Chameleon

Chameleons or chamaeleons (family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 202 species described as of June 2015. These species come in a range of colors, and many species have the ability to change colors. Chameleons are distinguished by their zygodactylous feet; their very long, highly modified, rapidly extrudable tongues; their swaying gait and crests or horns on their brow and snout. Most species, the larger ones in particular, also have a prehensile tail. Chameleons' eyes are independently mobile, but in aiming at a prey item, they focus forward in coordination, affording the animal stereoscopic vision. Chameleons are adapted for climbing and visual hunting. They live in warm habitats that range from rain forest to desert conditions, various species occurring in Africa, Madagascar, southern Europe, and across southern Asia as far as Sri Lanka. They also have been introduced to Hawaii,California, and Florida, and often are kept as household pets.

Description[edit]

Malagasy giant chameleon, Ambalavao, Madagascar

Cape dwarf chameleon in the act of defecation: the typical action by which it avoids fouling its own branch incidentally displays the difference between the arrangement of its fore and hind toes.

Nearly all species of chameleon have prehensile tails, but they most often grip with the tail when they cannot use all four feet at once, such as when passing from one twig to another.

Chameleons vary greatly in size and body structure, with maximum total lengths varying from 15 mm (0.59 in) in male Brookesia micra (one of the world's smallest reptiles) to 68.5 cm (27.0 in) in the male Furcifer oustaleti.^[27][28] Many have head or facial ornamentation, such as nasal protrusions, or horn-like projections in the case of Trioceros jacksonii, or large crests on top of their heads, like Chamaeleo calyptratus. Many species are sexually dimorphic, and males are typically much more ornamented than the female chameleons.

Typical sizes of species of chameleon commonly kept as pets are:

Scientific name	Common name	Length (male)	Length (female)	Color	Lifespan (years)
Chamaeleo calyptratus	Veiled chameleon	35–60 cm	25–33 cm	Green and light colors	about 5
Trioceros jacksonii	Jackson's chameleon	23–33 cm	25–33 cm	Green and light colors	5–10
Furcifer pardalis	Panther chameleon	38–53 cm	23–33 cm	Darker colors	about 5 (2–3 for birthing females)
Rieppeleon brevicaudatus	Bearded pygmy chameleon	5–8 cm	5–8 cm	Brown, beige, green	about 3–5
Rhampholeon spectrum	Spectral pygmy chameleon	8–10 cm	5–10 cm	Tan and gray	3–5
Rhampholeon temporalis	Usambara pitted pygmy chameleon	6–10 cm	5–9 cm	Gray and brown	5–11

The feet of chameleons are highly adapted to arboreal locomotion, and species such as Chamaeleo namaquensis that have secondarily adopted a terrestrial habit have retained the same foot morphology with little modification. On each foot, the five clearly distinguished toes are grouped into two fascicles. The toes in each fascicle are bound into a flattened group of either two or three, giving each foot a tongs-like appearance. On the front feet, the outer, lateral, group contains two toes, whereas the inner, medial, group contains three. On the rear feet, this arrangement is reversed, the medial group containing two toes, and the lateral group three. These specialized feet allow chameleons to grip tightly onto narrow or rough branches. Furthermore, each toe is equipped with a sharp claw to afford a grip on surfaces such as bark when climbing. It is common to refer to the feet of chameleons as didactyl or zygodactyl, though neither term is fully satisfactory, both being used in describing totally different feet, such as the zygodactyl feet of parrots or didactyl feet of sloths or ostriches, none of which is significantly like chameleon feet. Although "zygodactyl" is reasonably descriptive of chameleon foot anatomy, their foot structure does not resemble that of parrots, to which the term was first applied. As for didactyly, chameleons visibly have five toes on each foot, not two.

Some chameleons have a crest of small spikes extending along the spine from the proximal part of the tail to the neck; both the extent and size of the spikes varies between species and individuals. These spikes help break up the definitive outline of the chameleon, which aids it when trying to blend into a background.