Disagreement exists between different authorities as to the definition of the terms Caudata and Urodela. Some maintain that the Urodela should be restricted to the crown group, with the Caudata being used for the total group. Others restrict the name Caudata to the crown group and use Urodela for the total group.[66][67] The former approach seems to be most widely adopted and is used in this article.[46]
The 10 families belonging to the Urodela are divided into three suborders.[66] The clade Neocaudata is often used to separate the Cryptobranchoidea and Salamandroidea from the Sirenoidea.