Night lizards

The Xantusiidae, named for 19th Century Smithsonian officer and naturalist John Xantus (1825-1894), is a family of small lizards (maximum length 9 inches) found in the extreme southwestern United States, Mexico, Central America, and Cuba. They are colloquially known as night lizards or bark lizards. All species lack moveable eyelids, posses ear openings, four limbs with five digits, and rectangular ventral scales arranged in regular rows. Head scales are typically large, while body scales are tiny and granular. The Central American species may possess enlarged, pebble-like tubercles, giving them a close but superficial resemblance to the Xenosauridae.

Night lizards, with their arboreal habits, large lidless eyes and granular skins, may be confused with geckos. However, night lizards lack adhesive toe pads, possess enlarged upper head scales, and have belly scales in longitudinal rows. The tongue is broad and flat. 

Night lizards are nocturnal or cave-dwelling species not seen in broad daylight. Their flattened bodies allow them to secrete themselves under cracks in stone, making collection difficult. The tails are fragile, and autotomy is present.