The Iguanidae are a family of lizards composed of iguanas and related species. This family consists of species such as the Green Iguana (Iguana iguana), the Lesser Antillean Iguana (Iguana delicatissima), and marine iguana (Amblyrhynchus cristatus), just to name a few.
Iguanidae is thought to be the sister group to the collared lizards (family Crotaphytidae); the two groups likely diverged during the Late Cretaceous, as that is when Pristiguana and Pariguana, the two earliest fossil genera, are known from. The subfamily Iguaninae, which contains all modern genera, likely originated in the earliest Paleocene, at about 62 million years ago. The most basal extant genus, Dipsosaurus, diverged from the rest of Iguaninae during the late Eocene, about 38 million years ago, with Brachylophus following a few million years later at about 35 million years ago, presumably after its dispersal event to the Pacific. All other modern iguana genera formed in the Neogene period.
A phylogenetic tree of Iguaninae is shown here:
Iguanas and iguana-type species are diverse in terms of size, appearance, and habitat. They typically flourish in tropical, warm climates, such as regions of South America and islands in the Caribbean and in the Pacific. Iguanas typically possess dorsal spines across their back, a dewlap on the neck, sharp claws, a long whip-like tail, and a stocky, squat build. Most iguanas are arboreal, living in trees, but some species tend to be more terrestrial, which means they prefer the ground. Iguanas are typically herbivores and their diets vary based on what plant life is available within their habitat. Iguanas across many species remain oviparious, and exhibit little to no parental care when their eggs hatch. They do, however, display nest-guarding behavior. Like all reptiles, they are poikilothermic, and also rely on regular periods of basking under the sun to thermoregulate.
All but one of modern iguana genera are native to the Americas, ranging from the deserts of the Southwestern United States through Mexico, Central America, and the Caribbean, to throughout South America down to northernmost Argentina. Some iguanas like I. iguana have spread from their native regions of Central and South America into many Pacific Islands, and even to Fiji, Japan, and Hawai'i, due to the exotic pet trade and illegal introductions into the ecosystems. Other iguanas, like the Galapagos pink iguana (C. marthae) are endemic only to specific regions on the Galapagos islands. The Grand Cayman blue iguana, C. lewisi, is endemic only to the Grand Cayman island, limited to a small wildlife reserve. The only non-American iguana species are the members of the genus Brachylophus and the extinct Lapitiguana, which are found on Fiji and formerly Tonga; their distribution is thought to be the result of the longest overwater dispersal event ever recorded for a vertebrate species, with them rafting over 8000 km across the Pacific from the Americas to the Fiji and Tonga.
Several classification schemes have been used to define the structure of this family. The "historical" classification recognized all New World iguanians, plus Brachylophus and the Madagascar oplurines, as informal groups and not as formal subfamilies.
Frost and Etheridge (1989) formally recognized these informal groupings as families.
Macey et al. (1997), in their analysis of molecular data for iguanian lizards recovered a monophyletic Iguanidae and formally recognized the eight families proposed by Frost and Etheridge (1989) as subfamilies of Iguanidae.
Schulte et al. (2003) reanalyzed the morphological data of Frost and Etheridge in combination with molecular data for all major groups of Iguanidae and recovered a monophyletic Iguanidae, but the subfamilies Polychrotinae and Tropidurinae were not monophyletic.
Townsend et al. (2011), Wiens et al. (2012) and Pyron et al. (2013), in the most comprehensive phylogenies published to date, recognized most groups at family level, resulting in a narrower definition of Iguanidae.
- Informal grouping anoloids: anoles, leiosaurs, Polychrus
- Informal grouping basiliscines: casquehead lizards
- Informal grouping crotaphytines: collared and leopard lizards
- Informal grouping iguanines: marine, Fijian, Galapagos land, spinytail, rock, desert, green, and chuckwalla iguanas
- Informal grouping morunasaurs: wood lizards, clubtails
- Informal grouping oplurines: Madagascan iguanids
- Informal grouping sceloporines: earless, spiny, tree, side-blotched and horned lizards
- Informal grouping tropidurines: curly-tailed lizards, South American swifts, neotropical ground lizards
Frost et al. (1989) classification of iguanas
Macey et al. (1997) classification of Iguanidae
- Subfamily Corytophaninae: casquehead lizards
- Subfamily Crotaphytinae: collared and leopard lizards
- Subfamily Hoplocercinae: wood lizards, clubtails
- Subfamily Iguaninae: marine, Fijian, Galapagos land, spinytail, rock, desert, green, and chuckwalla iguanas
- Subfamily Oplurinae: Madagascan iguanids
- Subfamily Phrynosomatinae: earless, spiny, tree, side-blotched and horned lizards
- Subfamily Polychrotinae: anoles, leiosaurs, Polychrus
- Subfamily Tropidurinae: curly-tailed lizards, neotropical ground lizards, South American swifts
Schulte et al. (2003) classification of Iguanidae
Here families and subfamilies are proposed as clade names, but may be recognized under the traditional Linnean nomenclature.
Corytophaninae: casquehead lizards
Crotaphytinae: collared and leopard lizards
Hoplocercinae: wood lizards, clubtails
Iguaninae: marine, Fijian, Galapagos land, spinytail, rock, desert, green, and chuckwalla iguanas
Oplurinae: Madagascan iguanids
Phrynosomatinae: earless, spiny, tree, side-blotched and horned lizards
Polychrotinae: anoles, leiosaurs, Polychrus
- subclade of Polychrotinae Anolis: anoles
- subclade of Polychrotinae Leiosaurini: leiosaurs
Tropidurinae: curly-tailed lizards, neotropical ground lizards, South American swifts
- subclade of Tropidurinae Leiocephalus: curly-tailed lizards
- subclade of Tropidurinae Liolaemini: South American swifts
- subclade of Tropidurinae Tropidurini: neotropical ground lizards
Townsend et al. (2011), Wiens et al. (2012) and Pyron et al. (2013) classification of Iguanidae
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