Meristogenys stenocephalus, Shimada & Matsui & Yambun & Sudin, 2011

Shimada, Tomohiko, Matsui, Masafumi, Yambun, Paul & Sudin, Ahmad, 2011, A taxonomic study of Whitehead’s torrent frog, Meristogenys whiteheadi, with descriptions of two new species (Amphibia: Ranidae), Zoological Journal of the Linnean Society 161 (1), pp. 157-183 : 173-175

MERISTOGENYS STENOCEPHALUS SP. NOV.

Meristogenys whiteheadi: Stuart (2008: 51) . Diagnosis: A large species of the M. jerboa species group ( Matsui, 1986), with male SVL 48.0– 60.4 mm and female SVL 76.5–86.6 mm; rear of thigh dark brown, dusted with small irregular light spots; fourth toe fully webbed to disk; TL relative to SVL usually greater than 0.70; head narrow, HW and HL relative to SVL usually less than 0.35 and 0.41, respectively.

Etymology: Specific name from stenos (Greek), meaning narrow, and cephalus (Greek) meaning heads, referring to the relatively small and narrow head of this species.

Holotype: BORNEENSIS 12810; an adult male from Ulu Senagang , Crocker Range National Park, Sabah, Malaysia (5°20′40′N, 116°01′45″E, 550 m a.s.l.), collected by Masafumi Matsui, Kanto Nishikawa, Tomohiko Shimada, and Ahmad Sudin on 18 August 2003.

Paratypes: BORNEENSIS 12809; a female from the type locality.

Referred specimens: Twenty-nine males, three females, and two juveniles from Kimanis, Melalap, Kepipiyo , and Mendolong , all from Sabah (see Appendix 2) .

Description of holotype (measurements in mm): Body moderately slender, SVL 60.4; head triangular, longer (24.3) than wide (19.5); snout obtusely pointed, projecting slightly beyond lower jaw; eyes elevated; canthi sharp, slightly concave; lores slightly oblique, concave; nostrils lateral, just below canthal edge, distinctly closer to tip of snout (4.3) than to eye (5.3); IND (6.1) wider than IOD (5.1); latter narrower than UEW (6.6); SL 10.1; eye–mouth distance 1.8; nostril– mouth distance 3.3; pineal spot visible, slightly behind the line connecting anterior corners of orbits; tympanum distinct, TDv (5.2) and TDh (5.0) less than two-thirds of EL (9.1); T–EL (2.1) two-fifths of TDv and TDh; nostril–tympanum distance 15.6; snout– tympanum distance 20.4; vomerine teeth obvious, in small oblique groups separated by the half of one group, groups on line connecting rear rims of choanae; tongue deeply notched, without papilla; paired subgular vocal sacs forming gular pouches at corners of throat; vocal opening just inside commissures of jaws.

Fingers slender, first (8.2) and second subequal, much shorter than third (12.4); tips expanded into disks having circummarginal grooves; the disk of first finger smallest of all; disks of second, third (2.4), and fourth fingers subequal in diameter, half of TDv and TDh; no fringes of skin along fingers; no supernumerary metacarpal tubercles; distinct nuptial pads covering dorsal and medial surfaces of the first finger from its base to subarticular tubercle.

Hindlimb (127.3) approximately 3.2 times length of FLL (39.4); LAL 31.2; HAL 18.1; tibia long (43.3); heels overlapping when limbs are held at right angles to body; THIGH (36.8) and FL (33.7) much shorter than TL. Toe disks similar to those of fingers in shape and size (disk diameter of fourth toe 2.4); all toes fully webbed to disks; excision of web between fourth and fifth toes reaching to middle of proximal and middle subarticular tubercle of fourth toe; a narrow fringe of skin along medial edge of first toe; inner metatarsal tubercle elliptical, shorter (2.9) than distance between it and subarticular tubercle of first toe; a small round, raised outer metatarsal tubercle.

Skin of dorsum finely granular on head and trunk; a weak fold from above eye to axilla; a low dorsolateral glandular fold; side of trunk coarsely granular; thighs strongly rugose above; throat smooth; chest and abdomen weakly rugose.

Colour in life (see Figs 2E and 7C ): Dorsum light to dark brown, without markings; supratympanic fold with interrupted dark streak; upper lip whitish yellow without markings; lower lip whitish with weak dark spots; iris bicoloured, yellowish green above and below, with a small portion of reddish orange in between; centre of tympanum dark without light spot; a blackish brown band beginning behind eye, bordering rear of the tympanum, diverging above the tympanum, and nearly reaching the inguinal area; dorsal and ventral boundaries obscure; limbs marked dorsally with alternating light- and dark-brown crossbars; rear of thigh light brown with scattered light spots; throat, chest, and abdomen whitish; ventral surfaces of legs whitish, with dense dots of melanophores.

Colour in alcohol: Colour pattern has not been changed after preservation in ethanol for several years, except for iris colour, which soon disappeared after fixation in formalin solution.

