Considered to be closely related to Emydoidea by McDowell (1964) and Dryden (1985) based on skeletal morphology, but not by Frair (1982c) or Seidel and Adkins (1989) based on serology and myoglobins, respectively, or by Bramble (1974) or Gaffney and Meylan (1988) based on morphology.