Green Horned Toad Found in Xizang’s Grand Canyon

Researchers have identified a previously undescribed lineage of Asian horned toad from the Yarlung Tsangpo Grand Canyon in Xizang, China. The discovery is based on three adult female frogs collected at Beibeng Township, Motuo County, Nyingchi City, in May 2025. The animals were named Megophrys (Viridophrys) motuoensis, and the authors also established a new subgenus, Viridophrys.

Their vivid green backs, reddish markings and distinctive combination of external features distinguish the Motuo population from other megophryine lineages. DNA analyses consistently recovered the three specimens as an independent lineage, although the exact relationship between that lineage and neighboring groups remains unresolved. The type locality lies at 2,750 metres above sea level in a region where the southern foothills of the Himalayas meet the lower Yarlung Tsangpo Grand Canyon.

Motuo County has recorded more than 40 amphibian species from 20 genera and six families, but the authors say extensive exploration has not exhausted its biological diversity. Improved road access enabled the May 2025 survey to reach areas that had previously been unexplored. The three toads were found at night between 01:40 and 02:50 on 11 May, perched on mossy substrates approximately one to three metres from a small stream less than one metre wide and dominated by large boulders.

The surrounding habitat was a mixed broadleaf and coniferous forest. The formal description combined field observations, measurements of preserved specimens, comparisons with published species accounts and molecular phylogenetic analyses. Megophryinae, the subfamily that contains the Asian horned toads, has 155 species and occurs across tropical and subtropical Asia, from northern India and southern China through the Sundas to the Philippines.

Its classification at the genus level remains disputed. Some studies divide the group into multiple genera, while others retain a broadly defined Megophrys containing several subgenera. The Motuo lineage was named at subgeneric and species level under the conservative framework of Mahony and colleagues because the available evidence did not establish a stable sister-group relationship or a single unmistakable external feature that would justify recognizing a separate genus.

For the molecular work, the researchers sequenced four mitochondrial genes—16S rDNA, 12S rDNA, cytochrome b and COI—and three nuclear genes—RAG-1, BDNF and RHOD. Existing sequences expanded the sample to 124 terminals representing 122 species: 119 ingroup species, two outgroups and the three newly sequenced specimens. Four datasets were subjected to maximum-likelihood and Bayesian analyses.

These comprised a 540-base-pair 16S matrix, a combined 4,529-base-pair mitochondrial and nuclear matrix, a 2,683-base-pair mitochondrial matrix and a 1,846-base-pair nuclear matrix. Nodes were considered well supported when Bayesian posterior probabilities were at least 0.95 and maximum-likelihood bootstrap values were at least 95%. The investigators also calculated minimum pairwise uncorrected 16S p-distances as supplementary information and used an exploratory principal component analysis to visualize morphometric variation.

Every molecular dataset recovered the three Motuo specimens as a distinct lineage, but the analyses did not agree on its closest relative. In the combined analysis, the new lineage, Brachytarsophrys and Atympanophrys formed a well-supported clade. Within that group, Atympanophrys was placed as sister to the clade containing the Motuo lineage and Brachytarsophrys, while the Motuo lineage was sister to Brachytarsophrys with a Bayesian posterior probability above 0.95.

The mitochondrial-only analysis also recovered the new lineage as sister to Brachytarsophrys, with maximum-likelihood bootstrap support above 95% and Bayesian posterior probability above 0.95. In contrast, the nuclear analysis gave only moderate support for the three-lineage cluster in the maximum-likelihood analysis, with a bootstrap value of 80%, and no support in the Bayesian analysis. The authors therefore treated the precise sister-group relationship as unresolved.

Genetic distances provided additional context but were not used alone to diagnose the taxon. Minimum pairwise uncorrected 16S p-distances between the Motuo lineage and representatives of other major megophryine lineages ranged from 6.13% to 13.82%. The smallest distance was to Atympanophrys, and the largest was to Grillitschia.

The distance to Brachytarsophrys was 6.83%. The 16S analysis itself did not strongly support the deeper node connecting the Motuo lineage to the other major lineages, underscoring the distinction between support for the sampled specimens as a monophyletic group and uncertainty about the group’s position within Megophryinae. The three adult females had snout–vent lengths of 46.5 to 48.6 millimetres, with a mean of 47.8 millimetres.

Mean head length was 16.7 millimetres and mean head width was 17.2 millimetres, consistent with the species’ broad head. The snout is obtusely rounded, without a rostral appendage, and the temporal region is short. The tympanum is large, rounded and fully exposed, while a broad, thick supratympanic fold curves over it and continues downward behind the tympanum.

