Varanopidae - Taxonomy and Phylogeny

Taxonomy and Phylogeny

Class Synapsida

• Family Varanopidae
  • Apsisaurus
  • Archaeovenator
  • Basicranodon (possible junior synonym of Mycterosaurus)
  • Pyozia
  • ? Thrausmosaurus (nomen dubium)
  • Varanosaurus
  • Subfamily Mycterosaurinae
    • Heleosaurus
    • Mesenosaurus
    • Mycterosaurus
  • Subfamily Varanodontinae
    • Aerosaurus
    • ? Elliotsmithia
    • Ruthiromia
    • Varanodon
    • Varanops
    • Watongia

Apsisaurus was formerly assigned as a "eosuchian" diapsid. In 2010, it was redescribed by Robert R. Reisz, Michel Laurin and David Marjanovic and classified as a basal varanopid synapsid. The cladogram below is modified after Reisz, Laurin and Marjanovic, 2010.

Both Basicranodon and Ruthiromia were tentatively assigned to Varanopidae by Reisz (1986), but have been neglected in more recent studies. They were included for the first time in a phylogenetic analysis by Benson (in press). Ruthiromia was found to be most closely related to Aerosaurus. Basicranodon was found to be a wildcard taxon due to its small amount of known materials, as it is based on a partial braincase from the ?Kungurian stage Richards Spur locality in Oklahoma. It occupies two possible positions, falling either as a Mycterosaurinae, or as the sister taxon of Pyozia. Although Reisz et al. (1997) considered Basicranodon as a subjective junior synonym of Mycterosaurus, Benson (in press) found some differences in the distribution of teeth and shape of the dentigerous ventral platform medial to the basipterygoid processes that may indicate taxonomic distinction. Below is a cladogram modified from the analysis of Benson (in press), after the exlusion of Basicranodon: