Rhacophorus minimus, Rao, Ding-Qi, Wilkinson, Jeffery A. & Liu, Hui-Ning, 2006

Rao, Ding-Qi, Wilkinson, Jeffery A. & Liu, Hui-Ning, 2006, A new species of Rhacophorus (Anura: Rhacophoridae) from Guangxi Province, China, Zootaxa 1258, pp. 17-31 : 18-24

Rhacophorus minimus sp. nov.

Guangxi diminutive treefrog

Holotype. KIZ 2003 GXJX 0021 ( Fig. 1 ), an adult female, collected from Shiliugongli (24 08' 32.2" N, 110 14'26.4" E), 900 m, a small village at the 16 km marker from the town of Jinxiu on the road from Jinxiu to Mengshan, Dayao Mountain, Jinxiu County, Laibin Prefecture, Guangxi Province, China, collected on 10 April 2003 by D.­Q. Rao.

Paratypes. KIZ 2003 GXJX 001, 2003 GXJX 003­06, 2003 GXJX 008­20, 2003 GXJX 0022­23, CAS 232043­44 nineteen males and three females collected at the same locality and date as the holotype; KIZ 2003 GXJX 0024­32 nine males collected from Xiang­Lu­Chong, 1200­1600 m, Dayao Mountain, Jinxiu County, Laibin Prefecture, Guangxi Province, China, collected on 10–15 April 2003 by D.­Q. Rao.

Diagnosis. Rhacophorus minimus can be distinguished from all other species of Rhacophorus and Polypedates by the following combination of characters: very small body size (mean SVL male 28.1 mm, mean SVL female 37.0 mm); reduced webbing on the hand; disc of 3rd finger smaller than diameter of tympanum; smooth dorsum; green dorsal color; and white stripe from tip of snout along the upper lip and shoulder to insertion of hind limbs.

Description of holotype. An adult female with slender body and head 35% of SVL and slightly wider than long. Snout rounded in dorsal view, gently slopes from eye to nostrils, then more abruptly to mandible in lateral view ( Fig. 2 a); nostril equidistant between eye and tip of snout, slightly protuberant, directed laterally; canthus rostralis distinct, angular, and concave in dorsal view. Snout between eyes and nostrils and between nostrils and tip of snout slightly concave. Loreal region slightly oblique, concave to nostril; eye large, width 84% snout length, directed anterolaterally with horizontal pupil; interorbital region 140% that of upper eyelid. Tympanum distinct and circular, 57% of diameter of eye, with raised annulus; supratympanic fold curves ventrally from posterior edge of eye to insertion of arm, does not conceal dorsal aspect of tympanum; raised linear fold with weak glandular tubercles from corner of jaw below tympanum to beyond posteroventral end of supratympanic fold. Vomerine processes, with 5 teeth each, slanting posteriorly from their lateral contact with anteromedial edge of choanae, medial ends slightly beyond posterior edge of choanae, separated by a distance three times their width; choanae small, ovoid to anteromedial and posterolateral points, and wholly visible at edge of lingual shelves of maxillae when viewed ventrally. Tongue shallowly bifurcates posteriorly, posterior 2/3 free.

Dorsal body surface smooth; ventral abdominal surface areolate, pectoral and gular regions much less areolate; skin of posterior and ventral surface of thigh beneath anal opening with a scattering of round tubercles; slight elevation of skin above vent.

Arms short, forearm slender; hand relatively large, 81% as long as foot; when adpressed, relative length of fingers is 3> 4> 2> 1. Tips of fingers rounded. Digital pads on hands and feet well developed and oval, with circummarginal grooves; pad on third finger smaller than tympanum. Distal phalanges Y­shaped (as seen from dorsal aspect of digital tips). Hands webbed only at base, webbing formula for digits is I2.5–2.5II2– 3 III2.5–2.25IV following Myers and Duellman (1982). Subarticular tubercles between penultimate and adjoining proximal phalange round and well developed; proximal subarticular tubercles on finger 4 smallest. Fingers 1–4 each with an additional supernumery tubercle proximal to the proximal subarticular tubercle. Inner metacarpal tubercle low, oval, and indistinct, outer tubercle low, indistinct, and bifid distally ( Fig. 2 b).

