The Varanidae were defined (using morphological characteristics) by Estes,de Queiroz andGauthier (1988) as the clade containing the most recent common ancestor ofLanthanotus andVaranus and all of its descendants.[4] A similar definition was formulated by Conradet al. (2008) (also using morphological data), who defined the Varanidae as the clade containingVaranus 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.
Lee (1997) created a different definition of the Varanidae, defining them as the clade containingVaranus and all taxa more closely related toVaranus than toLanthanotus;[6][7] this definition explicitly excludes theearless monitor lizard from the Varanidae. WhetherL. borneensis is included in or excluded from the Varanidae depends on the author; for example, Vidalet al. (2012) classify the earless monitor lizard as a member of a separate familyLanthanotidae,[8] while Gauthieret al. (2012) classify it as a member of Varanidae.[9]
Monitor lizards are reputed to be among the most intelligent lizards. Most speciesforage widely and have large home ranges,[11] and many have high stamina.[12] Although most species are carnivorous, threearboreal species in thePhilippines (Varanus olivaceus,Varanus mabitang, andVaranus bitatawa) are primarily frugivores.[1][13] Among species of living varanids, the limbs show positiveallometry, being larger in larger-bodied species, although the feet become smaller as compared with the lengths of the other limb segments.[14]
Varanids possess unidirectional pulmonary airflow, includingair-sacs akin to those of birds.[15]
^de Queiroz K, Gauthier J (1988). "Phylogenetic Relationships within Squamata". In Estes RJ, Pregill GK (eds.).Phylogenetic Relationships of the Lizard Families: Essays Commemorating Charles L. Camp. Stanford University Press. p. 166.ISBN9780804714358.OCLC16646258.
^Conrad J (2008). "Phylogeny and systematics of Squamata (Reptilia) based on morphology".Bulletin of the American Museum of Natural History.310:1–182.doi:10.1206/310.1.hdl:2246/5915.S2CID85271610.
^Gauthier JA, Kearney M, Maisano JA, Rieppel O, Behlke AD (2012). "Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record".Bulletin of the Peabody Museum of Natural History.53 (1):3–308.doi:10.3374/014.053.0101.S2CID86355757.
^Greene HW (1986).Diet and Arboreality in the Emerald Monitor, Varanus prasinus, with Comments on the Study of Adaptation. Chicago: Field Museum of Natural History.OCLC14915452.OL7155983M.
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