Zhangixalus thaoae, Nguyen & Nguyen & Ninh & Le & Bui & Orlov & Hoang & Ziegler, 2024

Nguyen, Tao Thien, Nguyen, Huy Hoang, Ninh, Hoa Thi, Le, Linh Tu Hoang, Bui, Hai Tuan, Orlov, Nikolai, Hoang, Chung Van & Ziegler, Thomas, 2024, Zhangixalus thaoae sp. nov., a new green treefrog species from Vietnam (Anura, Rhacophoridae), ZooKeys 1197, pp. 93-113 : 93

Zhangixalus thaoae sp. nov.

Fig. 2

Material examined.

Holotype: Vietnam • ♂; Y Ty Commune, Bat Xat District, Lao Cai Province, Northwestern Vietnam; 22°37'17.6"N, 103°37'23.5"E; 1883 m a.s.l.; 01 May 2019; C. V. Hoang and A. M. Luong leg.; IEBR A 5136; GenBank: LC762092.1 . Paratypes: Vietnam • 2 ♂; same locality as for holotype; same geo-coordinates; same altitude; same collection date; same collectors; IEBR A 5137, 5138; GenBank: LC762093.1, LC762094.1 .

Diagnosis.

The new species is placed in the genus Zhangixalus based on some morphological characters: dorsum green and smooth; body size medium (SVL 30.1-32.2 in males); fingers webbed; tips of digits expanded into large disks, bearing circum-marginal grooves; absence of dermal folds along limbs; absence of supracloacal fold and tarsal projection (Fig. 2 ).

The new species is distinguished from its congeners by a combination of the following characteristics: 1) dorsal surface of head and body green without spots; 2) axilla and groin cream with a black blotch; 3) ventrum cream-colored without spots; 4) chin cream, with grey marbling; anterior part of thigh and ventral surface of tibia orange, without blotch; posterior parts of thigh orange with a large, black blotch; 5) ventral side of webbing orange, with some grey; 6) iris red-bronze, pupils black. 7) finger webbing formula I 1¼-1¼ II1-2III1-1IV, and toe webbing formula I ½-½II0-1½III¼ - 1¾IV1¾-½ V.

Description of the holotype

(male). Size medium (SVL 32.2 mm), body robust; head slightly compressed, head length nearly equal to the width (HW 12.1 mm, HL 11.7 mm), convex above; snout round, slightly protruding beyond lower jaw in lateral view, and longer than the horizontal diameter of eye (SNL 5.4 mm, ED 4.2 mm); canthus rostralis round, loreal region oblique, concave; interorbital distance wider than internarial distance and upper eyelid (IOD 4.3 mm, IND 3.1 mm, UEW 3.0 mm); distance between anterior corners of eyes about 69.30% of the distance between posterior corners of eyes; nostrils round, without lateral flap of skin, closer to tip of snout than to eye; pupil oval, horizontal; tympanum distinct, round, about half the size of eye diameter, and twice greater than distance between tympanum and eye (TYD 2.1, TYE 1.0); pineal ocellus and spinules on upper eyelid absent; vomerine teeth well developed, in two oblique ridges; choanae round; tongue deeply notched posteriorly; supratympanic fold weakly.

Forelimbs robust, upper arm short, nearly one-half of hand length (Ua 6.2 mm, Fa 14.6 mm), dermal fringe along the outer edge of forearm absent; relative finger lengths I<II<V<III; tips of fingers with enlarged discs with distinct circum-marginal grooves; disc of finger III approximately 1.5 times of the width of finger III (fd3/fw3 1.5), greater than tympanum diameter (fd3/TYD 1.27); webbing formula I 1¼-1¼ II1-2III1-1IV, subarticular tubercles distinct, blunt, round, formula 1, 1, 2, 2; nuptial pads prominent, oval, smooth.

