Morphological and molecular evidence reveal a new species of the genus Paramesotriton (Caudata, Salamandridae) from Chongqing, China

Based on morphological and molecular phylogenetic evidence, this study describes a new species of the salamandrid genus Paramesotriton discovered in Pengshui Miao and Tujia Autonomous County, Chongqing Municipality, China. The taxonomic status of this new species was established through integrated morphological characterization and multi-gene phylogenetic analysis (mitochondrial genes ND 2 and Cytb, and nuclear gene POMC).

The new species is primarily diagnosed by the following characteristics: presence of horn-like projections posterior to the head; black ground coloration on the throat and venter adorned with irregular orange-red blotches; bluntly rounded tail tip; and overlapping digits when the limbs are pressed along the body flank with the forelimb backward and the hind limb forward. Additional diagnostic characteristics include the absence of vestigial gills and gill filaments and lack of yellow spots on lateral sides of dorsum and tail.

Molecular phylogenetic analyses place the new species within the P. caudopunctatus group (Clade B), forming a strongly supported sister group (BI = 0.91, ML = 74) to the combined clade comprising P. maolanensis, P. wumengshanensis and P. longliensis. The minimum genetic distance between the new species and its closest relative P. maolanensis reaches 0.78 % (Cytb, p-distances), exceeding interspecific divergence observed among some congeners (e. g., 0.63 % between P. maolanensis and P. longliensis), further supporting its distinct species status.

This discovery further validates the persistence of cryptic diversity in the karst mountain regions of southwestern China, such as the Wuling Mountains. The new species has a restricted distribution and specialization to stream habitats at elevations of 700–1000 meters which render it is highly susceptible to threats from habitat fragmentation and illegal exploitation. It is recommended that this species should be categorized as “ threatened ” and that urgent conservation measures need to be implemented.