A New Species of Herpetoreas from Southern Xizang, China, with Comments on the Systematic Position of H. sieboldii (Serpentes: Natricidae)

The natricid snake genus Herpetoreas Günther, 1860, is predominantly distributed throughout the southern Himalayan region. Over the past decade, intensive field investigations and taxonomic studies have led to the successful discovery and description of four cryptic species within this group. Nevertheless, data suggest that species diversity remains significantly underestimated and that the systematic position of certain members still requires clarification. Five new specimens initially identified as Herpetoreas were collected during field work on the Qinghai-Xizang Plateau. Comprehensive molecular phylogenetic analyses and morphological comparisons confirmed that two specimens represented a cryptic species, while the remaining three were identified as the rare H. sieboldii Günther, 1860. In addition to the significant genetic divergence, the new species exhibits diagnostic morphological characteristics that distinguish it from its congeners : (1) preoculars 2; (2) postoculars 2; (3) temporals 1+2 or 1+1+2; (4) dorsal scale rows 19-19-17, all keeled except the outer one, dorsal scale reduction from 19 to 17 rows at 109th -111th VS; (5) ventrals 215-219; (6) cloacal plate divided; (7) subcaudals 89-90, paired; (8) the reduction of tail dorsal scales from 8 to 6 rows occurs at position 35-36 SC, and 6 to 4 at 74 SC; (9) tail segments with 4 supracaudal scale rows constitutes 0.38%-0.42% of those with 6 rows; (10) a wide dark stripe extending from the posterior eye to the upper corner of the mouth; (11) dorsum brick-brown in live, speckled with short dark stripes; (12) body and tail venter immaculate, each shield decorated with dark spots on the lateral edges. The systematics of H. sieboldii and H. platyceps are also discussed based on molecular data