Microhyla roedderi, Hoang & Pham & Nguyen & Phan & Ziegler & Orlov & Jiang & Do, 2025

Microhyla roedderi sp. nov.

LSID: urn:lsid:zoobank.org:act:0299FDAF-0B60-4FF6-A2AC-F34550C27F42

( Figs. 4 View FIGURE 4 , 5 View FIGURE 5 ; Table 2 View TABLE 2 , Table supplement 2)

Holotype. Adult male IEBR A.6271 (Field number KH2022.26), collected by D.T. Do et al. on 8 April 2022 in Van Ninh District, Khanh Hoa Province, Vietnam (12°49'49.0"N 109°11'55.8"E, at an elevation of 784 m a.s.l.). GoogleMaps

Paratypes (n= 12). Nine adult males IEBR A.6272–6280 (Field numbers KH2022.25, KH2022.28, KH2022.29– 35) and GoogleMaps two adult females IEBR A.6281,.6282 (Field numbers KH2022.24, KH2022.27), collection data the same as the holotype GoogleMaps ; one adult female IEBR A.6283 (Field number PY2022.67), collected in Tay Hoa District , Phu Yen Province, Vietnam (12°51'31.0"N 109°12'55.2"E, at an elevation of 433 m a.s.l., collected by D.T. Do et al. on 5 April 2022. GoogleMaps

Diagnosis. Microhyla roedderi sp. nov. is distinguished from other species of the subgenus Nanohyla by a combination of the following characters: Size medium (SVL 15.88–17.00 mm, n= 10 in males; 20.74–21.33 mm, n= 3 in females); body habitus slender; snout bluntly round; tympanum hidden; canthus rostralis round, distinct; loreal region oblique, weakly concave; dorsal skin slightly bumpy with low tubercles, slightly concentrated on dosolateral area, scattered over dorsal surface of limbs and upper eyelid; ventral surface smooth; mid vertebral skin ridge and dorsomedial stripe absent; superciliary tubercles absent; supratympanic fold weakly developed; fingers slender, free of webbing, with weak skin fringes on all fingers; finger I reduced slightly, less than half of finger II in length, males without nuptial pad; grooves on dorsal surface of disks present in fingers II–IV; two round, flat palmar tubercles; hindlimbs long, tibiotarsal articulation of adpressed limb reaching well beyond snout; toe webbing formula I1–2II1–2III1–2IV2–1V; inner metatarsal tubercle oval; outer metatarsal tubercle absent; dorsal surface of head and trunk greyish brown to light brown with dark brown markings, a distinct light brown interorbital bar between eyelids, a>–<shape marking running from the eyelids to the groin; few small black spots on the flank and in the inguinal region; two small black spots in the groin region; belly and limbs ventrally lighter with white marbling; pupil black, iris copper in life.

Description of holotype. Size medium (SVL 17.0 mm); habitus slender, head longer than wide (HL/HW 1.01); snout bluntly rounded, slightly protruding beyond margin of lower jaw, longer than diameter of eye (SL/ED 1.03); eyes protuberant, pupil round; dorsal surface of head flat; canthus rostralis round, distinct; loreal region oblique, weakly concave; nostril round, lateral, on canthus rostralis, closer to tip of snout than to eye (NED/SL 0.56); interorbital distance wider than internarial distance (IOD/IND 1.50), twice broader than upper eyelid (IOD/UEW 2.16); tympanum hidden, supratympanic fold weakly developed, from posterior corner of eye to arm insertion; vomerine teeth absent, tongue round posteriorly, free at the rear half of its length; slit like openings to a median vocal sac.

Forelimbs shorter than snout-vent length (FLL/SVL 0.85); hand shorter than a half of forelimb length (HAL/ FLL 0.43); fingers slender, free of webbing, with weak dermal fringes on all fingers; finger I reduced notably, less than half the length of finger II (1FLO/2FLO 0.29); nuptial pad absent; finger II slightly longer than finger IV (2FLI/4FLI 1.04), much shorter than finger III (2FLI/3FLI 0.69); relative finger lengths: I<IV<II<III; tip of finger I round, not enlarged; narrow peripheral grooves absent on all fingers; grooves on dorsal surface of disks present in fingers II, III, IV, absent in finger I; relative finger disk widths IV<II<III; subarticular tubercles on fingers distinct, round, formula 1:1:2:1 (given for fingers I:II:III:IV, respectively); two round, flat palmar tubercles.

Hindlimbs slender, almost twice as long as snout-vent length (HLL/SVL 1.98), tibia longer than half of snout-vent length (TL/SVL 0.65); tibiotarsal articulation reaching beyond snout when limb adpressed along body; foot longer than tibia (FL/TL 1.39); relative toe lengths: I<II<V<III<IV; tarsus smooth, inner tarsal fold absent; tips of all toes slightly dilated, forming truncated disks, disks of all toes with peripheral grooves, dorsal surface of toe disks II, V with short median longitudinal grooves; relative toe disk widths: I<IV<V<II<III; webbing formula I1–2II1– 2III1–2IV2–1V; subarticular tubercles on toes distinct, round, formula 1:1:2:3:2 (for toes I:II:III:IV:V, respectively); inner metatarsal tubercle oval; outer metatarsal tubercle absent.

Dorsal skin bumpy with low tubercles, slightly concentrated on the dorsolateral area, scattered over dorsal surface of limbs and upper eyelid; supratympanic fold weakly developed, from posterior corner of eye to arm insertion; lateral side of head and flank smooth; ventral side of body and limbs smooth, vent area smooth.

Coloration in life. Dorsal surface of head and trunk greyish brown to light brown with dark brown markings, a distinct light brown interorbital bar between eyelids, a>–<shape marking running from the eyelids to the groin; few small black spots on the flank and in the inguinal region; two small black spots in the groin region; supratympanic fold light brown; dorsolateral surface of arm and fingers dark brown with a small black bar near the wrist; dorsal surface of thigh, tibia, tarsus and toes brown with dark brown cross bars; throat and chest brownish grey with intense small white mottling, belly and limbs ventrally lighter with white marbling; pupil black, iris copper ( Fig. 4 View FIGURE 4 ).

Coloration in preservative. In ethanol, dorsal coloration changed to dark greyish brown, ventral surface of chest, belly, and limbs greyish beige; dorsal pattern, dark spots on dorsum and stripes on dorsal surfaces of limbs unchanged, dark brown pattern changed to dark grey; iris completely black ( Fig. 5 View FIGURE 5 ).

Variation. Type specimens vary in body size. Three female paratypes have a larger body size than those of ten males ( SVL 20.95 ± 0.33 mm [20.74–21.33 mm; n=3] vs. 16.43± 0.35 mm [15.88–17.00 mm; n=10] in males). Dark brown marking on dorsum is more distinctly lobed in two paratypes ( IEBR A.6281, A.6283). Black spots in the flank and inguinal region are various in size (smaller in IEBR A.6283). For more details see Table 2 View TABLE 2 and Fig. 6 View FIGURE 6 .

Natural history. Specimens were collected at night, from 19:00 to 23:00 h, on the ground nearby streams in evergreen forest. The surrounding habitat was evergreen forest with large, medium and small hardwoods mixed with shrubs and vines ( Fig. 7 View FIGURE 7 ), at elevations between 433 and 784 m a.s.l. Air temperatures at the sites ranged from 20.5–28.5 oC and relative humidity was 60–80%. Other amphibian species found at the sites included Limnonectes limborgi (Sclater) , Limnonectes poilani (Bourret) , Hylarana sp. , Odorrana cf. banaorum (Bain, Lathrop, Murphy, Orlov & Ho) , Kurixalus sp. , and Hylarana attigua (Inger, Orlov & Darevsky) . Larval stages and eggs of the new species are unknown.

