What is a Lizard?
Lizards are a type of reptile which are part of the order squamata and the suborder lacertilia. Their closest relatives are the snakes and the legless lizards such as the sheltopusik have no legs.
This suborder is made up of 40 different families which share physical characteristics.
This group is the most successful of the reptiles. There appearance is highly variable and it difficult to define the traits which they share.
Three broad traits are used to place lizards in this group. This is that they are scaly skinned reptiles which have legs, moveable eyelids and an external ear opening. Despite this many lizards lack one of these features. The glass lizards have lost or have degenerated limbs, a number of geckoes, skinks and night lizards have lost their moveable eyelid and some lack the external ear opening.
A number of lizard species are able to break off their tail and then regrow it. This is known as autonomy. There are points in there vertebrae known as fracture plates which are weak points where the tail can break off.
They will smell by sticking out their tongue to gather scent particles which are then processed by sensory cells which are located on the roof of their mouth.
Two species of lizard are considered venomous, these are the Mexican beaded lizard and the gila monster. Recent research suggests other species such as the Komodo dragon may be venomous.
Types of Lizard
Lizards have been the subject of much debate in relation to their grouping. Currently four superfamilies have been widely accepted and details on these are below.
Iguanas and their Relatives
The superfamily iguania is made up of three families the iguanids, agamids and chameleons. The iguanaids and agamids are similar with most living on the ground and having small scales. The chameleons mostly live in trees.
Most of these lizards have the ability to change color though this is different for each species.
Geckoes and Snakes Lizards
The gekkota superfamily includes seven families. The geckoes are mostly small, nocturnal lizards. Most of the geckoes lack an eyelid though there are exceptions to this. Snake lizards lack legs instead having scaly flaps. This group also includes the blind lizards which have eyes covered with scales and can be found in underground burrows.
Skinks and their Relatives
Skinks and their relatives form the largest superfamily within the lizards. They are primarily long, slender lizards with legs though some have lost these. Some burrowing species have lost the moveable eyelids replacing it with a transparent, fused eyelid. Some of these lizards develop inside their mother attached to a placenta similar to that of mammals.
These lizards are believed to be the ancestors of the snakes with many members of this group sharing their long, forked tongue. They also have fang like teeth.
The anguimporh lizards superfamily includes 7 subfamilies and species such as the monitors and the venomous lizards, the gila monster and the Mexican beaded lizard.
It is estimated that there are more than 5,000 lizards found across the globe. The largest lizard on Earth is the Komodo dragon which can reach up to 3m (10ft) long and weigh as much as 80kg (176lbs). The smallest are two species of dwarf gecko which measure up to 1.6cm (0.6in).
Lizard Fact Files
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