Hindlimbs long and thin, heels overlapping when held at right angles to the body; tibia length about four times greater than tibia width (TbL 13.9 mm, TbW 3.1 mm), longer than thigh length (FeL 13.3 mm), shorter than foot length (FL 19.0 mm); relative toe lengths I<II<III<V<IV; tips of toes with enlarged discs with distinct circum-marginal grooves, discs slightly smaller than those of fingers; webbing formula I ½-½II0-1½III¼-1¾IV1¾-½ V; subarticular tubercles distinct, blunt, round, formula 1, 1, 2, 3, 2; inner metatarsal tubercle small (IML 1.6 mm); dermal ridge along the outer edge of tibia and tarsus absent; dermal projection at tibiotarsal articulation absent.

Skin texture: dorsal surface of head and body smooth; supratympanic fold weakly developed, throat and chest smooth, belly rough; ventral surface of fore- and hindlimbs smooth.

Coloration in life: iris red-bronze, pupil black; dorsal surface of head and body green without spots; dorsal surface of fore and hind limbs green, upper side of fingers II and II and toes I, II, and III yellow, all tip of fingers and toes yellow; axilla cream and groin cream with a black blotch; anterior part of thigh and ventral surface of tibia orange without spots; posterior parts of thigh orange with a large black blotch; lower jaw cream, with grey marbling, and throat region white; ventral side of webbing orange with some gray pattern, nuptial pads grey.

Coloration in preservative: As in life, but with green dorsal surface fading to dark blue; and ventral side of body, limbs, and upper side of fingers I and II, upper side of toes I, II, and III fading to light yellow.

Variation.

Ground color of dorsum light green; ventral surface cream, without spots. The size of blotches in the axilla, groin, and posterior thigh region of the paratype is smaller than in the holotype (Fig. 3 ). For measurements of the type series, see Table 3 .

Etymology.

The species is named after the first author’s wife, Nguyen Thi Thanh Thao, as a token of gratitude for her understanding and strong support of his research activity. We recommend Thao’s Tree Frog as the English common name and Ếch cây thảo as the Vietnamese common name.

Male secondary sexual characters.

Male specimens with nuptial pad present on base of the finger I and external single subgular vocal sac.

Natural history notes.

Specimens were collected between 19:00 and 24:00h on a branch about 1 m above the ground. The ground consisted of mountain soil and puddles, and there was a small stream about 2 m away (Fig. 4A ). The habitat was an undisturbed evergreen forest on a granite mountain (Fig. 4B ). Other tree frogs that were found at the site were Polypedates sp., of the P. leucomystax species complex; Zhangixalus duboisi (Ohler, Marquis, Swan & Grosjean, 2000); Hyla annectans (Jerdon, 1870); and Gracixalus gracilipes (Bourret, 1937). Females, larval stages, and eggs of the new species are unknown.

Distribution.

Zhangixalus thaoae sp. nov. is currently known only from the type locality (Fig. 5 ). The species was recorded at an elevation of approximately 1,880 m a.s.l.

Conservation status.

The new species is expected to be found in the evergreen forest of Guangxi Province, southern China, because the terrain there consists mostly of granite mountains, but in Yunnan Province, China, which contains mostly limestone terrain, the species is not expected. However, the geographic distribution of the species needs to be confirmed by further studies. Because there is a lack of information on the species’ abundance and distribution, we suggest that it be considered as Data Deficient following IUCN Red List categories ( IUCN 2023).

Comparisons.

We compare Zhangixalus thaoae sp. nov. with other species of Zhangixalus occurring in Vietnam and elsewhere.

The new species mostly resembles Z. yaoshanensis by the combination of the following characteristics: head as long as wide in Zhangixalus thaoae sp. nov. (HL/HW 0.96-1.02), posterior parts of thigh orange with a large black blotch, ventral surface of tibia orange, iris red-bronze with black pupil in Zhangixalus thaoae sp. nov. vs head wider than long (HL/HW = 0.83); posterior thigh surface and ventral surface of tibia red-orange without spot, iris pale yellowish gold with a network of fine dark gold reticulations in Z. yaoshanensis ( Chen et al. 2018).

