[2] The Varanidae were defined (using morphological characteristics) by Estes, de Queiroz and Gauthier (1988) as the clade containing the most recent common ancestor of Lanthanotus and Varanus and all of its descendants.

[4] A similar definition was formulated by Conrad et al. (2008) (also using morphological data), who defined the Varanidae as the clade containing Varanus varius, Lanthanotus borneensis, and all descendants of their last common ancestor.

[5] Using one of these definitions leads to the inclusion of the earless monitor lizard (L. borneensis) in the family Varanidae.

Whether L. borneensis is included in or excluded from the Varanidae depends on the author; for example, Vidal et al. (2012) classify the earless monitor lizard as a member of a separate family Lanthanotidae,[8] while Gauthier et al. (2012) classify it as a member of Varanidae.

[14] Varanids possess unidirectional pulmonary airflow, including air-sacs akin to those of birds.