More dwarfs: a new microendemic species of Vietnamophryne (Anura, Microhylidae) from limestone karst of Quang Tri Province, Central Vietnam

A new species of the genus Vietnamophryne is described from limestone karst forests of Quang Tri Province, central Vietnam, based on two adult male specimens and integrative analyses of morphology and mitochondrial DNA. Morphologically, Vietnamophryne abscondita sp. nov. is distinguished from other congeners by the following combination of characters: (1) medium body size (snout-vent length 18.1–19.0 mm in males, n = 2); (2) head slightly wider than long; (3) snout short, rounded in dorsal view; (4) tympanum indistinct; (5) dorsal skin finely shagreened, lacking enlarged tubercles or a median dorsal ridge; (6) Finger I longer than half of Finger II; (7) toes without webbing, bearing rounded terminal discs; (8) forelimbs and hindlimbs slender; (9) dorsum dark brown to chocolate brown, with irregular lighter mottling; (10) flanks and limbs densely speckled with pale spots; (11) ventral surface bright yellow-orange to orange on chest and belly, with dark marbling on throat and ventral surfaces of limbs; (12) lower jaw region with scattered pale blotches; and (13) indistinct pale yellow suborbital spotting extending from the eye toward the mouth corner. Phylogenetic analyses based on the long mtDNA fragment recover Vietnamophryne abscondita sp. nov. as a well-supported independent lineage, showing uncorrected p-distances exceeding 3% from all currently recognized congeners of Vietnamophryne, based on the 16S rRNA gene fragment. Although shallow genetic divergences and limited sampling complicate species boundaries within the genus, further taxonomic changes are not proposed, and current species limits are considered provisional pending comprehensive integrative revision. The discovery of this species, together with a closely related undescribed lineage from the same province, highlights the underestimated diversity of Vietnamophryne and emphasizes the Annamites (Truong Son Mountains) as a priority region for future herpetological surveys.