Hind limbs relatively short; heels do not meet when legs at right angle to body; and when adpressed to body, tibiotarsal articulation reaches to posterior half of eye. Webbing formula is I1.5– 2II 1.5–2.5 III2 –2.5IV2.5–1.5V. When adpressed, relative length of toes is 4> 5 = 3> 2> 1. A single subarticular tubercle on toes 1 and 2, two subarticular tubercles on toes 3, 4, and 5. Proximal tubercles smaller than distal tubercles. Supernumerary tubercles and an outer metatarsal tubercle absent. Inner metatarsal tubercle oval and raised distally ( Fig. 2 c).

Coloration in preservative. Dorsal color of body light blue, extending laterally and ventrally 1/2 of flanks, from elbow to halfway up middorsal aspect of hindarm, and along dorsal aspect of forearm to wrist, from vent to knee along middorsal aspect of thigh, and entire dorsal aspect of tibia. Dark blotches near nostrils, tympanum, and sparsely scattered on dorsum. Lateral border of dorsal blue with white rough­edged line from tip of snout to insertion of hind limb. Posterior margin of tarsus and supracloacal fringe with white line ventrally bordered by black line. Dorsally, hand from wrist, and foot from tarsus, olive to light cream with darker brown mottling. Tips of fingers light cream with scattered dark mottling. Venter, flanks, ventral aspect of arms and legs cream with scattered mottling, more so on thigh. Ventral aspect of hands and feet with darker pigmentation especially along lateral half.

Color in life. Dorsal color bright green, pattern same as when preserved ( Fig. 3 ). Hands and feet light brown with dark brown mottling. Tips of fingers and toes yellowish green. Iris yellow peripherally to brown medially, more yellow on dorsal half.

Variation. Males smaller than females, with head as long as broad; and snout slanting less abruptly from nostrils to an obtuse point projecting beyond mandible ( Fig. 3 ); light brown coloration at nostrils more evident in some specimens than others; some specimens with small scattered asperities on head or upper eyelid; some specimens with more pronounced dark brown mottling on back of thigh while others with little to no mottling; white lateral line pronounced in some specimens while fading posteriorly in others.

Tadpole. Description based on individual at Gosner (1960) stage 35 (KIZ 2003GXJX0033). Total length 25.5 mm, body length 9.2 mm, body height 3.8 mm, maximum tail height 3.9 mm, tail muscular height 2.3 mm, body width 5.9 mm, internarial distance 1.7 mm, eye to tip of snout 3.1 mm, eye diameter 0.9 mm, interorbital distance 2.2 mm. Body oval with weak lateral constriction in dorsal view ( Fig. 4 a), dorso­ventrally depressed in lateral view ( Fig. 4 b); snout round in dorsal and lateral views; oral disc ventral, 41% body width, emarginate, marginal papillae in two rows on anterior and posterior labia but not between labia, large dorsal gap and narrow ventral gap present, submarginal papillae not present, medium (darkly keratinized for approximately half of sheath), serrated jaw sheath, with short lateral process of upper jaw, labial tooth row formula 5(2–5)/3(1) ( Fig. 4 c); eyes dorsal, nares midway between eyes and tip of snout directed antero­laterally; spiracle single, sinistral, at midbody, directed postero­dorsally, vent dextral; tail musculature gradually tapering posteriorly to tail tip; tail height 24% tail length; body height 97% of tail height; tail highest midway, gradually declining to rounded tail tip; dorsal and ventral fins slightly arched approximately equal in height.

Tadpole color in life. Black from early stages to metamorphosis, then becoming green after four limbs are developed and tail completely absorbed.

Tadpole color in preservative: Dorsum of body brownish gray due to densely scattered brown chromatophores; venter transparent with much fewer scattered brown chromatophores, more so laterally; muscular tail light cream with brown reticulation extending onto transparent dorsal fin; ventral fin transparent without reticulation. Etymology. The name minimus , from the Latin meaning for smallest, referring to its small body size.

