Iguanidae

(vertebrate zoology) A family of reptiles in the order Squamata having teeth fixed to the inner edge of the jaws, a nonretractile tongue, a compressed body, five clawed toes, and a long but rarely prehensile tail.

(Iguanidae)

Class: Reptilia

Order: Squamata

Suborder: Sauria

Family: Iguanidae

Thumbnail description
Small to large lizards, the majority of which are terrestrial and oviparous, that are marked by pleurodont teeth, which lie in inner-jaw grooves rather than in sockets

Size
1.6–30 in (30–750 cm) in snout-vent length (svl), and some have tails reaching twice the svl

Number of genera, species
69 genera; approximately 900 species

Habitat
Diverse, with most species occurring either in arid locales or wooded habitats

Conservation status
Extinct: 2 species; Critically Endangered: 6 species; Endangered: 4 species; Vulnerable: 12 species; Lower Risk/Near Threatened: 1 species; Data Deficient: 17 species

Distribution
Mainly a New World family, extending into much of North America, throughout Central America, and into South America; some species exist in other areas, including Madagascar and the islands of Polynesia

Evolution and systematics

The Iguanidae is a large family of some 860–900 species and nearly 70 genera. The iguanids comprise eight subfamilies:

• Corytophaninae, the casquehead lizards of Central America
• Crotaphytinae, the leopard and collared lizards
• Hoplocercinae, a small assemblage of South American tropical lizards
• Iguaninae, the true iguanas and spinytails
• Oplurinae, the Madagascar iguanas
• Phrynosomatinae, the tree, side-blotched, sand, spiny, and horned lizards
• Polychrotinae, the anoles
• Tropidurinae, the ground lizards of Neotropical South America and the Antilles Islands of the West Indies

The Iguanidae family is most closely related to the families Agamidae of Africa, Asia, and Australia, and the family Chamaeleonidae, mainly of Africa and Madagascar. These three families, collectively grouped as Iguania, diverged within the snake and lizard lineage very early in their evolution. Some taxonomists now classify each Iguanidae subfamily as a separate family, in which case the endings of the sub-family names listed above end in "-idae" rather than "-inae."

Physical characteristics

This large family contains species with varied appearances. Members of the Iguanidae family range from squat, toadlike horned lizards (Phrynosoma spp.) that fit in the palm of a hand, to iguanas (Iguana spp.) that are as long as a man is tall, and long-tailed and sleek anoles often seen climbing on a window screen. However, the family does have one characteristic that sets it apart from the other Iguania families. That trait is pleurodont teeth, which lie in inner-jaw grooves rather than in sockets.

The subfamilies within Iguanidae can be described in more detail. Members of the Iguaninae include the green iguana (Iguana iguana) and marine iguana (Amblyrhynchus cristatus). The typical iguanine is an imposing beast with a strong, muscular tail and (in males) a row of noticeable spines down the center of the back.

The corytophanines and polychrotines are slender-bodied lizards with long tails and long limbs. Corytophanines are generally the larger of the two, ranging in size from about 12 to 25.5 in (30.5 to 64.8 cm), compared to the 3–16 in (7.6–40.6 cm) range in the anole subfamily. The most obvious difference is the casque, or helmet, seen in the Corytophaninae subfamily. The casque is actually a tall fin on the top of the head. Corytophanines also generally have exaggerated dorsal and tail fins.

The crotaphytines and phrynosomatines are the typical lizards associated with southwestern United States. The former, which include the collared and leopard lizards, are quick, long tailed, and fairly large headed. The leopards are noted, and named, for their abundant dorsal spots, and the collared lizards usually display incomplete neck bands. The phrynosomatines are more diverse, and include more hefty-bodied species. Perhaps the most well-known phrynosomatines are the horned lizards (Phrynosoma sp.), which are often mistaken for toads because of their wide bodies and very short limbs.

The final three groups of Iguanidae are the hoplocercines, oplurines, and tropidurines. They are all small to moderately sized lizards. The first group has spiny scales; the second and third groups are distinguished more by geographic distribution (Madagascar for the second, and extreme South American areas for the third) than their appearance.

