Two species in one genus, Anniella, comprise Anniellidae. Anniellidae is considered by many herpetologists to be a subfamily (Anniellinae) of Anguidae rather then a separate family. Anniellids are found in semi-arid regions in southern coastal California and Baja, Mexico. Anniellids burrow through loose, well-drained soil and leaf litter.
Characters that distinguish anniellids from other Anguimorphs include extensive parietal downgrowths, reduction in the tympanic crest of the quadrate, loss of the interclavicle, and reduction of the jugal. Anniellids have smooth scales and are cryptically colored, ranging from silvery to a darker beige. Anniellids are roughly pencil sized, about 20cm or less, and thin of body. They can autotomize their tails to avoid predation.
Anniellids burrow during day and may surface forage at night, although anniellids are rarely found on the surface. Anniellids eat insects and larvae. Domestic cats have been observed digging for these lizards; other predators include other omnivorous and carnivorous mammals, and raptors. The burrows that anniellids make may aid in soil aeration.
Anniellids are live-bearing, producing from 1-4 young in captivity. There is some evidence that they tend to avoid each other in captive and natural settings.
Anniellids have no economic importance to humans. Anniella is listed as "Endangered, vulnerable or rare" in IUCN's Redlist, and as a "Species of special concern" in California.
Anniellidae belongs to the larger group Diploglossa (Anguioidea), which also includes Anguidae (alligator lizards) and Xenosauridae (knob-scaled liazards), 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).
Fossil anniellids include Apodosauriscus from the early Eocene of Wyoming, and Pleistocene remains from California.
Gauthier, J. A. 1982. Fossil xenosaurid and anguid lizards from the early Eocen Wasatch Formation, southeast Wyoming, and a revision of the Anguioidea. Contributions to Geology, University of Wyoming, 21(1): 7-54.
Moss Landing Marine Labs, California State University consortium. 2001. http://www.anniella.org/index.html.
Rieppel, O. 1980. The phylogeny of anguinomorph lizards. Birkhäuser Verlag, Basel.
Jennifer C. Ast (author).