There are two
infraorders of living snakes:
Alethinophidia and
Scolecophidia. This separation is based primarily on
morphological characteristics between family groups; however, more recently, the comparison of
mitochondrial DNA has played its part. As with most taxonomic classifications, there are many different interpretations of the evolutionary relationships. This had resulted in families being moved to different infraorders, the merging or splitting of infraorders and families. For instance, many sources classify
Boidae and
Pythonidae as the same family, or keep others, such as
Elapidae and
Hydrophiidae, separate for practical reasons despite their extremely close relationship. ==See also==