Acanthosaura syrax sp. nov., a new species of mountain horned dragon from high-elevation habitats of western Thailand (Squamata, Agamidae)

A new species of mountain horned dragon, Acanthosaura syrax sp. nov ., is described from the high–elevation evergreen forests of Mae Wong National Park in western Thailand. Morphological comparisons distinguish the new taxon from its congeners by its smaller body size and the fact that it possesses the smallest nuchal and dorsal scales recorded within the genus. Phylogenetic analysis of mitochondrial ND2 and COI gene sequences further supports this distinction, identifying the new species as a reciprocal monophyletic lineage with 76% and 99% nodal support in maximum–likelihood analyses and 0.78 and 1.00 nodal support in Bayesian Inference analyses based on ND2 and COI genes, respectively. Interspecific pairwise genetic distances between A. syrax sp. nov . and other congeners range from 14.1–15.9% in ND2 gene and 14.96–28.13% in COI gene, while intraspecific variation remains low at 0–0.01% and 0–0.34% in ND2 and COI, respectively. This discovery brings the number of Acanthosaura species to 23 and highlights the significant and unique biodiversity found within the high–altitude evergreen ecosystems of western Thailand.