Comparisons. Because R. minimus possesses expanded discs on the fingers and toes, an intercalary element between the penultimate and terminal phalanges, a narrow bony metasternum, a flange on the distal end of the third metacarpal, Y­shaped terminal phalanges, and webbing between the fingers and toes, it is related to species in the genera Polypedates and Rhacophorus ( Wilkinson and Drewes 2000) . Rhacophorus minimus can be distinguished from most members of these relatively large genera (approximately 28 species for Polypedates and 56 species for Rhacophorus [ Frost 2004]) by a small body size and a green dorsal color. In addition, it can be distinguished from similarly small body size species by the following: from Rhacophorus angulirostris Ahl , R. bipunctatus Ahl , R. dulitensis Boulenger , R. edentulus Müller , R. monticola Boulenger , and R. turpes Smith by reduced webbing (at least outer fingers fully webbed in aforementioned species); from Rhacophorus appendiculatus Günther , R. everetti Boulenger , and R. kajau Dring , by a smooth dorsal surface (highly tuberculate in aforementioned species); from Polypedates dugritei David and P. zhaojuensis Wu and Zheng by a lack of brown patterning on the green dorsal background; from P. dorsoviridis (Bourett) and P. nigropunctatus (Liu, Hu, and Yang) by a lack of dark spotting on the flanks; and from P. c h e n f u i (Liu), P. hungfuensis (Liu and Hu) , R. schlegelii (Günther) , R. taipeianus Liang and Wang , and P. yaoshanensis by a smaller, more slender body (male SVL at less than 33 mm, female SVL at less than 41 mm).

Rhacophorus minimus further differs from the similar appearing Chinese species ( P. chenfui , P. hungfuensis , and P. yaoshanensis ) by a lack of tiny tubercles scattered on the dorsum, presence of white stripe from tip of upper lip to insertion of hind limb (present from midway along lower lip or corner of mouth to insertion of hind limb in P. chenfui and absent in P. hungfuensis and P. yaoshanensis ), and webbing between outer fingers less than one third length of fingers (over one third in P. chenfui , approximately one third in P. hungfuensis , and approximately one half in P. yaoshanensis ).

In addition, Rhacophorus minimus differs from P. chenfui and P. hungfuensis by the disc of 3rd finger being smaller than tympanum (larger than tympanum in P. chenfui and equal to tympanum in P. hungfuensis ). Rhacophorus minimus further differs from P. hungfuensis by a lack of white pin­size dots on green dorsum, scattered mottling on the flanks and thighs, brown hands, and yellowish green discs (flanks, thighs, and discs a light yellow, dorsal aspect of hands green in P. hungfuensis ); and R. minimus also differs from P. yaoshanensis by a blunter snout (sharp in P. yaoshanensis ) and absence of red on preaxial and postaxial region of thighs.

Distribution and natural history. At present Rhacophorus minimus is known only from the localities listed for the holotype and paratypes ( Fig. 5 ).

The males were mostly found calling in the grass within or beside shallow ponds, males and amplexing pairs were also found in wooden trays set out by local people to ambush­hunt birds. White foam egg­nests were found on the sides of the wooden trays. Males were calling during the day and night, but more so at night. In some areas, the habitat was dry, and what little water that was present was in the wooden trays, so the frogs were limited to these sites for breeding. Some frogs were calling from perches within broad­leaf trees. The surrounding habitat was undisturbed monsoonal evergreen forest with mostly broad­leaf trees.

Figures

FIGURE 1. Dorsal (A) and ventral (B) views of the holotype of Rhacophorus minimus (KIZ 2003 GXJX 0021). Scale bar = 10 mm.

FIGURE 2. Lateral view of the head (A), palmar view of the left hand (B), and plantar view of the left foot (C) of the holotype of Rhacophorus minimus (KIZ 2003 GXJX 0021). Scale bar = 5 mm.

FIGURE 3. Photograph in life of an amplectant pair of Rhacophorus minimus (male CAS 232043, female KIZ 2003 GXJX 0010).

FIGURE 4. Dorsal (A), lateral (B), and mouth (C) views of the tadpole of Rhacophorus minimus (KIZ 2003 GXJX 033). Scale bar = 10 mm.

FIGURE 5. Type locality of Rhacophorus minimus sp. nov. (indicated by star) in Guangxi Province, China.