Varanus (Odatria) | |
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Spiny-tailed monitor at the Cincinnati Zoo | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Squamata |
Family: | Varanidae |
Genus: | Varanus |
Subgenus: | Odatria Gray, 1838 |
Type species | |
Varanus tristis Schlegel, 1839 | |
Species | |
Odatria, commonly known as dwarf monitors, [1] consists of small monitor lizards found in Australia and Indonesia. Species in this subgenus include the smallest monitor species in the world, the tiny 16 gram Dampier Peninsula monitor, but also includes some more medium sized species such as the 240 gram black-palmed rock monitor. [2]
Odatria was coined by John Edward Gray in 1838, albeit as a genus name.
Odatria is the most species diverse subgenus of monitor lizards, with 22 different species. The subgenus also includes two species complexes represented by the spiny-tailed monitor and the Timor monitor. Alternatively, Vidal et al. 2012 splits Odatria into two species groups represented by the spiny-tailed monitor and the black-headed monitor.
In the past, tree monitors such as the green tree monitor have sometimes been included within Odatria as well as Euprepriosaurus, but now form their own subgenus Hapturosaurus .
A 2020 phylogenomic study by Brennan et al. found that Odatria is most closely related to much larger Australian monitor lizards from the subgenus Varanus, which includes the largest living lizard, the Komodo dragon, as well as the monotypic subgenus Papusaurus of which the crocodile monitor is the only member of. Together, Odatria, Varanus, and Papusaurus form a monophyletic clade of Indo-Australopapuan monitors. [3]
The same study found the black-palmed rock monitor, the largest species within Odatria, as sister to the rest of Odatria, making it the most basal species within the subgenus. [3] Vidal et al. 2012 also recovers this species as the most basal, although within the V. tristis group. [4]
During the early-mid Oligocene, the genus Varanus dispersed in two directions. The southeastern dispersion into Indo-Australia likely occurred shortly after the collision of the Asian and Australian tectonic plates, which created a connection between Sahul and Sundaland, i.e., an Indonesian land bridge that would have facilitated the dispersal of monitor lizards into Australia. The existence of this land bridge also likely allowed the Indo-Australopapuan clade including many Odatria species to disperse back into Indonesia. [3] True monitors (subgenus Varanus ) and Papuan monitors (subgenus Papusaurus ) form a clade that is considered the sister taxon of Odatria. [5]
Vidal et al. 2012 separated Odatria into two species groups; the V. acanthurus group included V. acanthurus, V. baritji, V. brevicauda, V. bushi, V. caudolineatus, V. eremius, V. gilleni, V. kingorum, V. primordius, and V. storri, while the V. tristis group included V. auffenbergi, V. glauerti, V. glebopalma, V. mitchelli, V. pilbarensis, V. scalaris, V. semiremex, V. similis, V. timorensis, and V. tristis. [4]
To maintain monophyly in light of Brennan et al. 2020, V. glebopalma would be excluded from the V. tristis group, and more species would be included as in the following:
V. acanthurus group - (V. acanthurus, V. baritji, V. brevicauda, V. bushi, V. caudolineatus, V. eremius, V. gilleni, V. kingorum, V. primordius, V. sparnus and V. storri)
V. tristis group - (V. auffenbergi, V. glauerti, V. hamersleyensis, V. mitchelli, V. pilbarensis, V. scalaris, V. semiremex, V. similis, V. timorensis, and V. tristis)
Brennan et al. 2020 | Vidal et al. 2012 |
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The genus is diverse in terms of behaviour, and includes terrestrial, arboreal, and semiaquatic species. Many are saxicolous, i.e., they are strongly associated with rocky habitats, while some others prefer forests. [2]
Ritualized fighting sometimes occurs between males. Unlike many larger monitors which grapple with each other while standing on their hind legs, some dwarf monitor species instead grapple each other with all 4 limbs, belly to belly, and roll around on the ground trying to force the other onto its back. Biting may also occur. [6]
Orthopteran insects and other species of lizards make up the mainstay of the diet for most species. One species, the rusty desert monitor, consumes a particularly large amount of lizard prey with lizards such as various species of Ctenotus accounting for up to 70% of their diet by weight. [7] Larger species such as black-palmed rock monitors are also known to prey on other dwarf monitors. [2]
Like all other monitors, all species within Odatria are oviparous. As parthenogenesis is well known in monitor lizards in some other subgenera, it is possible that dwarf monitors are also capable of parthenogenesis; there is a report of a suspected case of parthenogenesis in peacock monitors. [2]
Physalopterid nematodes of the genus Abbreviata are major gastrointestinal parasites in many species of reptiles. Those that parasitize dwarf monitors include A. hastaspicula and A. levicauda ; the former may specialize in Australian monitors. Depending on the species, more than half of all individuals collected from the wild may be infected, but in most cases the parasites do minimal harm. Various other parasites are also known, but in comparatively much low numbers. [1] [8] In captivity, wild caught individuals may suffer more from the effects of parasites due to the stressful process of being taken from the wild and being shipped elsewhere.
