Micryletta hekouensis, Liu & Hou & Mo & Rao, 2021

Liu, Shuo, Hou, Mian, Mo, Mingzhong & Rao, Dingqi, 2021, A new species of Micryletta Dubois, 1987 (Anura, Microhylidae) from Yunnan Province, China, Herpetozoa 34, pp. 131-140 : 131

Micryletta hekouensis sp. nov.

Figures 3 , 4 , 5

Type material.

Holotype. KIZ20210510, adult male from Nanxi village, Nanxi Town, Hekou County, Honghe Prefecture, Yunnan Province, China (22°38'17"N, 103°59'8"E, elevation 350 m a.s.l.), collected by Shuo Liu at 23:50 on 15 May 2021.

Paratype. KIZ20210511, adult female from the same locality as for the holotype, collected by Shuo Liu at 21:15 on 17 May 2021.

Diagnosis.

Micryletta hekouensis sp. nov. can be distinguished from its congeners by a combination of the following characters: small-sized within genus (SVL 20.5-20.8 mm); areas above canthus rostralis, upper eyelids, areas posterior to eyelids, and dorsum of upper arms golden, other parts of dorsum almost solid black or yellowish grey with brownish black stripes; lateral sides of head and body black or yellowish grey, a white stripe from lower front of eye along upper lip back to anterior forelimb insertion; ventral side of body and limbs pink brown, chin region in adult males brownish black, small and irregular white marbling patterns on chest and lateral belly; supratympanic fold indistinct; outer metatarsal tubercle absent; webbing between toes absent; tibiotarsal articulation adpressed limb reaching level of front of eye.

Description of holotype.

Adult male. SVL 20.5 mm; habitus relatively slender; head small and triangular, slightly wider (HW 6.9 mm) than long (HL 6.5 mm); snout (SL 2.9 mm) abruptly rounded in dorsal view and slightly acuminate in profile, projecting beyond margin of lower jaw; eyes relatively small, slightly protuberant, pupil oval, transverse, eye diameter (EL 2.5 mm) approximately equal to interorbital distance (IOD 2.4 mm). Top of head flat, canthus rostralis rounded and distinct; loreal region weakly concave; nostril round, closer to tip of snout than to eye; interorbital distance (IOD 2.4 mm) greater than internarial distance (IND 2.0 mm) and upper eyelid width (UEW 1.7 mm). Tympanum rounded, small (TMP 0.6 mm) and distinct; supratympanic fold very indistinct. Choanae rounded; vomerine teeth absent; opening of vocal sac long cleft; tongue slender, with no notch at posterior tip.

Forelimbs slender (FLL 14.9 mm), lower arm and hand length (LAL 10.9 mm) more than a half of snout-vent length (LAL/SVL 0.53). Fingers slender with no webbing, rounded in cross-section, no lateral fringes; first finger well-developed, second finger slightly shorter than fourth, relative finger lengths: I<II<IV<III; tips of fingers round and not dilated; subarticular tubercles on fingers distinct, rounded and prominent, formula 1, 1, 2, 2; supernumerary tubercles on palm present and developed; three metacarpal tubercles, inner one rounded and smallest (IPTL 0.4 mm), median one (MPTL 0.7 mm) rounded and almost directly in front of elongated outer one (OPTL 0.8 mm); two rounded and one elongated prominent supernumerary palmar tubercles on the base of fingers II-IV, respectively, slightly larger than inner metacarpal tubercle; nuptial pad absent.

Hindlimbs slender and long (HLL 33.3 mm), more than two times longer than forelimbs (HLL/FLL 2.23); tibia (TL 10.9 mm) slightly shorter than one-third of hindlimb length; tibiotarsal articulation of adpressed limb reaching level of front of eye; foot (FL 11.4 mm) slightly longer than tibia. Relative toe lengths: I<II<V<III<IV; tarsus smooth, tarsal fold absent; tips of toes round and not dilated, slightly wider than those of fingers; webbing between toes absent; subarticular tubercles on toes oval and prominent, formula: 1, 1, 2, 3, 2; dermal ridges present under 2nd to 4th toes but indistinct; inner metatarsal tubercle oval, prominent, and small (IMTL 0.7 mm); outer metatarsal tubercle absent.

Dorsal skin smooth above, scattered with tiny and flat tubercles on dorsum of body, flanks, and hindlimbs; subtle longitudinal median ridge present on dorsum; dorsolateral fold absent; lateral sides of head smooth; ventral skin of body and limbs smooth.

Coloration of holotype in life.

Areas above canthus rostralis, upper eyelids, areas just posterior to eyelids, dorsum of upper arms, and areas above tibiotarsal articulation golden; other parts of dorsum of body black with two indistinct parallel longitudinal grey stripes on back; other parts of dorsum of limbs black mottled with gray and yellow. Lateral sides of head and body black, from lower front of eye along upper lip back to anterior forelimb insertion white; one indistinct longitudinal grey stripe on each side of body. Ventral side of body and limbs pinkish brown, chin region brownish black; small and irregular white marbling patterns on chest and lateral belly; some small white spots on lower lip. Iris bicolored, with upper third bronze and lower two-thirds brownish black.

Coloration of holotype in preservative.

Colors faded; areas above canthus rostralis, upper eyelids, and areas just posterior to eyelids turned to dark grey; dorsum of upper arms turned to pink; ventral side turned to yellowish white with light gray marbling on chest and lateral sides of belly; colors of other parts of body almost the same as in life.

Variation.

