Varanidae
The Varanidae are a family of lizards in the superfamily Varanoidea within the Anguimorpha group. The family, a group of carnivorous and frugivorous lizards, includes the living genus "Varanus" and a number of extinct genera. "Varanus" includes the Komodo dragon (the largest living lizard), crocodile monitor, savannah monitor, the goannas of Australia and Southeast Asia, and various other species with a similarly distinctive appearance. Their closest living relatives are the anguid and helodermatid lizards. Taxonomy. 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. 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. Using one of these definitions leads to the inclusion of the earless monitor lizard ("L. borneensis") in the family Varanidae. Lee (1997) created a different definition of the Varanidae, defining them as the clade containing "Varanus" and all taxa more closely related to "Varanus" than to "Lanthanotus"; this definition explicitly excludes the earless monitor lizard from the 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, while Gauthier "et al." (2012) classify it as a member of Varanidae. Taxonomic analysis based on molecular data has identified that "Varanus" and "Lanthanotus" make up Varanidae, while Shinisaurus is a sister taxon. Genera. Genera usually included in Varanidae (under subfamily Varaninae according to Conrad "et al.", 2008)): Genera sometimes included in the Varanidae (under subfamily Lanthanotinae according to Conrad "et al.", 2008), treated as under  the separate family Lanthanotidae by other authors: Basal varanoids: Formerly included in the Varanidae: Phylogeny. Below is a cladogram from Conrad "et al." (2008) that shows relationships within Varanoidea: Biology. Monitor lizards are reputed to be among the most intelligent lizards. Most species forage widely and have large home ranges, and many have high stamina. Although most species are carnivorous, three arboreal species in the Philippines ("Varanus olivaceus", "Varanus mabitang", and "Varanus bitatawa") are primarily frugivores. Among species of living varanids, the limbs show positive allometry, being larger in larger-bodied species, although the feet become smaller as compared with  the lengths of the other limb segments. Varanids possess unidirectional pulmonary airflow, including airsacs akin to those of birds.