摘要The Tien's Mountain Stream Snake,Opisthotropis daovantieni Orlov,Darevsky,and Murphy,1998,has been represented solely by its type series,with no additional specimens reported in the past two decades.As a result,limited data exist and O.daovantieni remains one of the least studied members of its genus.Based on a re-examination of the type series,analysis of newly collected topotypic specimens,and a review of museum collections,this study provides an updated and comprehensive morphological characterization of O.daovantieni including detailed descriptions of hemipenial morphology,revised diagnostic characters,phylogenetic positioning,and ecological insights.Based on morphological comparisons with congeners,we also define the informal Opisthotropis spenceri group to facilitate future taxonomic work.In addition,this study documents a previously unreported defensive behavior involving tail-poking,observed in the field and thus far unique within the genus Opisthotropis.