Scleroglossa

Scleroglossa is a clade within Squamata, one of the two principal evolutionary lineages of lizard and snake diversity, the other being Iguania. The group is defined by its shared evolutionary history and, in many classifications, by morphological and developmental traits that distinguish it from iguanian lizards.

Scleroglossa includes geckos, skinks, monitor lizards and their relatives, amphisbaenians, snakes, and several extinct lineages. In current classifications, it comprises most squamates outside Iguania. The group is cosmopolitan, with species occupying a wide range of habitats from deserts and forests to underground environments.

The clade is highly diverse in ecology and life history. Many scleroglossans exhibit cranial kinesis, allowing flexible feeding mechanics, and there is substantial variation in limb presence and reduction, with snakes and some lizard lineages showing complete or near-complete limb loss. Reproductive modes also vary, including oviparity and viviparity across different taxa.

Taxonomically, Scleroglossa is a major lineage in modern phylogenies based on molecular and morphological data. Some historical classifications used broader or different groupings, but contemporary studies consistently recognize Scleroglossa as a primary squamate clade distinct from Iguania. Ongoing research continues to refine the internal relationships among its diverse subgroups and lineages.