An unexpected discovery of hidden diversity: a new species of the genus Calamaria H. Boie in F. Boie, 1827 (Squamata, Calamariidae) from Guangxi, China

As part of our investigations into the systematics of the Calamaria pavimentata species complex, we describe a new species of the genus Calamaria from Chongzuo and Guilin Cities, Guangxi, China, based on a combination of morphological and molecular evidence. Morphologically, Calamaria incredibilis sp. nov. is distinguished from other congeners by the following combination of morphological characters: nine enlarged maxillary teeth; rostral higher than wide; prefrontal shorter than frontal and contacting the first two supralabials; mental not in contact with anterior chin shields; dorsal scales in 13–13 – 13 rows, smooth throughout; a single preocular and postocular; four supralabials, with the 2 nd and 3 rd ones contacting the eye; five infralabials; six scales surrounding the paraparietal; 170–182 ventrals in males; 21–23 paired subcaudals in males; a relatively short tail (8.2–8.4 % of total length in males), thick and nearly cylindrical, gradually tapering to an obtuse point; dorsal coloration brown, seven longitudinal series of interrupted dark brown stripes are visible along the body, extending from behind the pale-colored collar to the tip of the tail; the margins of the dorsal scales are heavily suffused with black pigment, forming an almost reticulate pattern; the ventral surface yellowish white, with dark brown blotches along the outermost lateral margins; the absence of light spots on the dorsal tail.

Phylogenetic analyses based on mitochondrial cytochrome b sequences recover Calamaria incredibilis sp. nov. as a well-supported independent lineage, forming a sister relationship with a subclade comprising C. andersoni Yang & Zheng, C. synergis Zhang, Xu, Nguyen, Poyarkov, Vogel, Wang & Huang, and C. yunnanensis Chernov. The new species is separated from its closest relatives by substantial mitochondrial genetic divergence (p - distance 12.67 % based on cytochrome b gene).

The discovery of Calamaria incredibilis sp. nov. further highlights the underestimated diversity within the C. pavimentata species complex and underscores the importance of integrative taxonomic approaches for resolving cryptic diversity in morphologically conservative, semi-fossorial snake lineages from southern China, with Guangxi emerging as an important hotspot of cryptic diversification.