The horns on a chameleon are made up of ringlike segments of inner bone covered by a hard keratin-like skin.
The oldest known chameleon fossil is from the extinct species Chamaeleo caroliquarti. It was found in Europe and is 26 million years old.
Chameleons change color by rearranging a lattice of nanocrystals in one of their top layers of skin cells called iridophores. Chameleons can then stretch this layer, broadening the nanocrystalline lattice, thereby causing it to reflect a different wavelength of light.
The word Brookesia is named after the British naturalist Joshua Brookes.
Chameleons do not have external ears or a tympanic membrane, but they do have internal ears as well as degenerated middle ears. They do not hear well but they can detect low frequency sounds.
True chameleons include the following genera: Archaius, Bradypodion, Brookesia, Calumma, Chamaeleo, Furcifer, Kinyongia, Nadzikambia, Palleon, Rhampholeon, Rieppeleon and Trioceros.
Chameleons have laterally compressed bodies. This enables them to warm up quickly by presenting a larger surface area to the sun. It also helps some chameleon species blend in among the similarly shaped leaves in their environment.
Chamaeleo namaquensis is found in the desert of Namibia. To cool off it will sometimes bury itself in the sand.
Trioceros schubotzi can be found at elevations as high as 4500m.
Some chameleons play dead to avoid predation; this is called thanatosis.