Lizards are a group of reptiles that includes all scaly reptiles other than snakes. They usually have four legs, long bodies, tails, eyelids, and external ears. Lizards are the most diverse group of reptiles and include many well-known animals such as iguanas, geckos, and skinks.
Where are lizards found?
Lizards are found almost everywhere on Earth with the major exception being their absence from the Antarctic continent. Because lizards are cold-blooded animals (i.e. their body temperature is controlled by the ambient environment), they are more prevalent in warmer climates around the tropics and are some of the most successful vertebrate animals in desert environments. South America, in particular, the Amazon, is the diversity hotspot with more species than anywhere else in the world and many still undiscovered. The Australian continent is home to more than 620 species and there are more than 600 species in southern Africa.
The size of different lizard species can vary hugely. The smallest known species is Brookesia micro of Madagascar which was found and measured as a full grown adult at only 29 mm. The largest species on Earth is the Komodo dragon of Indonesia which can grow up to 3 m (10 ft) long and get as heavy as 70 kg (155 lbs).
What do lizards eat?
Different lizard species have a range of different diets. Many species are herbivorous, feeding only on plant material. A good example of herbivorous lizards are the iguanas which are spread around the world but are mostly vegetarians. An extreme case is the iguana species found on the Galapagos Islands, Amblyrhynchus cristatus, which feeds entirely on seaweed several meters under water.
Some species are carnivorous and eat only animals while others are omnivorous and eat both other animals and plants. The monitor lizards, a well-known genus found through many parts of the world, are mostly carnivorous while the Lilford’s wall lizard, Podarcis lilfordi, is an endangered omnivorous species. Most species live on a diet of fruit and insects but some larger species, such as the Komodo dragon and monitor lizards, will also feed on larger animals such as pigs and even buffalos.
How do lizards reproduce?
Most species reproduce by laying eggs from which hatchlings emerge. Some species give birth to live young. The reproductive cycle of a lizard is similar to many other animals and controlled by external factors such as temperature, food supply, rainfall, and day length.
Taxonomy of lizards
Lizards belong to an order of reptiles known as the Squamata, which also includes snakes. Within the lizard group, there are four infraorders:
- Iguania – separated into a number of families. Includes the iguanas and chameleons and a number of other lizards.
- Gekkota – six families including two families of geckos.
- Scinomorpha – includes skinks, wall lizards, and other species.
- Anguimorpha – six families including the Anguidae family which has many legless lizards.
- Amphisbaenia – the worm lizards. Includes five families with species that often resemble earthworms.
Diversity and evolution of lizards
Globally, the total diversity of lizards is more than 5000 species. They have the largest diversity of any of the reptilian group and make up more than half of all reptile species. The largest genus of lizards is a genus of iguana, known as Anola, which has more than 400 species.
Lizards are known to have evolved more than 200 million years ago, 100 millions years before mammals. Lizard-like fossils have been dated back to the Triassic period which spans from 252.2-201.3 million years ago.
- Lizards, along with snakes, shed their skins when they grow too large for them.
- Some species of lizards have evolved the ability to drop their tail off if they are attacked and then regrow it.
- Lizards are cold-blooded animals and their body temperatures are dependent on the ambient temperature. If it is too cold, they are unable to move quickly because their metabolism slows down too much.
Last edited: 17 December 2015