The female paratype is quite similar in appearance to the holotype (Table 3 ), but show some variations in coloration. The female paratype has a relatively lighter body color, areas above canthus rostralis, upper eyelids, areas posterior to eyelids, and dorsum of upper arms are golden, the same as holotype; however, midline of the back is brownish black, one discontinuous black stripe dorsolateral on each side, lower parts of flanks greyish brown; other parts of dorsal and lateral body are yellowish grey; dorsa of lower arms and hindlimbs brownish grey with larger and more obvious irregular yellow spots. The color of the ventral side is similar to that of the holotype, except that the chin region is not brownish black but light yellow.

Sexual dimorphism.

Male has opening of vocal sac and single hypopharyngeal vocal sac, female has no vocal sac and opening of vocal sac. Besides this, there is no significant morphological character difference between males and females.

Etymology.

The specific epithet Micryletta hekouensis refers to Hekou County, the type locality of the new species. We propose "Hekou Paddy Frog" for the common English name and “河口小姬蛙” ( Hé Kǒu Xiǎo Jī Wā) for the common Chinese name of the new species.

Natural history.

Specimens of the new species were found in the grass on the ground at night. Once startled, they jumped away quickly. The collection site is surrounded by primary broad-leaved forest and bamboo. There are karst rocks nearby, no water body within a few hundred meters, and no courtship calls were heard. The collection site is in the nature reserve and the environment is not destroyed; this species is not threatened at present (Figure 6 ).

Distribution.

This species is currently known only from the type locality, Nanxi Town, Hekou County, Honghe Prefecture, Yunnan Province, China. It is expected to be found in neighboring Northern Vietnam.

Comparisons.

Micryletta hekouensis sp. nov. differs from M. aishani by relatively smaller body size (SVL 20.5-20.8 mm vs. 22.1-27.3); snout abruptly rounded in dorsal view and slightly acuminate in lateral view (vs. snout shape nearly truncate in dorsal view and acute in lateral view); dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum brown to reddish brown with several blackish brown spots present on posterior parts of back and near groin); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to armpit).

Micryletta hekouensis sp. nov. differs from M. dissimulans by dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum reddish brown with merging irregular shaped brown blotches edged in beige); flanks black or greyish brown (vs. large black spots on flanks and axillary and inguinal areas present); white stripes on upper lips present (vs. absent); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to tympanum).

Micryletta hekouensis sp. nov. differs from M. erythropoda by relatively smaller body (SVL 20.5-20.8 mm vs. up to 30 mm); dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum gray or beige to saturated ochre or brick red, dark contrasting round or irregular shape spots irregularly scattered throughout the dorsum); venter without dark patterns (vs. with relatively distinct dark and light marbled speckling); outer metatarsal tubercle absent (vs. present); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to posterior edge of tympanum).

Micryletta hekouensis sp. nov. can be distinguished from M. immaculata by relatively smaller body (SVL 20.5-20.8 mm vs. up to 23.3-30.1 mm); dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum bronze brown to reddish brown without dark patterns); supratympanic fold indistinct (vs. distinct); supratympanic fold indistinct (vs. distinct); webbing between toes absent (vs. basal and poorly developed); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to tympanum).

Micryletta hekouensis sp. nov. can be distinguished from M. inornata sensu stricto from Sumatra, Indonesia, and from Tanintharyi, Myanmar, by dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum brownish grey with irregular blackish brown blotches and blackish brown streak); ventral side of body and limbs pinkish brown or pinkish grey with small and irregular white marbling patterns on chest and lateral belly (vs. ventral side of body and limbs light reddish grey without mottling, nearly immaculate, or chin, chest, and lateral belly with a few dark marbling patterns); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to eye).

Micryletta hekouensis sp. nov. can be diagnosed from M. lineata by supratympanic fold indistinct (vs. distinct); venter pink brown with small and irregular white marbling patterns on chest and lateral belly (vs. venter beige with light brown mottling along throat); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to eye).

Micryletta hekouensis sp. nov. differs from M. nigromaculata by supratympanic fold indistinct (vs. distinct); dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum brown to reddish brown with dark brown irregular hourglass shaped pattern and two large dark inguinal spots); flanks black or greyish brown (vs. flanks greyish white with dark patches or spots); white stripes on upper lips present (vs. absent); chin region in males brownish black (vs. whitish with light-gray marbling); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to eye).

Micryletta hekouensis sp. nov. differs from M. sumatrana by supratympanic fold indistinct (vs. distinct); dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum golden brown scattered with black spots); dark cross bands on tibia and tarsus absent (vs. present); venter without dark patterns (vs. with dark brown and cream mottling).

Micryletta hekouensis sp. nov. differs from M. steinegeri by relatively smaller body (SVL 20.5-20.8 mm vs. up to 30 mm); dorsum almost solid black or yellowish grey with brownish black stripes (vs. dorsum dark gray to violet with irregular dark blotches or speckles); venter without dark patterns (vs. with grayish white and brown spots); webbing between toes absent (vs. rudimentary webbing); tibiotarsal articulation adpressed limb reaching level of front of eye (vs. reaching to tympanum).

Figures

Figure 3. Type series of Micryletta hekouensis sp. nov. in preservative. A. dorsal view; B. ventral view.

Figure 4. Close-up views of the hand and foot of the holotype (KIZ 20210510) of Micryletta hekouensis sp. nov. A. volar view of left hand; B. plantar view of left foot.

Figure 5. The holotype (KIZ 20210510) and the paratype (KIZ 20210511) of Micryletta hekouensis sp. nov. in life. A. dorsal view of the holotype; B. lateral view of the holotype; C. ventral view of the holotype; D. dorsal view of the paratype; E. lateral view of the paratype; F. ventral view of the paratype.

Figure 6. Habitat of Micryletta hekouensis sp. nov. at the type locality in Nanxi Town, Hekou County, Yunnan Province, China. A. The collection site; B. The surroundings of the collection site.