Leptobrachium xanthops, Stuart, Bryan L., Phimmachak, Somphouthone, Seateun, Sengvilay & Sivongxay, Niane, 2012

Stuart, Bryan L., Phimmachak, Somphouthone, Seateun, Sengvilay & Sivongxay, Niane, 2012, A new Leptobrachium (Anura: Megophryidae) from the highlands of southeastern Laos, Zootaxa 3155, pp. 29-37 : 33-35

Leptobrachium xanthops sp. nov.

Holotype. NCSM 78468 (field tag BLS 14376), adult male ( Figure 3 ), Laos, Dakchung Plateau, Phou Ajol Mountain, Xe Kong Province, Dakchung District, 15.68239°N 107.19424°E, 1,475 m elev., coll. 18 May 2011 by Bryan L. Stuart, Somphouthone Phimmachak, and Sengvilay Seateun.

Paratypes. Two adult females: NCSM 78466, same data as holotype except coll. 17 May 2011; NCSM 78467, same data as holotype except coll. 15.68516°N 107.19814°E, 1,450 m elev., 17 May 2011. One subadult female: NUOL 0 0 0 0 1, same data as holotype except coll. 15.68444°N 107.19689°E, 1,500 m elev., 19 May 2011.

Referred material. One metamorph: NCSM 78469, same data as holotype except coll. 15.68477°N 107.19407°E, 1,490 m elev.

Etymology. The specific epithet taken from xanthos Gr. for yellow and ops Gr. for eye, in reference to the iris color of the new species.

Diagnosis. Assigned to the genus Leptobrachium on the basis of having head width longer than shank length; skin above with a network of ridges; large axillary glands; extremities of digits rounded; and upper part of iris colored differently from lower part ( Dubois & Ohler 1998). A small-sized Leptobrachium having males with SVL 44.7, females with SVL 38.8–45.2; lower one-half of iris dark brown, upper one-half of iris pale yellow, scleral arc pale yellow; dark venter (purplish-gray in preservative) with minute white spots on tubercles; and sexually active males without spines on the upper lip.

Description of holotype. Habitus moderately stocky; body tapering to groin. Head broad and depressed; head length slightly longer than head width. Snout rounded in dorsal view, sharply sloping in profile, barely projecting beyond lower jaw in profile; nostril slightly closer to tip of snout than to eye, below canthus, internarial shorter than interorbital distance; canthus rostralis distinct; lores oblique, moderately concave; eye large, slightly projecting from side of head, diameter shorter than snout length, interorbital distance subequal to upper eyelid width; no pineal ocellus; tympanum round, slightly elevated from side of head, annulus weakly visible, tympanum diameter about 40% eye diameter and greater than distance between tympanum and eye; tongue heart-shaped, notched posteriorly; large, slit-like vocal sac openings on floor of mouth near lateral margin of tongue; vomerine teeth absent; testes mature.

Forelimb slender. Fingers moderately slender, without webbing. Tip of fingers blunt, that of fingers I slightly swollen; relative finger lengths II <IV <I <III; two oval palmar tubercles in contact, inner larger than outer, low callous bumps on ventral surface of fingers; nuptial pad absent.

Hindlimb slender and relatively short. Toes moderately slender; webbing on toe I and preaxial side of toe II to level of distal margin of subarticular tubercle, on postaxial side of toe II to base of tip, on preaxial side of toe III to level of proximal subarticular tubercle continuing as a fringe to base of tip, on postaxial side of toe III to midway between proximal subarticular tubercle and tip continuing as a fringe to base of tip, on preaxial and postaxial sides of toe IV to same level as postaxial side of toe III and continuing as a fringe to base of tip, and on toe V to subarticular tubercle continuing as a fringe to base of tip. Tips of all toes blunt, slightly swollen; relative toe lengths I<II<V<III<IV; distinct, oval, inner metatarsal tubercle, length about 75% distance between tip of toe I and tubercle; no outer metatarsal tubercle.

Skin above smooth with fine network of ridges, with small tubercles above sacrum; no spines on upper lip; low supratympanic ridge from posterior edge of eye to axilla; ventrally granular, skin smooth on ventral surfaces of limbs; large, round axillary gland on ventrolateral surface slightly posterior to insertion of forelimb with body; indistinct femoral gland on posteroventral surface of thigh, closer to knee than vent.