Zhangixalus thaoae sp. nov. can be distinguished from other species in the genus Zhangixalus by its smaller size (SVL 30.1-32.2 mm) vs SVL>50 mm in the following species: 47.0-70.5 ( Wilkinson and Rao 2004; Ohler 2009; Jiang et al. 2016) in Z. burmanus ; 68-92 mm ( Fei et al. 2010) in Z. dennysi ; 53.1-67.2 mm ( Ohler et al. 2000; Orlov et al. 2001; Ziegler et al. 2014) in Z. duboisi ; 68-116 mm ( Fei et al. 2010) in Z. feae (Boulenger, 1893); 77.9-85.8 mm ( Ninh et al. 2020) in Z. franki ; 52-66 mm ( Fei et al. 2010), 52-65 mm ( Liu 1950) in Z. omeimontis ; 74.2 mm ( Luu and Calame 2014), 73.4-78.2 mm in Z. pachyproctus ( Yu et al. 2019); and 76.3-79.6 mm in Z. smaragdinus ( Yu et al. 2019).

Zhangixalus thaoae sp. nov. can be distinguished from other Zhangixalus species of a similar size in having a different coloration pattern: dorsum green without blotches or spots in the new species vs light or dark green with many white or brown spots or blotches in various sizes in Z. dugritei ( David 1872; Li et al. 2012a), Z. hongchibaensis ( Li et al. 2012a), Z. hui ( Liu 1945), and Z. wui ( Li et al. 2012a).

Zhangixalus arboreus has a green dorsum with numerous dark spots ( Okada and Kawano 1924), which is absent in Zhangixalus thaoae sp. nov.

Zhangixalus achantharrhena has a green dorsum, without spots, and a cream venter, without the brown flecks of the new species ( Harvey et al. 2002).

Zhangixalus arvalis has a white line along flanks, which is absent in Z. thaoae sp. nov. ( Lue et al. 1995).

Zhangixalus chenfui has a brown ventrum, with a dark-brown pattern, not cream-colored, without a dark-brown pattern, as in Zhangixalus thaoae sp. nov. ( Liu 1945).

Zhangixalus dorsoviridis has cream flanks with many black blotches and the anterior thigh is orange with some irregularly sized black circles ( Bourret 1937) (Figs 6C, D , 7C, D ). In Z. thaoae sp. nov., the flanks are cream with one single black spot and the posterior thigh is orange with a single large black blotch (Figs 6A, B , 7A, B ).

Zhangixalus dulitensis is pea-green dorsally with some white dots, the head and back have purplish dots, there is purplish line from eye to eye around the snout and passing through the nostrils, and there is reddish-brown patch on each eyelid ( Boulenger 1892; Haas et al. 2012). Zhangixalus thaoae sp. nov. does not have this color pattern.

Zhangixalus jarujini has a reddish-brown dorsum with irregular dark-brown markings, while Z. thaoae sp. nov. has a green dorsum without any markings.

Zhangixalus jodiae has black and orange blotches interposed on anterior, posterior part of thighs and ventral surface of tibia (Figs 6E, F , 7E, F ); Z. thaoae sp. nov. does not have this color pattern, but rather a large, black blotch on an orange background (Figs 6A, B , 7A, B ).

Zhangixalus leucofasciatus exhibits a cream axilla without dark spots, in contrast to a black blotch on the cream axilla of Z. thaoae sp. nov.; additionally, Z. leucofasciatus possesses a white stripe along the upper lip, body and limbs, a feature that is absent in Z. thaoae sp. nov. ( Liu and Hu 1962; Fei et al. 2010).

Zhangixalus pinglongensis has flanks, anterior and posterior surfaces of the thigh covered with black blotches and white spots ( Mo et al. 2016). In contrast, Z. thaoae sp. nov. lacks similar black blotches with white spots on its flanks, anterior and posterior surfaces of the thighs.

Zhangixalus minimus is characterized by a dark-brown mottling pattern on its hands and feet, which is absent in Z. thaoae sp. nov. ( Rao et al. 2006).

