Two new onychiurid species, Thalassaphorura microspinata sp. nov. and T. guangxiensis sp. nov., are reported from the karsts of south China (Guangxi). T. microspinata sp. nov. is similar to T. grandis Sun, Chen & Deharveng, 2010 in having the same dorsal and ventral pso formula, number of pseudocelli on subcoxae 1, number of chaetae in the distal whorl of tibiotarsi and number of p-chaetae between inner posterior pso on head; but it can be recognized by the smaller body size, shorter AS, 5 chaetae on baso-lateral part of labium, distinguishable S-chaetae and absence of chaetae on Th. I sternum. T. guangxiensis sp. nov. possesses the same dorsal pso formula as Chinese species T. reducta Sun, Chen & Deharveng, 2010, T. bapen Sun, Chen & Deharveng, 2010 and T. guangdongensis Sun & Li, 2015a, but they could be separated easily by ventral pso formula, number of pseudocelli on subcoxae 1 and other combined characters. An updated key of world species of the genus Thalassaphorura is provided. The species Thalassaphorura saccardyi (Denis, 1935) is transferred to the genus Protaphorura Absolon, 1901 on examination of the type material. In addition to those listed in Sun et al. (2010), two additional species placed in Thalassaphorura by Parimuchová & Kováč 2016 are considered here as incertae sedis because of insufficient descriptions: Thalassaphorura boskovae (Lučić, Dimitrijević & Mihajlova, 2003), and T. tamdaona (Nguyen, 1995).
Keywords: Collembola, systematics, Thalassaphorura microspinata sp. nov., Thalassaphorura guangxiensis sp. nov., Guangxi.