(Xantusiidae)
Class: Reptilia
Order: Squamata
Suborder: Scincomorpha
Family: Xantusiidae
Thumbnail description
Small to medium-sized lizards lacking eyelids and having enlarged plates on the dorsal surface of the head and transverse rows of enlarged scales on the belly
Size
1.5–5 in (3.7–12.7 cm) snout-vent length
Number of genera, species
3 genera, 23 species
Habitat
Deserts to rainforests
Conservation status
Vulnerable: 1 species
Distribution
North America, Central America, Cuba
Evolution and systematics
Xantusiidae represents an ancient reptile lineage of uncertain relationships. The question what group of lizards constitutes the nearest relatives of Xantusiidae has long puzzled herpetologists. Night lizards resemble geckos in some features, but in other characteristics they appear more allied with teiids, lacertids, and skinks. Although the question continues to be debated by systematists, current evidence seems to indicate that xantusiids are probably most closely related to one of the latter three families, but which one remains a mystery. The fossil record extends back to the Paleocene, but it has shed little light on the origins of the family.
Also controversial is the question of relationships among the three living genera: Cricosaura (1 species), Lepidophyma (17 species), and Xantusia (5 species). Evidence from DNA sequences and from chromosomes indicates that the Cuban night lizard (Cricosaura typica) is the oldest separate lineage in the family, whereas characteristics based on internal and external morphology have been interpreted as evidence that Xantusia is the earliest branch. Subfamilies have been recognized within Xantusiidae but are not used in this account because of the small number of genera and the ambiguity of the evidence of relationships among them.
Physical characteristics
The most distinctive external feature of Xantusiidae is the lack of eyelids. The eyes are covered by a large, transparent scale ("spectacle" or brille) similar to that in snakes and many geckos. The family often is erroneously said to be characterized by having vertically elliptical pupils, but this condition is present only in Xantusia. Cricosaura and Lepidophyma have round pupils. The belly is covered by a series of transverse rows of large, rectangular scales, and there are enlarged plates on the dorsal surface of the head. Body size differs tremendously among the species, from a maximum snout-vent length of only 1.5 in (3.7 cm) for the desert night lizard (Xantusia vigilis) to 5 in (12.7 cm) for the yellow-spotted night lizard (Lepidophyma flavimaculatum).
Distribution
Xantusiidae is a strictly New World family. Members of Xantusia are found in the southwestern United States and northwestern Mexico. The Cuban night lizard occurs only in a small area on Cuba. The species of Lepidophyma are found from Nuevo Leon, Mexico, south to Panama. Xantusiids live from sea level to an elevation of more than 9,000 ft (2,700 m).
Habitat
Night lizards are habitat specialists. Many of the species are restricted to particular microhabitats. Some species are found primarily in decaying yuccas and agaves. Others live only in rock crevices, caves, or rainforest litter.
Behavior
Because of their secretive and reclusive nature, night lizards are seldom found active outside cover, and little is known about their behavior. Despite the name, night lizards are not strictly nocturnal and may be active day or night, depending on temperature and other conditions. The English name appears to be based on the presence of elliptical pupils in members of the genus Xantusia. Night lizards have a low preferred body temperature and low metabolic rate.
Feeding ecology and diet
Some species of Xantusiidae are strictly insectivorous. Others have a diet that includes plant material. Whether any are exclusively herbivorous is unclear. These lizards search for food primarily within the confines of their cover, such as decaying logs.
Reproductive biology
All species for which reproductive information is available are live-bearing, with one notable exception. Recent observations indicate that the Cuban night lizard is egg-laying.
Conservation status
Only one species, the island night lizard (Xantusia river-siana), is officially listed as Vulnerable. The listing of this species is based on its limited distribution (three California islands) and threats to the populations posed by introduced animals, particularly pigs and goats. Most of the species in the genus Lepidophyma have restricted distribution and have been severely affected by the decimation of forests in tropical America.
Significance to humans
Because of their secretive habits, night lizards are seldom seen or appreciated by humans. In some regions they are feared because of the mistaken notion that they are venomous.
Species accounts
Desert night lizardYellow-spotted night lizard
Cuban night lizard
Resources
Books:Alvarez del Toro, M. Los reptiles de Chiapas. 3rd edition. Chiapas: Instituto de Historia Natural, Tuxtla Gutierrez, 1982.
Campbell, J. A. Amphibians and Reptiles of Northern Guatemala, the Yucatan, and Belize. Norman: University of Oklahoma Press, 1998.
Estes, R. Sauria terrestria, Amphisbaenia. Vol. 10A, Handbuch der Palaeoherpetologie. Stuttgart: Gustav Fisher Verlag, 1983.
