A new species of Diploderma Hallowell, 1861 (Squamata, Agamidae) discovered in the upper Dadu River valley of the Hengduan Mountains, Sichuan, China

A new species of the genus Diploderma is described from the upper Dadu River Valley in the Hengduan mountains of Sichuan Province, China. Phylogenetic analyses based on the mitochondrial ND2 gene revealed that the new species, Diploderma bifluviale sp. nov. , forms a distinct lineage within the Diploderma flaviceps group with an uncorrected genetic distance of ≥3.88%. Morphologically, the new species differs from its congeners by a combination of characters, including a shorter snout-vent length (SVL 62.51–72.55 mm), a shorter tail (TAL/SVL ratio 1.37–1.56), concealed tympanum, absence of a gular spot, and lemon-chiffon dorsolateral stripes with serrated edges in males. Additionally, Diploderma bifluviale sp. nov. exhibits unique coloration traits such as a wheat-colored tongue and the fourth toe with claw reaching either the tympanum or the area between shoulder and tympanum when hind limbs adpressed forward. The species inhabits semi-arid shrublands in warm-dry valleys at elevations of 2,187–2,525 m – a habitat that is distinct from those of its closest relatives. This discovery highlights the understudied biodiversity of the upper Dadu River. Diploderma bifluviale sp. nov. represents the 49 th species of the genus and expands our understanding of morphological and ecological diversity within the D. flaviceps group.