Varanids | |
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Male Komodo dragons ( Varanus komodoensis) fighting, Indonesia | |
Fossil of Saniwa , an extinct varanid known from the Eocene of North America | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Squamata |
Superfamily: | Varanoidea |
Family: | Varanidae Merrem, 1820 |
Genera | |
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The Varanidae are a family of lizards in the superfamily Varanoidea and order Anguimorpha. The family, a group of carnivorous and frugivorous lizards, [1] includes the living genus Varanus and a number of extinct genera more closely related to Varanus than to the earless monitor lizard (Lanthanotus). [2] 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 earless monitor lizard and Chinese crocodile lizard. [3] The oldest members of the family are known from the Late Cretaceous of Mongolia. [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.
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; [6] [7] 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, [8] while Gauthier et al. (2012) classify it as a member of Varanidae. [9]
Genera included in Varanidae according to Dong et al., 2022 [2]
Monitor lizards are reputed to be among the most intelligent lizards. Most species forage widely and have large home ranges, [11] and many have high stamina. [12] Although most species are carnivorous, three arboreal species in the Philippines ( Varanus olivaceus , Varanus mabitang , and Varanus bitatawa ) are primarily frugivores. [1] [13] 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. [14]
Varanids possess unidirectional pulmonary airflow, including air-sacs akin to those of birds. [15]
The earless monitor lizard is a semiaquatic, brown lizard native to the Southeast Asian island of Borneo. It is the only living species in the family Lanthanotidae and it is related to the true monitor lizards.
Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recognized.
Heloderma is a genus of toxicoferan lizards that contains five species, all of which are venomous. It is the only extant genus of the family Helodermatidae.
Megalania is an extinct species of giant monitor lizard, part of the megafaunal assemblage that inhabited Australia during the Pleistocene. It is the largest terrestrial lizard known to have existed, but the fragmentary nature of known remains make estimates highly uncertain. Recent studies suggest that most known specimens would have reached around 2–3 m (6.6–9.8 ft) in body length excluding the tail, while some individuals would have been significantly larger.
Toxicofera is a proposed clade of scaled reptiles (squamates) that includes the Serpentes (snakes), Anguimorpha and Iguania. Toxicofera contains about 4,600 species, of extant Squamata. It encompasses all venomous reptile species, as well as numerous related non-venomous species. There is little morphological evidence to support this grouping; however, it has been recovered by all molecular analyses as of 2012.
The emerald tree monitor or green tree monitor, is a small to medium-sized arboreal monitor lizard. It is known for its unusual coloration, which consists of shades from green to turquoise, topped with dark, transversedorsal banding. This coloration helps camouflage it in its arboreal habitat. Its color also makes the emerald tree monitor highly prized in both the pet trade and zoos alike.
Palaeosaniwa canadensis is an extinct species of carnivorous lizard from the late Cretaceous of North America. The name, given by Charles Whitney Gilmore in 1928, means "ancient Saniwa from Canada".
Varanoidea is a superfamily of lizards, including the well-known family Varanidae. Also included in the Varanoidea are the Lanthanotidae, and the extinct Palaeovaranidae.
The Anguimorpha is a suborder of squamates. The group was named by Fürbringer in 1900 to include all autarchoglossans closer to Varanus and Anguis than Scincus. These lizards, along with iguanians and snakes, constitute the proposed "venom clade" Toxicofera of all venomous reptiles.
Platynota is a polyphyletic group of anguimorph lizards and thus belongs to the order Squamata of the class Reptilia. Since it was named in 1839, it has included several groups, including monitor lizards, snakes, mosasaurs, and helodermatids. Its taxonomic use still varies, as it is sometimes considered equivalent to the group Varanoidea and other times viewed as a distinct group. It is phylogenetically defined as a clade containing Varanidae. It also includes many extinct species.
Susan Elizabeth Evans is a British palaeontologist and herpetologist. She is the author or co-author of over 100 peer-reviewed papers and book chapters.
Aiolosaurus is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, Aiolosaurus oriens, was named in 2000 from Ukhaa Tolgod, a rich fossil site in the Campanian-age Djadochta Formation.
Telmasaurus is an extinct genus of varanoid lizard from the Late Cretaceous of Mongolia. Fossils have been found from the Djadokha and Barun Goyot Formations that date between the early and middle Campanian stage from approximately 80 to 75 million years ago. The type species Telmasaurus grangeri was named in 1943.
Proplatynotia is an extinct genus of varanoid lizard from the Late Cretaceous of Mongolia. Fossils have been found in the Barun Goyot Formation, which is mid-Campanian in age. The type and only species, P. longirostrata, was named in 1984.
Saniwa is an extinct genus of varanid lizard that lived during the Eocene epoch. It is known from well-preserved fossils found in the Bridger and Green River Formations of Wyoming, United States. The type species S. ensidens was described in 1870 as the first fossil lizard known from North America. A second species, S.orsmaelensis, is recognised from remains found in Europe. It is a close relative of Varanus, the genus that includes monitor lizards.
Priscagamidae is an extinct family of iguanian lizards known from the Late Cretaceous of Mongolia and China and the Eocene of India, spanning a range from 83.6 to 48.6 million years ago. Probably the earliest priscagamids on indeterminate genera were found in Aptian-Albian sediments in "Hobur", Mongolia. It includes the genera Heterodontagama, Mimeosaurus, Phrynosomimus, Priscagama, and possibly Pleurodontagama. The first fossils of priscagamids were found in the Djadochta and Khermeen Tsav formations of Mongolia. More recently they have been found in the Cambay Formation in India, leading to the naming of Heterodontagama in 2013. Priscagamidae was originally described as a subfamily of Agamidae called Priscagaminae in 1984, but it was reclassified as a distinct family in 1989. Most phylogenetic analyses still find a close relationship between Priscagamidae and Agamidae, although a 2015 study found it to be basal to all other iguanian clades, warranting its removal from Iguania and placement in a larger clade called Iguanomorpha.
Paleoanguimorpha is a clade of anguimorphs comprising Shinisauria and Goannasauria. Morphological studies in the past also classified helodermatids and pythonomorphs with the varanoids in the clade Platynota, while the Chinese crocodile lizard was classified as a xenosaurid. Current molecular work finds no support in these groupings and instead has found the helodermatids more related to Diploglossa in the sister clade Neoanguimorpha, while the Chinese crocodile lizard is the closet living relative to varanoids. Pythonomorphs represented by snakes today are not closely related to varanoids and are instead a sister lineage to Anguimorpha and Iguania in the clade Toxicofera.
Archaeovaranus is genus of varanid lizard from the early Eocene (Ypresian) Yuhuangding Formation of Hubei Province, China. The genus contains a single species, Archaeovaranus lii, known from a nearly complete skeleton. The holotype, which includes an intact skull, is associated but disarticulated. Archaeovaranus fills a gap in the varanid fossil record, as it represents a stem-varanid from the early Eocene of East Asia, and is the closest known relative of Varanus.
Varanus tsukamotoi, the Mariana monitor or Saipan monitor, is a species of lizard of the Varanidae family. It is endemic to the Northern Mariana Islands and Guam, and has been introduced to Japtan in the Marshall Islands.
Varanus hooijeri is an extinct species of medium-sized monitor lizard found in Liang Bua on Flores and possibly also Sumba, dating to the Late Pleistocene and Holocene.