Mautz, W. J. "Ecology and Energetics of the Island Night Lizard, Xantusia riversiana, on San Clemente Island." In Third California Islands Symposium: Recent Advances in Research on the California Islands, edited by F. G. Hochberg. Santa Barbara: Santa Barbara Museum of Natural History, 1993.
Periodicals:Ansel, Fong G., M. Rolando Viña, and B. Angel Arias. "Aspectos de la Historia Natural de Cricosaura typica (Sauria: Xantusiidae) de Cuba." Caribbean Journal of Science 35 (1999): 148–150.
Bezy, R. L. "Xantusia vigilis." Catalogue of American Amphibians and Reptiles 302 (1982): 1–4. ——. "The Natural History of the Night Lizards, Family Xantusiidae." In Proceedings of the Conference on California Herpetology: Southwestern Herpetologists Society Special Publication no. 4 (1988): 1–12. ——. "Night Lizards: The Evolution of Habitat Specialists." Terra 28 (1989): 29–34.
Bezy, R. L., and J. L. Camarillo R. "Systematics of Xantusiid Lizards of the Genus Lepidophyma." Contributions in Science 493 (2002): 1–41.
Brattstrom, B. H. "The Number of Young of Xantusia." Herpetologica 7 (1951): 143–144. ——. "The Food of the Night Lizards, Genus Xantusia." Copeia (1952): 168–172.
Crother, B. I. "Cricosaura, C. typica." Catalogue of American Amphibians and Reptiles 443 (1988): 1–3.
Crother, B. I., M. M. Miyamoto, and W. F. Presch. "Phylogeny and Biogeography of the Lizard Family Xantusiidae." Systematic Zoology 35 (1986): 37–45. de Armas, L. F., A. Rams, and A. Torres. "Primeras observaciones sobre la alimentacion de Cricosaura typica (Sauria: Xantusiidae) en condiciones naturales." Miscellaneous Zoology 32 (1987): 1–2.
Estrada, A. R., and L. F. de Armas. "Apuntos ecologicos sobre Cricosaura typica (Sauria: Xantusiidae) de Cuba." Caribbean Journal of Science 34 (1998): 160–162.
Fellers, G. M., and C. A. Drost. "Xantusia riversiana." Catalogue of American Amphibians and Reptiles 518 (1991): 1–4. ——. "Ecology of the Island Night Lizard, Xantusia riversiana, on Santa Barbara Island, California." Herpetological Monographs 5 (1991): 28–78.
Hass, C. A., and S. B. Hedges. "Karyotype of the Cuban Lizard Cricosaura typica and Its Implication for Xantusiid Phylogeny." Copeia (1992): 563–565.
Hedges, S. B., R. L. Bezy, and L. R. Maxson. "Phylogenetic Relationships and Biogeography of Xantusiid Lizards, Inferred from Mitochondrial DNA Sequences." Molecular Biology and Evolution 8 (1991): 767–780.
Lee, J. C. "The Diel Activity Cycle of the Lizard, Xantusia henshawi." Copeia (1974): 934–940. ——. "The Autecology of Xantusia henshawi (Sauria: Xantusiidae)." Transactions of the San Diego Society of Natural History 17 (1975): 259–278. ——. "Xantusia henshawi." Catalogue of American Amphibians and Reptiles 189 (1976): 1–2.
Mautz, W. J. "The Metabolism of Reclusive Lizards, the Xantusiidae." Copeia (1979): 577–584. ——. "Thermal Biology and Microhabitats of Xantusiid Lizards: Herpetology of the North American Deserts, Proceedings of a Symposium. Southwest Herpetologists Society Special Publication 5 (1994): 227–238.
Mautz, W. J., and T. J. Case. "A Diurnal Activity Cycle in the Granite Night Lizard, Xantusia henshawi." Copeia (1974): 243–251.
Petzold, H.-G. "Cricosaura typica Gundlach & Peters, eine herpetologische Kostbarkeit aus Kuba." Die Aquarien und Terrarien Zeitschrift 22 (1969): 82–85.
Telford, S. R., and H. W. Campbell. "Ecological Observations on an All Female Population of the Lizard Lepidophyma flavimaculatum (Xantusiidae) in Panama." Copeia (1970): 379–381.
Zweifel, R. G., and C. H. Lowe. "The Ecology of a Population of Xantusia vigilis, the Desert Night Lizard." American Museum Novitates 2247 (1966): 1–57.
[Article by: Robert L. Bezy, PhD; L. Lee Grismer, PhD]
