Lacertilia

Lacertilia is the traditional name given to the lizards, a suborder of reptiles within the order Squamata. In older or non-phylogenetic classifications, Lacertilia served as a formal grouping that encompassed most lizard lineages, distinct from snakes (Serpentes). Modern phylogenetic studies have shown that Lacertilia is not a monophyletic group because snakes share a common ancestry with lizard lineages, and some schemes place related worm lizards (amphisbaenians) in nearby branches. As a result, many contemporary treatments avoid using Lacertilia as a formal clade, preferring terminology that reflects the broader Squamata or Lepidosauria framework.

The diversity of lizards is vast, with more than 6,000 described species. They occupy a wide range of ecosystems across all continents and many islands, from deserts and grasslands to tropical forests and arid scrublands. Many lizards are arboreal, some are highly specialized ambush or active predators, and a few have aquatic or semi-aquatic habits. Diets range from insectivory and omnivory to herbivory in certain groups; some larger species are opportunistic carnivores.

Anatomically, lizards typically possess a scaly skin, movable eyelids, and well-developed limbs in many species, though limb reduction or loss has occurred in several lineages. Reproduction is highly variable: most species lay eggs (oviparous), but a considerable number of lineages give birth to live young (viviparous). Growth and development show marked variation across families and habitats.

Taxonomically, Lacertilia remains a historical reference rather than a universally accepted clade in modern systematics. Current classifications usually place lizards within Squamata, subdivided into major groups such as Iguania and Scleroglossa, with snakes and amphisbaenians included elsewhere within Squamata.