Distribution

Iguanids are largely lizards of the Western Hemisphere. They range from far southwestern Canada, into much of the United States, throughout Central America and the West Indies, and in almost all of South America except the southwestern edge. Some, like the iguanines, have wide ranges, with representatives from the southwestern United States, Central America, the northern half of South America, and the Galápagos Islands. Others, like the hoplocercines, are more restricted, with species occurring only in tropical South America.

The exceptions to the Western Hemisphere rule are the oplurines, which occur in Madagascar off the southeastern coast of Africa, and a few other species, such as Brachylophus species, that live on the Fiji Islands.

Habitat

Iguanids are almost all land-dwelling lizards. Many species, including most of the iguanines, crotaphytines, and phrynosomatines, prefer arid areas. These desert dwellers often seek sites with at least some vegetation, rocks, or other cover to provide escape routes from predators. Other iguanids seek a wooded habitat, with some, like many corytophanines, living in rain-forests. Within these varied habitats, iguanids may be either terrestrial or arboreal, with some switching between the two depending on time of day and outdoor temperature. The most unusual habitat among the iguanids is that of the well-known marine iguana of the Galápagos Islands. This lizard actually frequents salt water, where it forages marine algae to fill its diet.

Behavior

Iguanids are frequently seen stretched out on a rock or otherwise basking in the morning sun. This behavior falls under the heading of thermoregulation. Because lizards are poikilothermic, or "cold blooded," they engage in basking to raise their body temperature to prepare for the day's activities of feeding, perhaps breeding, and evading ever-present predators. Many iguanids spend the night in burrows and emerge each morning to find a sunny spot and raise their internal temperature. As the day gets hotter, ground-dwellers will move into shadier spots so they do not overheat. The more arboreal species may move from a basking spot on an outer tree limb or the sunward wall of a house to the inner branches of a tree or shrub, or closer to the ground where the temperature is lower.

The typical iguanid spends the day in a high state of alert, as predators abound, particularly for the small- and medium-sized species. Many iguanids are cryptically colored and patterned, and are best served by remaining still when a predator passes. Others are quick runners and dash off almost immediately after they spot an animal that is even remotely threatening. Favorite hiding places for these runners are crevices between or under rocks, tangles of vegetation, or anything else that provides adequate cover. Some, like the zebratailed lizard (Callisaurus draconoides), start and stop while running or abruptly change direction when momentarily out of view to confound their pursuer. Various lizards, including Uma species, conceal themselves by squirming under the sand. A few inflate their bodies to avert capture. Common chuckwallas (Sauromalus obesus) are well known for this practice, and inflate their bodies when hiding in a narrow crevice. The enlarged size makes them nearly impossible to extract. The horned lizards also puff up their bodies, but the result is an erection of their numerous spines, an excellent deterrent against biting predators. Several species of these small lizards will go a step further if the attacker is persistent, and squirt up to one-third of their blood supply out of their eye pores. Foxes and coyotes, who are the most common recipients of this behavior, seem to find the blood distasteful and release the lizards.

Another unusual predator-avoidance strategy is employed by the so-called Jesus Christ lizards (Basiliscus sp.) that appear to "walk on water" while making their escape. Normally terrestrial, the basilisks drop into the water when threatened and race on their hind legs across the water surface. Studies have shown that fringes on the hind toes trap a bubble of air beneath their feet and keep them from sinking if they are running quickly enough. Basilisks have been known to race across water as far as 100 ft (30.5 m). Numerous other iguanids engage in bipedal running, and some are very quick sprinters, but none run across the water like the basilisks.

Behaviors between members of the same species also vary among the iguanids. Territoriality is prevalent, and many species exhibit stereotyped behaviors, such as doing repeated "push-ups" or marking their turf with secretions from femoral pores, to defend specific areas for feeding or breeding. In many species, territoriality becomes more pronounced when food resources are low. In some cases, dominance hierarchies may develop. Research on green iguanas (Iguana iguana) has shown that dominant males typically have higher levels of testosterone, as well as particularly strong jaws and enlarged femoral pores. These males were able to attain and defend prime territories against other males, and also to attract more females.