Larvae ( Fig. 7D ): We examined 26 specimens of stage 26–40 of Gosner (1960) from Sg. Tinuman and Ulu Senagang. Head–body length ranges from 12.6– 14.9 mm in stages 26–29, 16.4–18.9 mm in stages 30– 33, 19.0– 22.1 mm in stages 34–37, and 21.2–24.4 mm in stages 38–40 ( Table 7).

Head–body oval, broadly rounded at snout, flat below, eyes dorsolateral, not visible from below, pointing outward; nostril open, rim not raised, closer to eye than to tip of snout.

Oral disk ventral; upper lip separated from snout by a groove; upper lip with short marginal papillae in lateral third, inframarginal papillae near corner; lower lip with uninterrupted row of short marginal papillae; LTRF 7(4–7)/7(1) to 7(4–7)/8(1); upper jaw sheaths M-shaped, lower jaw sheaths V-shaped; upper jaw sheaths divided; lower jaw sheaths undivided; jaw sheaths heavy, completely black except for outer margins covered by thin film; upper sheath film thicker than the lower sheath film; outer surface of lower jaw sheaths with several weak ribs; margin finely serrate, 8–19 and 7–13 serrae on half of upper and lower jaw sheaths, respectively; a large suctorial abdominal disk following oral disk; peripheral part of disk darkened and keratinized.

Spiracle sinistral; tube moderately long, length subequal to length of eyeball, pointing upward and backward, free of body wall for half its length; anal tube median, free of tail; tail heavily muscled, dorsal margin strongly convex, deepest before middle, tapering to slightly pointed tip; caudal muscle deeper than fins in basal half; dorsal fin origin behind body, fin deeper than ventral fin, except in final fourth; ventral fin origin at end of proximal third of tail; head–body with four pairs of glandular clusters; a postorbital cluster about an eye length behind eye, with between one and six glands; a infraorbital at the base of snout, with up to three glands; a prespiracular cluster just anterior to the spiracle, with up to nine glands; a midlateral at the posterior end of the body, with up to six glands; no dorsal fin glands; up to six ventral fin glands; whole head–body scattered dorsally with minute protuberances in older larvae; the area occupied by spinules, and their density larger in older larvae than in younger larvae; lateral line pores indistinct.

Head–body light brown dorsally and laterally, sometimes posterior half of lateral surface dark brown; caudal muscle light brown; fins translucent, with scattered pigmentations; pigmentations densely covering both fins in older larvae.

Range: Besides the type locality (Ulu Senagang; 550 m a.s.l.), this species has been collected from Kimanis (820 m a.s.l.), Kepipiyo (380 m a.s.l.), Melalap (700 m a.s.l.), Mendolong (590 m a.s.l.), and Sg. Tinuman (750 m a.s.l.). The larvae collected from the Kaingeran River (a part of larva D in Inger, 1966 and Inger & Gritis, 1983) also seem to be this species (see comparison with known larvae). This species is most likely distributed in hilly areas of the Crocker Range, Western Sabah, Malaysia.

Natural history: Larvae collected in August 2003 and November 2006 at Ulu Senagang and in March 2007 at Sg. Tinuman, showed a wide range of developmental stages. Thus, there seems to be no particular reproductive season. Larvae were collected from rivers of 10–15 m in width in both localities.

Variation: Males and females differ greatly in SVL (male, 48.0– 60.4 mm; female, 76.5–86.6 mm) and relative ratio of TDh and TDv to SVL (male, 8.0– 10.1% in TDh, 6.6–9.6% in TDv; female, 6.3–6.9% in TDh, 5.5–5.8% in TDv; see Table 4). The iris of specimens from Ulu Senagang was bicoloured, as shown above, whereas those from Kimanis were bicoloured, with yellow above and reddish orange below. We have no information for iris coloration of specimens from other localities. Dorsal coloration changes from dark brown to light brown depending on the surrounding environment.

Figures

Figure 2. Profiles of M. cf. whiteheadi. Patterns of upper lip were separated into five types: (A) pattern 1-a, several large black spots similar to those of lower lip; (B) pattern 1-b, irregular black blotches smaller than lower lip spots; (C) pattern 2, uniformly black; (D) pattern 3, uniformly grey; (E) pattern 4, uniformly white. Specimen vouchers: (A) BORNEENSIS 12560 from Mahua; (B) BORNEENSIS 12512 from Mahua; (C) BORNEENSIS 23302 from Wario; (D) BORNEENSIS 23340 from Wario; BORNEENSIS 12810 from Ulu Senagang.

Figure 7. Adults and larvae of three Meristogenys species treated in this study. A, B, Meristogenys stigmachilus sp. nov. (BORNEENSIS 12512 and 03B1 from Mahua). C, D, Meristogenys stenocephalus sp. nov. (B12808 and 05B217 from Ulu Senagang). E, F, Meristogenys whiteheadi (B22971 and 05B209 from Wario). Scale bars: 10 mm.