Maxillary teeth are present, but vomerine teeth and vomerine ridges are absent. Rather than the prominent fleshy or horn-shaped eyelid structures found in many Asian horned toads, the Motuo frogs have minute tubercles along the outer edges of their upper eyelids. A combination of additional morphological characters helps separate Viridophrys from established subgeneric lineages.

The dorsal skin is rough and bears a vivid green ground colour, irregular vermilion mottling and scattered white spots. A reddish-brown triangle is present between the eyes. The throat and chest are light green or bluish green with irregular dark red or gray patterns, while the abdomen is pale grayish white to cream with irregular brown or reddish-brown markings.

A V-shaped parietoscapular ridge and an arcuate central dorsal ridge are present, but neither an occipital fold nor a dorsolateral fold occurs. Scattered white-tipped tubercles mark the flanks. The lower jaw is smooth, finger subarticular tubercles are absent, and the toes have neither webbing nor a lateral fringe.

These characters distinguish the Motuo frogs from Brachytarsophrys and Atympanophrys, which generally possess toe webbing and differ in eyelid and tympanum structure. The subgenus name Viridophrys combines the Latin viridis, meaning green, with the Greek ophrys, meaning eyebrow, referring to the animal’s extensive green dorsal markings. The species name motuoensis derives from Motuo County.

The proposed common names are the green horned toad subgenus and the Motuo green horned toad. In the exploratory principal component analysis, the first two components accounted for 88.2% and 9.3% of the total variation. The Motuo specimens formed a compact cluster separated from available Brachytarsophrys samples and closer to Atympanophrys along the first component.

Because the analysis included only three newly examined individuals and literature-derived measurements collected under potentially different protocols, the researchers used it only as a supplementary visualization rather than as primary evidence for diagnosing the new taxon. Current knowledge of the species is limited to its type locality and the three collected females. Their well-developed, convoluted oviducts and ovaries containing immature oocytes indicated sexual maturity, but no males, calls, amplexus or mature eggs were observed.

The breeding season therefore remains unknown. The site was revisited on 2 June, 28 June and 27 August 2025, but no additional animals were found, and no males were detected during subsequent surveys. The species’ population size, geographic range and trend are likewise unknown.

The authors describe Megophrys (Viridophrys) motuoensis as the only known megophryid with a vivid green dorsum, a coloration that may provide camouflage among mossy streamside substrates. Its known habitat is at approximately 2,750 metres, and the authors note that a high-elevation specialist could face threats as warming progressively compresses its suitable climatic niche. The type locality lies within the Xizang Yarlung Tsangpo Grand Canyon National Nature Reserve, which may provide some legal protection.

They caution, however, that protected status does not remove pressures including tourism and habitat disturbance associated with improved road access. Field surveys and taxonomic studies are needed to document the species’ full distribution, population size and trends before a formal conservation assessment can be made. The discovery shows that substantial unresolved amphibian diversity persists even within a country that has one of the world’s richest amphibian faunas.

The Motuo population is genetically distinguishable and morphologically diagnosable, but its closest relative remains uncertain, supporting recognition as a distinct subgenus rather than a separate genus. Its discovery also illustrates the limits of current sampling in the remote mountain landscape of eastern Himalayas. Until males, additional populations and further habitat records are found, the Motuo green horned toad is known only from three adult females collected beside one high-elevation stream, leaving its range, breeding ecology and conservation status unresolved.

Subject of Research: Description of a new subgenus and species of Asian horned toad from Motuo County, Xizang, China

Article Title: A striking new subgenus and species of Asian horned toads ( Anura , Megophryidae , Megophryinae ) from Xizang, China

Article References: Liu, X.-L., Zhang, Y.-P., Wei, P.-F., Ai, R.-D., Lu, W.-Z., Li, X.-Q., Zhou, W.-W., Chen, J.-M., & Yuan, Z.-Y. (2026). A striking new subgenus and species of Asian horned toads (Anura, Megophryidae, Megophryinae) from Xizang, China. Zoosystematics and Evolution, 102(5), 1295-1313. https://doi.org/10.3897/zse.102.183945

Image Credits: AI Generated

DOI: 10.3897/zse.102.183945

Keywords: Megophrys motuoensis, Viridophrys, Asian horned toads, Megophryinae, amphibian discovery, Xizang, Yarlung Tsangpo Grand Canyon, molecular phylogeny, taxonomy, biodiversity, striking, subgenus