Comparison. Microhyla roedderi sp. nov. most closely resembles M. nanapollexa in morphology, the close relationship being supported by molecular phylogenetic position ( Fig. 1 View FIGURE 1 , Table 3 View TABLE 3 ). However, the new species differs from the latter by having a larger body size (SVL 15.98–17.00 mm in males, 20.74–21.33 mm in females vs. SVL 15.43 mm in male, 16.02–16.60 mm in females of M. nanapollexa ); dorsal skin bumpy with low tubercles, concentrated on the dorsolateral area, scattered over the dorsal surface of limbs and upper eyelid ( Figs. 4A View FIGURE 4 ; 6A; 6B View FIGURE 6 ) (vs. skin on dorsum relatively smooth with low, round tubercles concentrated on the outer edge, flanks, below and posterior to eye in M. nanapollexa ( Fig. 2A View FIGURE 2 ); finger I reduced notably, less than half the length of finger II ( Fig. 8B View FIGURE 8 ) (vs. partially free nub just proximal to finger II in M. nanapollexa ( Fig. 8A View FIGURE 8 ); different webbing formula I1–2II1–2III1–2IV2–1V (vs. I1–2II1–2½III2½–2½IV 2½–1V in M. nanapollexa ) ( Table S1 View TABLE 1 ); dorsal surface of head and trunk greyish brown to light brown with dark brown markings, a distinct light brown interorbital bar between eyelids, a>–<shape marking running from the eyelids to the groin (vs. dorsal surface of greyish brown to light brown with a dark brown or brown spear shape marking, running from the posterior eyes to the groin in M. nanapollexa ); and few small black spots on the flank and inguinal region (vs. a black broken streak below dorsolateral folds in M. nanapollexa ).

Microhyla roedderi sp. nov. differs from other known species in the subgenus Nanohyla by having a larger body size (SVL 15.88–17.00 mm in males, 20.74–21.33 mm in females vs. SVL 13.6–14.7 mm in males, 18.3–18.63 mm in females of M. hongiaoensis ; vs. SVL 14.4–15.6 mm in males, 18.2–18.4 mm in females of M. annectens ; vs. SVL 13.2–15.0 mm in males, 15.9–17.0 mm in females of M. arboricola ; vs. SVL 10.5–11.9 mm in males, 12.4–14.5 mm in females of M. perparva ; vs. SVL 13.9–16.2 mm in males, 15.1–17.8 mm in females of M. petrigena ); by having a smaller body size (SVL 15.9–17.0 mm in males, 20.7–21.3 mm in females vs. SVL 18.2–20.2 mm in males of M. albopunctata ; vs. SVL 18.8–21.5 mm in males, 21.1–23.2 mm in females of M. marmorata ); by having snout bluntly round (vs. pointed in M. arboricola ; obtusely pointed in M. perparva , M. petrigena ); by having dorsum skin slightly bumpy (vs. smooth in M. annectens , M. perparva , M. pulchella ); by having FI <½ FII (vs. nub or bulge in M. perparva , M. petrigena ); by having dorsal median longitudinal grooves on finger disks present (vs. absent in M. hongiaoensis ); by having one metatarsal tubercle (vs. two metatarsal tubercles in M. albopunctata , M. annamensis , M. hongiaoensis , M. marmorata ); by superciliary tubercles absent (vs. superciliary tubercles present in M. perparva ).

Distribution. Microhyla roedderi sp. nov. is currently known only from the type locality in Deo Ca Mountain, Khanh Hoa and Phu Yen provinces, Vietnam, at elevations between 433 and 784 m a.s.l.

Conservation status. Microhyla roedderi sp. nov. is likely to be endemic to Deo Ca Mountain, central Vietnam. However, the extent of its actual distribution range should be confirmed in further studies. Given the available information, we suggest this species be considered as Data Deficient following IUCN’s Red List categories ( IUCN 2001).

Etymology. The new species is named after Ass. Prof. Dr. Dennis Rödder, Leibniz Institut zur Analyse des Biodiversitätswandels (LIB) / Zoologisches Forschungsmuseum Alexander Koenig (ZFMK), Bonn, to honour his long-term support of conservation-based research including the support of student work and providing his expertise in species distribution modelling. We recommend “Roedder’s Narrow-mouth Frog” as the common English name and “Nhái bầu roedder” as the Vietnamese name.