Leptobrachella phiaoacensis, Luong & Hoang & Pham & Ziegler & Nguyen, 2023

Luong, Anh Mai, Hoang, Chung Van, Pham, Cuong The, Ziegler, Thomas & Nguyen, Truong Quang, 2023, Two new species of Leptobrachella Smith 1925 (Amphibia: Megophryidae) from Cao Bang Province, Vietnam, Zootaxa 5369 (3), pp. 301-335 : 309-312

Leptobrachella phiaoacensis sp. nov.

( Figs. 3 , 4 ; Tables 2–4 )

Holotype. Adult male IEBR A.5195 (field number: CB.2016.51), VIETNAM: Cao Bang Province, Nguyen Binh District, Phia Oac-Phia Den National Park (22°36'33.7"N 105°52'15.4"E, 1,630 m a.s.l.), collected by Hoang et al. on 13 July 2016.

Paratypes (n = 9). Four adult males IEBR A.5196–5199 (field numbers: CB.2016.39, 54, 60, 61); the same collection data as for the holotype . Five adult females IEBR A.5200–5204 (field numbers: PhiaOac.2018.3, 4, 59, 60, 61); VIETNAM: Cao Bang Province, Nguyen Binh District, Phia Oac-Phia Den National Park (22°36'39.4"N 105°52'29.0"E 1,530 m a.s.l.), collected by Hoang et al. in November 2018 .

Diagnosis. Leptobrachella phiaoacensis sp. nov. is distinguished from its congeners by a combination of the following morphological characters: size medium (27.8–33.3 mm in adult males and 31.5–41.8 mm in adult females); head longer than wide; tympanum distinct; dorsal skin shagreened with fine tubercles; toes webbing rudimentary, with narrow lateral fringes; supratympanic fold edged by a distinct black line; the presence of a dark brown triangle in interorbital region and a W-shaped marking in scapular region; belly from pinkish white to white with dark brown specking on belly periphery; iris bicolored copper in upper part, fading to silvery grey in lower part.

Description of holotype. Habitus stocky, size medium (SVL 32.2 mm), head longer than wide (HDL/HDW 1.05); snout obtusely pointed in dorsal view, slightly projecting beyond margin of lower jaw; nostril round, located closer to the tip of snout than to eye; canthus rostralis round; loreal region sloping; pupil vertical; eye diameter shorter than snout length (EYE/SNT 0.98); tympanum distinct, round, tympanum diameter smaller than that of eye (TMP/EYE 0.44), tympanic rim not elevated relative to skin of temporal region; vomerine teeth absent; pineal ocellus absent; vocal sac openings present; tongue large, broad, with small notch at tip; supratympanic fold forming a distinct ridge, running from posterior corner of eye towards axillary gland, with few nodules.

Forelimbs thin, slender; finger tips round, equal to phalange width; relative finger lengths: I<II<IV<III; nuptial pad absent; subarticular tubercles absent; a large, round inner palmar tubercle, distinctly separated from small, laterally compressed outer palmar tubercle; finger webbing absent and without lateral fringes.

Hindlimbs slender, tibia nearly half of snout-vent length (TIB/SVL 0.44); heels meeting when thighs adpressed at right angles to the body; tips of toes like those of fingers; relative toe lengths: I<II<V<III<IV; subarticular tubercles absent; inner metatarsal tubercle small, oval, pronounced, outer metatarsal tubercle absent; toes webbing rudimentary; toes with narrow lateral fringes.

Skin texture in life. Skin on dorsum shagreened with fine tubercles, denser in posterior part of the back; dorsal surface of thighs, upper arms and upper eyelid covered by small tubercles; around vent with large tubercles; ventral skin smooth; pectoral gland laterally compressed, 0.6 mm in diameter; femoral glands small, oval, approximately 0.8 mm in diameter, located on posteroventral surfaces of thighs, closer to knee than to vent; supra-axillary gland raised, 1.6 mm in diameter. Ventrolateral glands present, dorsolaterally compressed, forming a discontinuous line along the body.

Color in life. Dorsal surface of head and body purple pink, with a dark brown triangle in interorbital region and a distinct dark W-shaped marking in scapular region, dorsum with some dark brown markings; flank and heel greyish brown with some dark flecks; upper lip with dark brown bars; tympanum black, a dark brown stripe below supratympanic ridge, running from posterior corner of eye towards tympanum; dorsal surface of limbs with diffuse transverse dark brown bars; fingers and toes with faint transverse bars; throat, chest and belly pinkish white with dark brown specking on belly periphery; chin, thighs, arms and all of tibiotarsus brown with small whitish spots; supra-axillary gland cream; femoral, pectoral and dorsolateral glands white; iris bicolored, copper in upper half, fading to silvery grey in its lower half.

Color in preservative. Dorsal surface brown; throat, chest, and belly cream; ventral lateral margins of throat and belly with brown specking; ventral surface of thighs and arms cream with white specking; white pectoral glands became indistinct in preservative.

Variation. Measurements of the type series are shown in Table 2 and photographs of paratypes in life are shown in Fig. 4 . Specimens vary in body size and color pattern in life. Ground color of dorsal surface is purple pink (IEBR A.5195, A.5204) or brown (IEBR A.5200), belly is pinkish white (IEBR A.5195) or white (IEBR A.5204), the Wshaped marking is distinct (IEBR A.5195, A.5204) or discontinuous (IEBR A.5196–5199, 5200–5203). In preservative, dorsal skin texture varies from finely tuberculate to almost smooth. Glands around cloacal opening vary in size and number. Females (SVL 35.0± 4.2 mm, n=5) tend to have a larger body size than males (SVL 31.5± 2.2 mm, n=5).