Color of holotype in life. Dorsum dark gray, with indistinct, black spots on tubercles, white spots on tubercles near vent; upper flank like dorsum, lower flank like belly, with small white spots at interface; upper surface of forelimb with narrow, indistinct black bands; upper surface of hindlimb with black bands and indistinct bronze bands on dorsal surface of thigh, black and light gray bands on dorsal surface of tibiotarsus and foot; lower one-half of iris dark brown, upper one-half of iris pale yellow, scleral arc pale yellow (visible in the posterior corner of the eye and when the palpebrum is retracted); irregular, black streak under canthus and supratympanic fold; ventral surface of body and limbs dark purplish-gray, chin and chest lighter than belly, minute white spots on tubercles on chin, chest, and belly; axillary and femoral glands white.

Color of holotype in preservative: Color in preservative almost uniformly dark gray-brown, with only faint traces of banding on hindlimb visible. Upper part of iris and scleral arc faded to white.

Variation: Paratypes closely resemble the holotype, except NCSM 78466 had indistinct bronze bands on forelimb in life. Females with thinner forelimbs than males. Females NCSM 78466–67 with large, brown ova in preservative, female NUOL 0 0 0 0 1 with developing creamy-white ova in preservative. Measurements are summarized in Table 1 .

Molecules. The holotype and two paratypes (NCSM 78466, NUOL 00001) are identical in the 16S gene fragment, but are divergent from topotypes of other Leptobrachium species known from southern Laos and adjacent central Vietnam. Specifically, the new species has an uncorrected pairwise divergence of 8.01% from L. banae , 4.01% from L. buchardi , 11.66% from L. chapaense , 3.06% from L. ngoclinhense , 3.09% from L. pullum , and 6.57% from L. xanthospilum (Table 2).

Distribution and natural history. Leptobrachium xanthops is known with certainty only from wet evergreen forest at 1,450–1,500 m elevation on the Dakchung Plateau, Phou Ajol Mountain in Xe Kong Province, Dakchung District, Laos. The species probably occurs elsewhere in the highlands of southeastern Laos and adjacent central Vietnam, and may be hidden in existing natural history collections under previously named species of Leptobrachium . The adults were found at night (1905–2215 h) on leaf litter within 15 m of 3–5 m wide swift, rocky streams. Calling was not heard. The subadult was taken at night (2000 h) on leaf litter away from water. The metamorph was found at night (2110 h) on a stone in shallow water at the bank of a 5 m wide swift, rocky, cascading stream.

Comparisons. Leptobrachium xanthops differs from all other species of Leptobrachium by having a pale yellow upper one-half of the iris and scleral arc. It further differs from all other species of Leptobrachium that occur in Laos, Vietnam, or Cambodia (Table 2) in size, body coloration, and/or male secondary sexual characters. Specifically, L. ailaonicum , L. echinatum , and L. ngoclinhense have males with SVL> 60 (44.7 in L. xanthops ) and spines on the upper lip (absent in L. xanthops ). Leptobrachium banae and L. xanthospilum have males with SVL> 57 (44.7 in L. xanthops ) and females with SVL> 80 (50.3–56.9 in L. xanthops ). In addition, L. banae has red bands on the limbs (absent in L. xanthops ) and L. xanthospilum has large, yellow, glandular spots on the flank (absent in L. xanthops ). Leptobrachium buchardi , L. pullum , and L. smithi have light venters with dark spots (dark purplish-gray venter in L. xanthops ), and L. leucops has distinct dark markings on the dorsum and banding on the limbs (absent in L. xanthops ). Leptobrachium chapaense , L. mouhoti , and L. promustache have males with SVL> 51 (44.7 in L. xanthops ) and females with SVL> 58 (50.3–56.9 in L. xanthops ), and L. promustache has males with spines on the upper lip (absent in L. xanthops ).

Figures

FIGURE 3. Leptobrachium xanthops sp. nov. in life. (A) Lateral view, (B) eye with palpebrum retracted, (C) dorsal view, and (D) ventral view of the male holotype NCSM 78468. (E) Lateral view and (F) ventral view of the female paratype NCSM 78467. The upper iris and scleral arc are pale yellow in life, but appear near to white under camera flash.