Approximately 100 species and 12-15 genera in three extant subfamilies (Anguinae, Diploglossinae, and Gerrhonotinae) comprise Anguidae. Anniellidae is considered by many herpetologists to be a subfamily (Anniellinae) of Anguidae rather than a separate family. Anguines are found in Europe, Asia, eastern North America, and northern Africa; diploglossines in Mexico, South America, and Caribbean islands; gerrhonotines in North and Central America. Anguids occupy habitats from xeric to tropical.
Characters uniting Anguidae include a reduced supratemporal arch, a lateral fold in the skin (in most taxa), striations on the medial faces of the tooth crowns, and body osteoderms on the ventral skin. Rectangular scales make the skin appear armored. Anguidae encompasses a large diversity of body types; several species of Anguidae are quite small and limbless, others are limbless but rather long, while still others (mostly gerrhonotines) have strong but short limbs and relatively large triangular heads with powerful jaws. Anguids range in size from less than 10 cm up to about 1-1.5 m.
Anguids are carnivorous foragers, eating primarily insects, although larger species have also been known to eat small lizards, amphibians, and juvenile birds.
Anguidae includes both oviparous and ovoviviparous species, and both types of reproduction may occur in a single genus. Anguids are primarily terrestrial or semi-fossorial. One genus, Abronia, is arboreal.
Anguids have no economic value to humans. Some species are popular in the pet trade. Anguis fragilis in Britain faces severe habitat loss, and is legally protected there. Various anguid species are listed as "Endangered, vulnerable or rare" in IUCN's Redlist.
Anguidae belongs to the larger group Diploglossa (=Anguioidea), which also includes Xenosauridae (knob-scaled lizards) and Anniellidae, although Diploglossa is probably not a natural group. Diploglossa belongs to Anguimorpha, a large group that includes the varanoids Helodermatidae (Gila monsters), Lanthanotidae (earless monitor), and Varanidae (monitor lizards).
Glyptosaurinae, a subfamily of Anguidae composed entirely of extinct forms, has the most complete fossil record of any known lizards. The oldest fossils are from North America, and include Odaxosaurus (late Cretaceous), and Proxestops (Paleocene); these fossils are numerous in the Paleocene. Larger forms replace these fossils as the Tertiary progressed, and include Helodermoides (Eocene). Non-glyptosaurine anguid fossils include the annielline Apodosauriscus and the diploglossine Eodiploglossus. Several Oligocene and later fossils can be referred to modern genera.
The name "glass lizards" derives from tail autotomy of some species (i.e., some species can shatter their tails like glass to escape predation). "Alligator lizards" refers to the thick osteodermal skin and rectangular scales of some species. The limbless Anguis fragilis from England is colloquially known as the slow worm.
Gauthier, J. A. 1982. Fossil xenosaurid and anguid lizards from the early Eocene Wasatch Formation, southeast Wyoming, and a revision of the Anguioidea. Contributions to Geology, University of Wyoming, 21(1): 7-54.
Macey, J. R., J. A. Schulte II, A. Larson, B. S. Tuniyev, N. Orlov, and T. J. Papaenfuss. 1999. Molecular phylogenetics, tRNA evolution, ands historical biogeography in anguid lizards and related taxonomic families. Mol. Phylo. Evol. 12: 250-272.
Meszoely, C. A. M. 1970. North American fossil anguid lizards. Mus. Comp. Zool. Bull. 139: 87-149.
Rieppel, O. 1980. The phylogeny of anguinomorph lizards. Birkhäuser Verlag, Basel.
Jennifer C. Ast (author).