Etymology. Specific epithet is in reference to the type locality, the Phia Oac mountain peak, which is one of two highest peaks in the Phia Oac-Phia Den National Park. Phia Oac Peak has an elevation of 1931 m a.s.l., making up the "roof" of the western part of Cao Bang Province. We recommend “Phia Oac Litter Frog” as the common English name and “Cóc mày phia oắc” as the Vietnamese name.

Distribution and ecological notes. Leptobrachella phiaoacensis sp. nov. is currently known from Phia Oac-Phia Den National Park in Cao Bang Province, Vietnam. All specimens of the new species were found, one on a rock and another one on the bank of a small cascade stream, in evergreen forest at elevations of 1,530 –1,630 m a.s.l. ( Fig.7A ). The surrounding habitat was secondary forest of large, medium, and small hardwoods mixed with shrubs and vines ( Fig. 7B ). Males were found while calling but without record. Leptobrachella phiaoacensis sp. nov. occurs sympatrically with L. ventripunctata , L. nyx and another new species of Leptobrachella (population B described below). Other amphibian species found at the sites included Quasipaa boulengeri (Günther) , Odorrana nasica (Boulenger) , Boulenophrys caobangensis (Nguyen, Pham, Nguyen, Luong & Ziegler) , and Limnonectes bannanensis Ye, Fei, Xie & Jiang.

Comparisons. Comparative morphological data of Leptobrachella phiaoacensis sp. nov. and 70 recognized Leptobrachella species occurring north of the Isthmus of Kra were showed in Table 3 .

In the phylogenetic tree Leptobrachella phiaoacensis sp. nov. is a sister taxon to L. flaviglandulosa (0.97 in BI, 71.9% in ML) ( Fig. 2 ), and it can be distinguished from the sister by genetic divergences of p=3.7–4.5% ( Table 4 ). Morphologically, the new species differs from L. flaviglandulosa by having a larger body size (SVL 27.8–33.3 mm vs. 23.0–27.0 mm of L. flaviglandulosa ), a W-shaped marking in scapular region in males (vs. “\ /”-shaped yellow marking in L. flaviglandulosa ), belly from pinkish white to white with dark brown specking on belly periphery (vs. belly creamy white with dark brown dusting along the margins in L. flaviglandulosa ), and iris bicolored: copper in upper part, fading to silvery grey in lower part (vs. golden-orange in upper half, fading to whitish grey in lower half in L. flaviglandulosa ).

Leptobrachella phiaoacensis sp. nov. differs from L. khasiorum by having a larger body size in males (SVL 27.8–33.3 mm vs. 24.5–27.3 mm in L. khasiorum ), and indistinct dorsolateral markings (vs. distinct in L. khasiorum ); from L. laui by having a larger body size in males (SVL 27.8–33.3 mm vs. 24.8–26.7 mm in L. laui ), and iris bicolored: copper in upper part, fading to silvery grey in lower part (vs. iris uniformly coppery orange with fine black reticulations throughout in L. laui ); from L. liui by having iris bicolored: copper in upper part, fading to silvery grey in lower part (vs. iris brownish in L. liui ), belly pinkish white with dark brown specking on belly periphery (vs. creamy white with dark brown spots on chest and margins in L. liui ), and toes with narrow lateral fringes (vs. wide lateral fringes in L. liui ); from L. mangshanensis by having a larger body size in males (SVL 27.8–33.3 mm vs. 22.2–27.8 mm in L. mangshanensis ), different ventral color pattern (belly from pinkish white to white with dark brown specking on belly periphery vs. reddish brown with white specking in L. mangshanensis ); from L. maoershanensis by having different ventral color pattern (belly from pinkish white to white with dark brown specking on belly periphery vs. creamy white with irregular black spots in L. maoershanensis ) and indistinct dorsolateral markings (vs. distinct dorsolateral markings in L. maoershanensis ); from L. yingjiangensis by having a larger body size in males (SVL 27.8–33.3 mm vs. 25.7–27.6 mm in L. yingjiangensis ) and toes with narrow lateral fringes (vs. wide lateral fringes in L. yingjiangensis ); from L. yunkaiensis by having different ventral color pattern (pinkish white to white with dark brown specking on belly periphery vs. pinkish with distinct or indistinct specking in L. yunkaiensis ) and toes with narrow lateral fringes (vs. wide lateral fringes in L. yunkaiensis ).

Figures

FIGURE. 3. Holotype of Leptobrachella phiaoacensis sp. nov. (IEBR A.5195): A) Lateral view and B) Ventral view in life, C) Dorsolateral view and D) Ventral view in preservative, E) Right food and F) Right hand. Scale bars = 10 mm. Photos by A.M. Luong.

FIGURE. 4. Variation of Leptobrachella phiaoacensis sp. nov. in life:A) Paratype (IEBR A.5200), B) Paratype (IEBR A.5201), C) Paratype (IEBR A. 5202), D) Paratype (IEBR A.5203), E) Dorsolateral view of Paratype (IEBR A.5204) and F) Ventral view of Paratype (IEBR A.5204). Photos by C.V. Hoang.

FIGURE. 7. A) Habitat of Phia Oac-Phia Den National Park in Cao Bang Province, Vietnam, B) Microhabitat habitat of Leptobrachella phiaoacensis and C) Microhabitat habitat of Leptobrachella phiadenensis. Photos by C.T. Pham and C.V. Hoang.

FIGURE. 2. The Bayesian inference (BI) tree based on the partial 16S rRNA mitochondrial gene. Values at nodes correspond to BI/ML support values, respectively. Leptobrachium cf. chapaense and Xenophrys truongsonensis are used in the outgroup.