“…4 Cryptobranchoidea is the most primitive clade of the crown group salamanders (Urodela) and contains two subclades: Pancryptobrancha (crown + stem cryptobranchids; Vasilyan et al, 2013) and Panhynobia (crown + stem hynobiids; Jia et al, 2021a). The two subclades are united by a set of synapomorphies as sister-group taxa (Dunn, 1922;Estes, 1981;Jia et al, 2021a), but are different from each other in life history strategies and ecological preferences at their respective adult stage: most pancryptobranchans are neotenic or partially metamorphosed and live in water permanently by retaining larval features (e.g., gill slits), albeit the pancryptobranchan Aviturus from the Paleocene was interpreted as semiaquatic with an unknown life history strategy (Vasilyan and Böhme, 2012). Alternatively, panhynobians are predominantly metamorphosed, except that the stem hynobiid Regalerpeton from Early Cretaceous (Rong, 2018) and some populations of the living hynobiid Batrachuperus londongensis are neotenic (Jiang et al, 2018).…”