A taxonomic revision of Cynanchumthesioides (Apocynaceae) with two new synonyms.

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