Night lizard

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Night lizards

Xantusia vigilis

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Sauria
Family:	Xantusiidae

Subfamilies

See text.

Night lizards (family name Xantusiidae) are a group of very small, viviparous (live-bearing) lizards, averaging from less than 4 cm to over 12 cm long. It has only three genera, with approximately 23 living species. The genera are divided by geographic range: Xantusia in southwestern North America and Baja California, Cricosaura in Cuba, and Lepidophyma, the most populous night lizard genus, in Central America.

Night lizards were originally mistaken to be nocturnal because of their secretive lifestyle, but they are in fact strictly diurnal. Physically, night lizards are characterized by relatively flat bodies and heads. Their heads are covered by large, smooth plates, while their bodies have rougher, granular skin. Their eyes, like those of snakes, are covered by immoveable, transparent membranes that function as eyelids. They feed on insects and sometimes plants.

Contrary to the reproductive strategies of most small lizards, night lizards tend to have very low reproductive rates, with several species giving birth to only one or two offspring. They generally take several years to reach sexual maturity. However, the very limited lifestyle of night lizards has contributed to a high life expectancy. Night lizards have evolved to live in very narrow environmental niches—"microhabitat specialization"—such as rock crevices or damp logs, and may spend their entire life under the same cover.