Under the EPBC Act, the export of live Australian Odatria species for commercial purposes is prohibited. Illegal trade of these species still persist, as many dwarf monitor species are in great demand in the pet trade. In Australia, monitor lizards are threatened by the invasive cane toad, as they have no natural immunity to the toad's toxins when ingested. [2]
Captive breeding for the pet trade has been successful in many such species however and lessens the pressure on wild populations. Some such as the often captive bred ridge-tailed monitor are popular pet lizards, in some cases as a "beginner monitor" to train those who are aspiring to eventually keep larger and less forgiving monitor lizard species.
Species | Taxon author | Common name | Picture |
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V. glebopalma | Mitchell, 1955 | black-palmed rock monitor |
Species | Taxon author | Common name | Picture |
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V. acanthurus | Boulenger, 1885 | ackie monitor, Ackie's dwarf monitor, Australian spiny-tailed monitor, ridge-tailed monitor, spiny-tailed monitor | ![]() |
V. baritji | M. King & Horner, 1987 | black-spotted ridge-tailed monitor, black-spotted spiny-tailed monitor, lemon-throated monitor, northern ridge-tailed monitor, White's dwarf goanna, White's dwarf monitor, Whites monitor, yellow-throated monitor | |
V. brevicauda | Boulenger, 1898 | short-tailed monitor, short-tailed pygmy monitor | |
V. bushi | Aplin, Fitch & D.J. King, 2006 | Bush's monitor, Bush's pygmy monitor, Pilbara monitor, Pilbara mulga monitor, Pilbara stripe-tailed monitor | |
V. caudolineatus | Boulenger, 1885 | line-tailed pygmy monitor, stripe-tailed goanna, stripe-tailed monitor | ![]() |
V. citrinus | Pavón-Vázquez, Esquerré, Fitch, Maryan, Doughty, Donnellan & Keogh, 2022 | Gulf ridge-tailed monitor | |
V. eremius | Lucas & Frost, 1895 | pygmy desert monitor, rusty desert monitor | |
V. gilleni | Lucas & Frost, 1895 | Gillen's monitor, mulga monitor, pygmy mulga monitor | |
V. insulanicus | Mertens, 1958 | Groote Eylandt monitor | |
V. kingorum | Storr, 1980 | Kings' goanna, Kings' monitor, Kings' rock monitor, pygmy rock monitor | |
V. ocreatus | Storr, 1980 | Storr's monitor, western Storr's monitor | |
V. primordius | Mertens, 1942 | northern blunt-spined monitor, northern ridge-tailed monitor | |
V. sparnus | Doughty, Keally, Fitch & Donnellan, 2014 | Dampier peninsula goanna, Dampier Peninsula monitor | |
V. storri | Mertens, 1966 | Storr's monitor | ![]() |
Species | Taxon author | Common name | Picture |
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V. auffenbergi | Sprackland, 1999 | Auffenberg's monitot, peacock monitor | ![]() |
V. glauerti | Mertens, 1957 | Glauert's monitor, Kakadu sand goanna, Kimberley rock monitor | ![]() |
V. hamersleyensis | Maryan, Oliver, Fitch & O'Connell, 2014 | Hamersley Range rock monitor, Southern Pilbara rock goanna | ![]() |
V. mitchelli | Mertens, 1958 | Mitchell's water monitor | ![]() |
V. pilbarensis | Storr, 1980 | Pilbara rock monitor | |
V. scalaris | Mertens, 1941 | banded tree monitor, spotted tree monitor | |
V. semiremex | W. Peters, 1869 | rusty monitor | |
V. similis | Mertens, 1958 | similis monitor, spotted tree monitor | |
V. timorensis | Gray, 1831 | spotted tree monitor, Timor monitor | ![]() |
V. tristis | Schlegel, 1838 | black-headed monitor, black-tailed monitor, freckled monitor, mournful monitor, racehorse monitor | |
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.
