|Green iguana (Iguana iguana)|
Laurenti, in 1768
Iguana (//, Spanish: [iˈɣwana]) is a genus of omnivorous lizards native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena. Two species are included in the genus Iguana: the green iguana, which is widespread throughout its range and a popular pet, and the Lesser Antillean iguana, which is native to the Lesser Antilles and endangered due to habitat destruction.
In addition to the two species in the genus Iguana, several other related genera in the same family have common names of the species including the word "iguana".
Anatomy and Physiology
Iguanas can range from 1.5 to 1.8 metres (5 to 6 ft) in length, including their tail. The two species of lizard within the genus Iguana possess a dewlap, a row of spines running down their backs to their tails, and a tiny "third eye" on their heads. This light-sensing organ is known as the parietal eye, visible as a pale scale on the top of the head, and cannot make out details, just brightness. Behind their necks are small scales which resemble spokes, known as tuberculate scales. These scales may be a variety of colors and are not always visible from close distances. They have a large round scale on their cheeks known as a subtympanic shield.
Iguanas have keen vision and can see shapes, shadows, colors, and movement at long distances. Their visual acuity enables them to navigate through crowded forests and to locate food. They employ visual signals to communicate with other members of the same species.
The tympanum, the iguana's eardrum, is located above the subtympanic shield (or "earshield") behind each eye. Iguanas are often hard to spot, as they tend to blend into their surroundings and their coloration enables them to hide from larger predators.
Skull Morphology and Diet
Iguanas have developed an herbivorous lifestyle, foraging exclusively on vegetation and foliage. In order to acquire, process, and digest plant matter herbivorous lizards must have a higher bite force relative to their size (when compared to carnivorous or omnivorous reptiles). The skull of the iguana has undergone modifications resulting in a strong bite force and efficient processing of vegetation, according to one study.
In order to accomplish this biomechanically, herbivorous lizards (such as the iguana) have taller and wider skulls, shorter snouts, and larger bodies relative to carnivorous and omnivorous reptiles. Increasing the robusticity of the skull allows for increased muscle presence and increases the ability of the skull to withstand stronger forces.
Furthermore, the teeth of the iguana are acrodontal, meaning that their teeth sit on top of the surface of the jaw bone and project upwards. The teeth themselves are small and serrated - designed for grasping and shearing food.
|Wikimedia Commons has media related to Iguana.|
- Cambridge Dictionary
- Oxford Dictionaries
- Coles, William (2002), "Green Iguana" (PDF), U.S.V.I. Animal Fact Sheet #08, Department of Planning and Natural Resources US Virgin Islands Division of Fish and Wildlife
- Lazell, J.D. (1973), "The lizard genus Iguana in the Lesser Antilles", Bulletin of the Museum of Comparative Zoology, New York, 145, pp. 1–28
- Lichtenbelt, Wouter D. van Marken (1993-08-01). "Optimal foraging of a herbivorous lizard, the green iguana in a seasonal environment". Oecologia. 95 (2): 246–256. doi:10.1007/BF00323497. ISSN 0029-8549.
- Metzger, Keith A.; Herrel, Anthony (2005-12-01). "Correlations between lizard cranial shape and diet: a quantitative, phylogenetically informed analysis". Biological Journal of the Linnean Society. 86 (4): 433–466. doi:10.1111/j.1095-8312.2005.00546.x. ISSN 0024-4066.
- Herrel, Anthony (2009). "Jaw and hyolingual muscle activity patterns and bite forces in the herbivorous lizard Uromastyx acanthinurus". Archives of Oral Biology. 54: 772–782.
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- Frost, D.E. and R.E. Etheridge (1989) A Phylogenetic Analysis and Taxonomy of Iguanian Lizards (Reptilia: Squamata). Univ. Kansas Mus. Nat. Hist. Misc. Publ. 81
- Frost, D.R., R. Etheridge, D. Janies and T.A. Titus (2001) Total evidence, sequence alignment, evolution of Polychrotid lizards, and a reclassification of the Iguania (Squamata: Iguania). American Museum Novitates 3343: 38 pp.