Zhangixalus melanoleucus is whitish cream with an irregular black pattern on the ventral surface of its thighs, shanks, dorsal surfaces of the feet and fingers I, II, and III ( Brakels et al. 2023). Meanwhile, in Z. thaoae sp. nov., the ventral surface of the thighs, shanks, dorsal surfaces of the feet and fingers I, II, and III are orange, without any irregular black pattern.

Zhangixalus moltrechti has a red-orange anterior and posterior thigh with multiple dark spots, while the thigh in Z. thaoae sp. nov. has an orange anterior with no spots and an orange posterior with a single large blotch ( Boulenger 1908; Fei et al. 2010). Furthermore, the webbings of the foot in Z. moltrechti are red-orange, with dark spots, while those in Z. thaoae sp. nov. are yellow with no spots.

Zhangixalus nigropunctatus has yellow flanks and posterior thigh with some black blotches, in contrast to Z. thaoae sp. nov., in which the flank is cream-colored and the posterior thigh is orange, both featuring a single black spot ( Liu et al. 1962; Fei et al. 2010). In Z. nigropunctatus , there is also a white stripe along the flanks and limbs, separating the dorsal and ventral sides, which is a feature that is absent in Z. thaoae sp. nov.

Zhangixalus schlegelii has flanks and groin without spots, while in Z. thaoae sp. nov. these each have a large black blotch ( Günther 1858). A white stripe along the flanks and limbs, separating the dorsal and ventral sides, is present in Z. schlegelii but absent in Z. thaoae sp. nov. Furthermore, there is a prominent supratympanic fold in Z. schlegelii , which is only weakly visible in Z. thaoae sp. nov.

Zhangixalus yinggelingensis has green dorsal head, body and limbs, adorned with a small number of very fine white spots ( Chou et al. 2007), which are absent in Z. thaoae sp. nov. In addition, the supratympanic fold in Z. yinggelingensis is prominent, whereas it is weakly visible in Z. thaoae sp. nov.

Zhangixalus yunnanensis has greyish webbings and yellowish-brown iris, which are respectively orange and red-bronze in Z. thaoae sp. nov. ( Pan et al. 2024). Furthermore, Z. yunnanensis exhibits a somewhat broader head (IND/IOD 0.96-1), which is proportionally smaller relative to the body (HL/SVL 0.31-0.33) compared to the head of Z. thaoae sp. nov. (IND/IOD 0.72-0.85, HL/SVL 0.37-0.43).

Zhangixalus zhoukaiyae has yellowish posterior thigh with irregular greyish blotching, whereas the posterior thigh of Z. thaoae sp. nov. is orange without spots. In Z. zhoukaiyae , the pupil is dark charcoal-grey and the iris is golden-yellow, while in Z. thaoae sp. nov. the pupil is black, and the iris is red-bronze ( Pan et al. 2017).

A more detailed comparison of morphological differences between Z. thaoae and other members in the Z. chenfui group can be found in Table 4 .

Figures

Figure 2. Adult male holotype (IEBR A 5136) of Zhangixalus thaoae sp. nov., in life, from Y Ty Commune, Bat Xat District, Lao Cai Province, northwestern Vietnam.

Figure 3. The variation of morphological characteristic of Zhangixalus thaoae sp. nov. IEBR A 5136 is the holotype, and the two remaining samples are paratypes.

Figure 4. Habitat of the new species in Y Ty Commune, Bat Xat District, Lao Cai Province A collection site with a small puddle B the stream near the biotope of the holotype.

Figure 5. The distribution of species of the Zhangixalus chenfui group.

Figure 6. Dorsal and ventral views of three Zhangixalus species in life (except for F, which was immediately photographed after the specimen was anesthetized) A, B Zhangixalus thaoae sp. nov. IEBR. A 5136 C, D Z. dorsoviridis VNMN 06156 E, F Z. jodiae VNMN 07122.

Figure 7. Dorsal and ventral views of three Zhangixalus species in preservative A, B Zhangixalus thaoae sp. nov IEBR. A 5136 C, D Z. dorsoviridis VNMN 06156 E, F Z. jodiae VNMN 07122.