Varanus timorensis, the Timor monitor or spotted tree monitor, is a species of small monitor lizards native to the island of Timor and some adjacent islands.
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.
The spiny-tailed monitor, also known as the Australian spiny-tailed monitor, the ridge-tailed monitor the Ackie dwarf monitor, and colloquially simply ackie monitor, is an Australian species of lizard belonging to the genus of monitor lizards (Varanus).
The peacock monitor, also known commonly as Auffenberg's monitor, is a species of small monitor lizard in the family Varanidae. The species, which belongs to the subgenus Odatria, is endemic to Rote Island, Indonesia.
The Kimberley rock monitor is a medium-sized species of monitor lizard in the family Varanidae. The species is native to Northern Australia. Also known commonly as Glauert's monitor and the Kakadu sand goanna, it belongs to the subgenus Odatria.
The black-headed monitor or black-tailed monitor is a relatively small species of monitor lizards native to Australia. It is occasionally also called the mournful monitor, freckled monitor or the racehorse monitor, a name it shares with the Gould's monitor due to their exceptional speed. It is placed in the subgenus Odatria.
The black-spotted ridge-tailed monitor, also called commonly the black-spotted spiny-tailed monitor, the lemon-throated monitor, the northern ridge-tailed monitor, Whites monitor, and the yellow-throated monitor, is a subspecies of lizard in the family Varanidae. The subspecies is native to Australia's tropical Northern Territory. It is listed as Least Concern on the IUCN Red List as it is considered common and not threatened. It was first described in 1987. It is also known as White's dwarf goanna.
The black rough-necked monitor is a species of monitor lizard found in Southeast Asian countries of Thailand, Burma, and Malaysia. It is also found in Indonesia on Sumatra and islands of the Riau Archipelago It is sometimes known simply as the roughneck monitor. In Thailand is called h̄èā cĥāng.
The blue-tailed monitor, blue-tailed tree monitor or Kalabeck's monitor, is a monitor lizard of the Varanidae family. It belongs to the V. doreanus group of the subgenus Euprepiosaurus.
The black-palmed rock monitor is a member of the Varanidae family found in Australia. Also known as the twilight monitor or the long-tailed rock monitor, it is a member of the subgenus Odatria, and is found in the northern part of Australia in the Northern Territory and Western Australia, as well as Queensland. Specifically, its distribution extends from Mount Isa in the east to the Kimberleys in the west. Its habitat is areas of rock escarpment, and large populations may be found in small areas.
The rusty desert monitor is a species of small monitor lizards native to Australia. It is also known as the pygmy desert monitor. The monitor lizard belongs to the subgenus Odatria along with the pygmy mulga monitor. This monitor lizard is oviparous as with other monitor lizards.
Varanus spinulosus, the Solomon Island spiny monitor, Isabel monitor, or spiny-neck monitor, is a species of monitor lizard. It is endemic to the Solomon Islands archipelago and is also known from Santa Isabel Island, San Jorge Island and Bourgainville Island.
Storr's monitor is a species of monitor lizard in the family Varanidae. The species is endemic to Australia.
Plasmodium auffenbergi is a parasite of the genus Plasmodium subgenus Carinamoeba.
The Yuwono monitor or tricolor monitor, also commonly known as the black-backed mangrove monitor or the black-backed monitor, is a species of monitor lizard in the blue-tailed monitor species complex. The tricolor monitor is endemic to the island of Halmahera, in the Maluku Islands, Indonesia.
Varanus, commonly known as true monitors, is one of the 11 subgenera of the genus Varanus. All of its species are found in the Australasian realm, among which are the world's largest lizards.
Empagusia is a subgenus of monitor lizards in South to Southeast Asia, which includes medium to large species.
Soterosaurus is a subgenus of monitor lizards commonly known as Southeast Asian water monitors. Most species are endemic to the Philippines, but black rough-necked monitors, Asian water monitors, and Togian water monitors can be found elsewhere in Southeast Asia.