Scleroglossa is a group of

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

s that includes

gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates. They range from . Geckos are unique among lizards ...

s, autarchoglossans ( scincomorphs, anguimorphs,

snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...

s and varanoids), and

amphisbaenian Amphisbaenia (called amphisbaenians or worm lizards) is a group of typically legless lizards, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. As ...

s. Scleroglossa is supported by

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses that use morphological features (visible anatomical features). According to most morphological analyses, Scleroglossa is the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of the clade

Iguania Iguania is an infraorder of squamate reptiles that includes iguanas, chameleons, agamids, and New World lizards like anoles and phrynosomatids. Using morphological features as a guide to evolutionary relationships, the Iguania are believed ...

, which includes

iguana ''Iguana'' (, ) is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described by Austrian naturalist Josephus Nicolaus Laurenti, J.N. Laurenti in ...

chameleon Chameleons or chamaeleons (Family (biology), family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 200 species described as of June 2015. The members of this Family (biology), family are best known for ...

s, agamids, and New World lizards. Together, Scleroglossa and Iguania make up the

crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor ...

Squamata, the smallest evolutionary grouping to include all living lizards and snakes. The name Scleroglossa is derived from the Greek, ''skleros'', meaning "hard" and ''glossa'', meaning "tongue". The split between Scleroglossa and Iguania can be based on features of the tongue; iguanians have a muscular tongue and use lingual prehension to capture food, whereas scleroglossans have hard tongues and use teeth-and-jaw prehension to capture food, freeing the tongue for chemosensory activity. Recent phylogenetic analyses based on molecular data (such as DNA sequences) nest iguanians deeper within Squamata along with

snakes Snakes are elongated Limbless vertebrate, limbless reptiles of the suborder Serpentes (). Cladistically Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales much like other members of ...

and anguimorphs. Under this phylogeny, Scleroglossa is not a valid grouping. A new clade Bifurcata (bifurcated tongue) has been proposed to include Iguania as a sister taxon to Anguimorpha.Vidal, N. and Hedges, S.B. 2005
The phylogeny of squamate reptiles (lizards, snakes, and amphisbaenians) inferred from nine nuclear protein-coding genes
C.R. Biologies 328: 1000-1008.

Notes

Many studies also recognize a clade called Scincogekkonomorpha, which is a
stem-based taxon Phylogenetic nomenclature is a method of nomenclature for taxon, taxa in biology that uses phylogenetics, phylogenetic definitions for taxon names as explained below. This contrasts with Biological classification, the traditional method, by which ...
defined to include all lizards more closely related to geckos and skinks than to iguanas. Scleroglossa was first established as a
node-based taxon Phylogenetic nomenclature is a method of nomenclature for taxon, taxa in biology that uses phylogenetics, phylogenetic definitions for taxon names as explained below. This contrasts with Biological classification, the traditional method, by which ...
, defined to include Gekkota and Autarchoglossa. Therefore, Scincogekkonomorpha rather than Scleroglossa is the proper sister taxon of Iguania.

References

Tetrapod unranked clades Scincogekkonomorpha {{lizard-stub