Among many species, including Cyclura carinata and Sauromalus obesus, territoriality becomes more pronounced during the breeding season. The males of some species captivate potential mates by certain actions. One of the most noticeable mating displays is the flaring of the throat fan, or dewlap, which is often seen in anoles (Anolis sp.). Anoles also flare the dewlap during territorial displays, which may include head bobbing and posturing.

Feeding ecology and diet

Most iguanids are either insectivorous or herbivorous, with the larger lizards tending toward a completely vegetarian diet. The iguanines, for instance, are primarily herbivorous as adults, but the young also eat arthropods. Some members of this family, such as Gambelia species, will eat other lizards, and a few species are cannibalistic.

The insectivorous iguanids typically either stalk their prey or wait in ambush, particularly if the lizard is cryptically colored. After striking out at an insect or other arthropod, most lizards swallow the prey quickly. The common side-blotched lizard (Uta stansburiana) engages in the unusual practice of banging the prey on the ground several times before consuming it. Horned lizards are distinguished by their diet, which consists almost wholly of ants. These small lizards must eat considerable numbers of ants to gain adequate nutrition. Since ants produce formic acid to deter predators, the lizards may smell of formic acid as a result.

Reproductive biology

Most iguanids lay eggs, but a few give birth to live young. These include some Phrynosoma, Sceloporus, and Leiolamus species, as well as Corytophanes percarinatus. The number of eggs ranges widely. Many iguanids, such as the green anole (A. carolinensis), lay only one or two eggs at a time, but others lay dozens. The horned lizard (P. cornutum) commonly lays 24 eggs, but the number sometimes reaches more than 36 per clutch. A green iguana female may lay more than 60 eggs at a time.

In many species, optimal environmental conditions can spawn additional clutches. For example, some Dipsosaurus, Crotaphytus, and Gambelia species that live in cooler climates have only one clutch each year, while warmer-climate populations may have two, three, four, or more clutches.

Parental care among most iguanids is either nonexistent, or is restricted to simply burying the eggs or engaging in short-term nest guarding. The iguanines are most known for nest guarding. The rhinoceros iguana (Cyclura cornuta cornuta), for example, lays from two to nearly three dozen eggs, then tenaciously guards her nest for several days. The Jamaican iguana (Cyclura collei) guards her nest for up to two weeks. Among the iguanines, nest-guarding behaviors may range from displays to physical attacks.

Conservation status

The 2002 IUCN Red List includes 2 iguanids as Extinct, 6 as Critically Endangered, 4 as Endangered, 12 as Vulnerable, 1 as Lower Risk/Near Threatened, and 17 as Data Deficient. The extinct species are both tropidurines: Leiocephaluseremitus and L. herminieri. In addition, other iguanid species that are not listed by the IUCN are declining in either number or range due to overcollecting or habitat disruption and destruction. Introduced species also may play a role in these declines. For example, numbers of horned lizards in southern California have dropped in association with the proliferation of Argentine ants, which are replacing the native ants that make up the bulk of the lizards' diet.

A number of conservation activities are under way to protect threatened iguanids. For example, the Jamaican iguana (Cyclura collei), was believed extinct until a dead lizard was found in 1970 and a second individual, this time a living male, was discovered 20 years later. Since that time, the Jamaican Iguana Research and Conservation Group formed to survey the lizard's present habitat, which is now limited to a small peninsula west of Kingston. The population, estimated at about 100 individuals, is faced with several threats in the wild, including predation of the eggs (and likely the young) by the Indian mongoose (Herpestes javanicus [=auropunctatus]). Researchers now hope to boost the population by gathering eggs from the wild and rearing the hatchlings at the Hope Zoo in Jamaica until the lizards are large enough to avoid predation. The Natural Resources Conservation Authority is also taking measures, including promoting the designation of the area as a national park, to protect the lizard's current habitat from deforestation and development. Other proposals include introducing the lizards to areas such as Great Goat Island, which supported a population of Jamaican iguanas through the middle of the twentieth century.

