A taxonomic revision of Cynanchum thesioides (Apocynaceae) with two new synonyms

Cynanchum thesioides, a species widely distributed in north-eastern Asia, is revised to include two new synonyms: Vincetoxicum sibiricum f. linearifolium, described from Shandong, China in 1877, but long neglected and Cynanchum gobicum, previously believed to be endemic to Mongolia. Typification for C. thesioides and all its synonyms is given, including lectotypification of V. sibiricum var. australe and V. sibiricum f. linearifolium. An updated description, three figures showing the diverse habitats, habits and variation in morphological characters, and a general distribution map are also provided