolateral fold bicolor, upper part light brown and lower part black; flank light brown with irregular black spots; suprabrachial gland creamy. Dorsal forelimbs light brown; a longitudinal black stripe on the anterior surface of the forelimb; irregular black marks on dorsal surface of the forelimb; dorsal hindlimbs reddish brown with black crossbars on the thigh, tibia and tarsus; nuptial pad grey. Loreal and temporal regions dark brown; tympanum light brown. Lips and throat white; ventral surface of body and limbs creamy white; rear thigh tinged with pink; ventral hand and foot pale.

Variations. Measurements of type series are given in Table 3 and photos of paratypes are shown in Fig. 7 . All type series specimens were similar in morphology. Females are significantly larger than males, with the sexual size dimorphism of 83.5%. SYS a007830–7832 have several tubercles on the upper flank, not bearing spinules. Suprabrachial glands prominent in SYS a007830 (vs. not prominent in holotype SYS a003776 and paratype SYS a007831).

The coloration of Nidirana occidentalis sp. nov. is variable, from yellowish brown, reddish brown to dark brown on dorsum; pineal ocellus invisible; a light mid-dorsal stripe edged with broad darker stripes extending from forehead to vent; black spots scatter on posterior dorsum. Dorsolateral fold bicolor, light color upper and darker lower part; flank varies from light brown to dark brown, with small black spots or large black patches. One black stripe in front of the base of forelimb; irregular dark marks on lateral forelimb; three to four dark brown or black crossbars on thigh, tibia and tarsus. Temporal region lighter color with a yellowish arc patch in SYS a007830, 7831; maxillary gland and shoulder gland white; upper ⅓ iris brownish white and lower ⅔ iris reddish brown. Ventral surface of body and limbs creamy white; several black spots on the edge of ventral belly and limbs in SYS a007832. Surface of throat darker; ventral hand and foot purplish brown.

Distribution and ecology. Currently, Nidirana occidentalis sp. nov. is recognized from multiple localities in western Yunnan, all of which are situated to the west of the Red River ( Fig. 1 ). This frog inhabits natural or artificial ponds surrounded by moist subtropical secondary evergreen broadleaved forests, and is common in its habitat, sympatric with Tylototriton shanjing Nussbaum, Brodie, and Yang, 1995 , Nanorana yunnanensis (Anderson, 1879) , and Zhangixalus puerensis (He, 1999) . The adult males were heard calling in the water surface from May to July.

Figures

FIGURE 1. Recognized localities of Nidirana occidentalis sp. nov. and N. pleuraden in Yunnan Province, PR China. 1: Mt. Gaoligong (type locality of N. occidentalis sp. nov.) and Wuhe Township, Tengchong City; 2: Shuangjiang Lahu, Va, Blang and Dai Autonomous County; 3: Longyang District, Baoshan City; 4: Mingguang Township, Tengchong City; 5: Longling County; 6: Wumulong Yi Ethnic Township, Yongde County; 7: Mahuangjing Village, Yongde County; 8: Linxiang District, Lincang City; 9: Xishan District, Kunming City (type locality of N. pleuraden); 10: Lake Yangzonghai, Kunming City; 11: Luxi County; 12: Huaning County; 13: Wenshan City; 14: Dayao County; 15: Huaping County.

FIGURE 6. Adult male holotype SYS a003776 of Nidirana occidentalis sp. nov. in preservative. A: dorsal view; B: ventral view; C: lateral view; D: right hand. E: left foot.

FIGURE 7. Coloration in life and variations of Nidirana occidentalis sp. nov. A: male paratype SYS a007830; B: male paratype SYS a007831; C: female paratype SYS a007832; 1: dorsolateral view; 2: ventral view.