Another at-risk iguanid is the Turks and Caicos iguana (Cyclura carinata carinata), which is native to these islands north of Haiti and the Dominican Republic. The lizards were once widespread, but the population is now estimated to number about 30,000 adults, and these are restricted to the smaller islands. Introduced mammals are the largest threat. Cats and dogs prey on the lizards, and now-wild livestock competes with the mainly herbivorous lizards for vegetation. Habitat destruction is also taking a toll. In an attempt to prevent the continued decline of the lizard population, the National Trust for the Turks and Caicos Islands worked with the government to draft legislation protecting the lizards from additional introduced mammals. The trust has also trapped cats in vulnerable areas. Other efforts include recently installed viewing platforms to keep tourists away from the lizards, the introduction of tourist fees to support further conservation efforts, and new educational programs to spread the word about the lizards and their plight.

Significance to humans

Many iguanid lizards are prized as sources of food meat, particularly in the southwestern United States and Mexico. They are also a mainstay in the pet lizard trade. Perhaps most importantly, they are valued by nature lovers, who can spend hours watching the antics of the lizards.

Species accounts

Resources

Burghardt, G., and A. Rand, eds. Iguanas of the World: Their Behavior, Ecology, and Conservation. Park Ridge, NJ: Noyes Publications, 1982.

Campbell, J. A. Amphibians and Reptiles of Northern Guatemala, the Yucatan and Belize. Animal Natural History Series, Vol. 4. Norman: University of Oklahoma Press, 1998.

Cei, J. M. New Species of Tropidurus (Sauria, Iguanidae) from the Arid Chacoan and Western Regions of Argentina. Lawrence: University of Kansas, Museum of Natural History, 1982.

Cogger, H., and R. Zweifel, eds. Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press, 1998.

Conant, R., J. T. Collins, I. H. Conant, T. R. Johnson, and S. L. Collins. A Field Guide to Reptiles & Amphibians of Eastern & Central North America. Peterson Field Guide Series. Boston: Houghton Mifflin Co., 1998.

Crother, B. I., ed. Caribbean Amphibians and Reptiles. San Diego: Academic Press, 1999.

Frank, N., and E. Ramus. A Complete Guide to Scientific and Common Names of Reptiles and Amphibians of the World. Pottsville, PA: NG Publishing Inc., 1996.

Grismer, L. L., and H. W. Greene. Amphibians and Reptiles of Baja California, Including Its Pacific Islands and the Islands in the Sea of Cortês (Organisms and Environments). Berkeley: University of California Press, 2002.

Lee, J. C. A Field Guide to the Amphibians and Reptiles of the Maya World: The Lowlands of Mexico, Northern Guatemala, and Belize. Ithaca, NY: Cornell University Press, 2000.

Milstead, W., ed. Lizard Ecology: A Symposium. Columbia: University of Missouri Press, 1967.

Pianka, E. Ecology and Natural History of Desert Lizards: Analyses of the Ecological Niche and Community Structure. Princeton, NJ: Princeton University Press, 1986.

Pianka, E. R., and L. J. Vitt, eds. Lizard Ecology. Berkeley: University of California Press, 1994. ——. Lizards: Windows to the Evolution of Diversity. Berkeley: University of California Press, 2003.

Savage, J. M., M. Fogden, and P. Fogden. The Amphibians and Reptiles of Costa Rica: A Herpetofauna Between Two Continents, Between Two Seas. Chicago: University of Chicago Press, 2002.

Smith, H. M. Handbook of Lizards: Lizards of the United States and Canada. Ithaca, NY: Comstock Publishing Co., 1946.

Stebbins, R. A Field Guide to Western Reptiles and Amphibians. Boston: Houghton Mifflin Co., 1985.

Bealor, M. T., and C. Krekorian. "Chemosensory Identification of Lizard-Eating Snakes in the Desert Iguana, Dipsosaurus dorsalis (Squamata: Iguanidae)." Journal of Herpetology 36, no.1 (2002): 9–15.

