Leptolalax sp. 2

Dehling, Maximilian, 2012, Redescription of Leptolalax gracilis (Günther, 1872) from Borneo and taxonomic status of two populations of Leptolalax (Anura: Megophryidae) from Peninsular Malaysia, Zootaxa 3328, pp. 20-34 : 30-31

Leptolalax sp. 2

( Figure 6 )

Leptobrachium gracile — Boulenger 1908a

Megalophrys gracilis — Boulenger 1908b (partim), Boulenger 1912 (partim)

Megophrys gracilis — Smith 1930 (partim)

Leptobrachium gracilis — Inger 1966 (partim)

Referred material: BMNH 1906.2.28.59, 1906.2.28.60, two juveniles, collected by H. C. Robinson at Gunung Tahan, Pahang, Peninsular Malaysia, at 5200 ft. (ca. 1585 m).

Description: The specimens are not fully metamorphosed juveniles with remains of the tail. Basic measurements are given in Table 3 . With respect to their developmental stage the specimens are comparatively large.

Habitus slender; head moderately broad, about as wide as long and as wide as the trunk; snout acuminate in ventral view, rounded in profile; canthus rostralis distinct, almost straight-lined in both dorsal and lateral view; loreal region oblique, slightly concave; nostrils rounded, directed laterally; tympanum distinct, rounded, its diameter two-fifth the eye diameter (TD/ED 0.41); interorbital distance less than upper eyelid width (IO/EW 0.95–0.97); symphysial knob on anteriormost part of mandible; vomerine ridge and teeth absent; tongue large, broad, bifid, free for about half its length; median lingual process absent.

Fore limbs slender; fingers long and slender, without webbing or lateral fringes of skin; relative length of fingers II<I<IV<III; finger tips rounded and slightly thickened; subarticular tubercles indistinct; large, rounded, prominent tubercle in thenar and metacarpal region of fingers I and II, smaller one in metacarpal region of fingers III and IV, separated from each other by distinct groove.

Hind limbs moderately long (LEG/SVL 1.65–1.71); tibiofibula moderately long (TFL/SVL 0.53–0.56); heels overlapping each other considerably when knees are flexed and thighs are held laterally at right angle to body; toe tips rounded and slightly thickened, smaller than finger tips; toe webbing rudimentary; fringes of skin on lateral sides of toes absent; relative length of toes I<II<V<III<IV; subarticular tubercles indistinct; longitudinal ridges of thickened skin on the plantar side of phalanges of toes hardly discernible; inner metatarsal tubercle small, slightly longer than wide; outer metatarsal tubercle absent.

Skin on dorsum and dorsal side of head smooth, weakly wrinkled on dorsal surfaces of the extremities; supratympanic fold thick and conspicuous, curved, running from posterior margin of eye to just behind corner of mouth; ventral side smooth; pectoral glands very large and conspicuous, at the insertion of the forelimbs; supraaxillary glands, ventrolateral, and femoral glands absent.

Colouration in preservative: Dorsal colouration light brown with dark brown pattern; pattern consisting of large, T- or cross-shaped blotch between and on upper eyelids, smaller blotch on snout, and many dark, light-centred spots on dorsum and on lateral surfaces; dorsal surfaces of the extremities, including the upper arm crossbanded; on tibia, bands replaced by similarly coloured, large blotches; all dorsal pattern elements having light, cream-coloured margin; ventral side finely speckled; chin region, especially edge of lower jaw, more densely pigmented and appearing darker than venter.

Ecological notes: The only information available was given by the collector of the specimens, H. C. Robinson, who stated that the specimens were collected at night among the stones of a rapid mountain stream and that they were extremely active and difficult to capture, and on the least alarm leaped into the water ( Boulenger 1908a).

Comparisons: The only known specimens of this taxon are not fully metamorphosed juveniles. They were assigned to L. gracilis from Borneo at a time when only the single holotype of this species was known ( Boulenger 1908a). Although they are juveniles and therefore cannot be compared to adult specimens without reservation, there are a number of characters that disqualify the specimens from Gunung Tahan for being conspecific with L. gracilis . The dorsal colouration of L. gracilis is variable but newer shows the conspicuous pattern of dark, lightmargined blotches and bands and dark, light-centred spots like the specimens from Gunung Tahan. The venter has large spots in L. gracilis (vs. finely mottled). The pectoral glands are very small, hardly discernible (vs. large and conspicuous), and the inner metatarsal tubercle is large and elongate, about two-fifths the length of the first toe (vs. small and roundish, slightly longer than wide, less then one-third of the length of first toe).

The Gunung Tahan specimens cannot be assigned unambiguously to any of the species of Leptolalax that have been reported from Peninsular Malaysia. L. heteropus has more developed toe webbing and distinct lateral fringes on the toes (vs. rudimentary webbing, lateral fringes indistinct) and is tentatively smaller with males having an SVL of 24.6–26.0 mm, female 31.7 mm (vs. 27.5–29.2 mm in juveniles). L. kajangensis has shorter legs with TFL/ SVL 0.42 (longer, TFL/SVL 0.53–0.56), a differing dorsal pattern, and an unpatterned venter (vs. finely mottled) ( Grismer et al. 2004). L. kecil is smaller with SVL of adult males being 19.3–20.5, of adult female 25.0 mm (vs. 27.5–29.2 mm in juveniles), has longer hindlimbs with LEG/SVL 1.74–1.81 (vs. 1.65–1.71), and an elongate, relatively larger inner metatarsal tubercle, being more than half as long as first toe (roundish, much smaller, less than one-third of length of first toe) ( Matsui et al. 2009). Leptolalax sp. 1 from Gunung Benom has a differing dorsal pattern and an unpatterned venter (vs. finely mottled), a relatively larger interorbital distance, its snout is rounded in ventral view (vs. acuminate) and truncate in profile (vs. rounded), and the metamorphic size is smaller (SVL 24.1 mm vs. 27.5–29.1 mm). L. pelodytoides has much more developed webbing and very conspicuous lateral fringes on the toes (indistinct), has a ventrolateral glandular ridge, supraaxillary and femoral glands (absent) and a smaller pectoral gland, and chin and venter are unpatterned (finely mottled). L. solus is tentatively smaller (SVL of only known adult male 27.6 mm vs. 27.5–29.1 mm in metamorphosing juveniles), has a differing dorsal pattern, a relatively larger inner metatarsal tubercle that is more than half the length of first toe (less than one-third), and more developed toe webbing ( Matsui 2006). To clarify the taxonomic status of the population from Gunung Tahan additional specimens, especially adults, need to be collected.

Figures

FIGURE 6. Dorsal view (left) and ventral view (right) of juveniles of Leptolalax sp. 2 from Gunung Tahan, Peninsular Malaysia (BMNH 1906.2. 28.59 [left] and 1906.2. 28.60 [right]).

Tables

TABLE 3. Measurements of juvenile specimens of Leptolalax sp. 2 from Gunung Tahan, Peninsular Malaysia (in mm). For abbreviations see Material and methods.

BMNH	1906.2.28.59		1906.2.28.60
measurement	absolute	divided by SVL	absolute	divided by SVL
SVL	29.2	1.0 0	27.5	1.0 0
HW	9.2	0.32	8.3	0.30
TFL	15.4	0.53	15.3	0.56
LEG	48.3	1.65	46.6	1.71