 The Cryptobranchoidea ( primitive salamanders ) and the Salamandroidea , also known as Diadectosalamandroidei , ( advanced salamanders ) are believed to be sister groups . Both seem to have appeared before the end of the Jurassic , the former being exemplified by Chunerpeton tianyiensis , Pangerpeton sinensis , Jeholotriton paradoxus , Regalerpeton weichangensis , Liaoxitriton daohugouensis and Iridotriton hechti , and the latter by Beiyanerpeton jianpingensis . By the Upper Cretaceous , most or all of the living salamander families had probably appeared . 