Carothers, J. H. "Dominance and Competition in an Herbivorous Lizard." Behavioral Ecology and Sociobiology 8 (1981): 261–266.

Frost, D. R., and R. Etheridge. "A Phylogenetic Analysis and Taxonomy of Iguanian Lizards (Reptilia: Squamata)." University of Kansas, Museum of Natural History Miscellaneous Publications 81 (1989): 1–65.

Hager, S. B. "The Role of Nuptial Coloration in Female Holbrookia maculata: Evidence for a Dual Signaling System." Journal of Herpetology 35, no. 4 (2001): 624–632.

Hazen-Hammond, S. " 'Horny Toads' Enjoy a Special Place in Western Hearts." Smithsonian 25 (1994): 82–86.

Ramírez-Bautista, A.; O. Ramos Flores, J. W. Sites, Jr. "Reproductive Cycle of the Spiny Lizard Sceloporus jarrovii (Sauria: Phrynosomatidae) from North-Central Mexico." Journal of Herpetology 36, no. 2 (June 2002): 225–233.

Iguana Specialist Group of the World Conservation Union (IUCN). Web site:

The International Iguana Society. 133 Steele Rd., West Hartford, CT 06119 USA. Web site:

Pianka, E. R., and W. L. Hodges. Horned Lizards. (cited November 4, 2002).

Proliferation of Argentine Ants in California Linked to Decline in Coastal Horned Lizards. February 26, 2002 (cited November 4, 2002).

[Article by: Leslie Ann Mertz, PhD]

The noun has one meaning:

Meaning #1: New World lizards
  Synonyms: family Iguanidae, Iguania, family Iguania

Iguanas
Green iguana (Iguana iguana)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Order:	Squamata
Suborder:	Iguania
Family:	Iguanidae
Genera
Amblyrhynchus Brachylophus Conolophus Ctenosaura Cyclura Dipsosaurus Iguana Sauromalus

Iguanidae is a family of lizards, composed of iguanas and related species.^[1]

Contents 1 Classification of Iguanidae 1.1 Traditional classification 1.2 Frost et al. classification of iguanas 2 External links 3 References

Classification of Iguanidae

Two different classification schemes have been used to define the structure of this family. These are the "traditional" classification and the classification presented by Frost et al. (1989)^{[citation needed]}.

Frost et al. redefined this family. The genera belonging to the different subfamilies were assigned to separate families. This view is not generally accepted and the 'traditional' classification is still widely used.

Traditional classification

Family Iguanidae

• Subfamily Corytophaninae: casquehead lizards
• Subfamily Crotaphytinae: collared and leopard lizards
• Subfamily Hoplocercinae: wood lizards, clubtails
• Subfamily Iguaninae: green iguanas and spinytail iguanas
• Subfamily Leiocephalinae
• Subfamily Leiosaurinae
• Subfamily Liolaeminae
• Subfamily Oplurinae: Madagascar iguanids
• Subfamily Phrynosomatinae: earless, spiny, tree, side-blotched and horned lizards
• Subfamily Polychrotinae: anoles
• Subfamily Tropidurinae: neotropical ground lizards

Frost et al. classification of iguanas

Family Iguanidae

• Genus Amblyrhynchus
• Genus Anolis
• Genus Brachylophus
• Genus Conolophus
• Genus Ctenosaura
• Genus Cyclura
• Genus Dipsosaurus
• Genus Iguana
• Genus Sauromalus
• Genus Armandisaurus (extinct)
• Genus Gangiguana (extinct)
• Genus Lapitiguana (extinct)
• Genus Pumila (extinct)

Green Iguana sp.	Lesser Antillean Iguana, Dominica, W.I..	Marine Iguanas, Galapagos Islands.	Galapagos Land Iguana, Galapagos Islands.
Iguana found in the Florida Keys, diving into the sea.	A green iguana.	Ctenosaura similis, Tulum, Mexico

External links

• Family iguanidae

References

1. ^ Bauer, Aaron M. (1998). Cogger, H.G. & Zweifel, R.G.. ed. Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press. pp. 140–142. ISBN 0-12-178560-2. 

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