Night lizards are a group of very small, viviparous

Vivipary

Vivipary has two different meanings. In animals, it means development of the embryo inside the body of the mother, eventually leading to live birth, as opposed to laying eggs...

 (live-bearing) lizard

Lizard

Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

s, averaging from less than 4 cm to over 12 cm long. The family has only three genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, with approximately 23 living species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

. The genera are divided by geographic range: Xantusia

Xantusia

Xantusia is one of three genera of night lizards . Species of Xantusia are small to medium-sized, viviparous lizards found in the U.S...

in southwestern North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 and Baja California

Baja California

Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...

, Cricosaura in Cuba

Cuba

The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...

, and Lepidophyma

Lepidophyma

Tropical night lizards compose one of three genera of night lizards , which are a group of viviparous lizards. There are 19 tropical night lizard species, making it the most populous night lizard genus...

, the most populous night lizard genus, in Central America

Central America

Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

.

Biology

Night lizards were originally thought to be nocturnal because of their secretive lifestyle, but they are in fact strictly diurnal

Diurnal animal

Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...

. Night lizards have evolved

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 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.

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

Insectivore

An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....

 and sometimes plants

Herbivore

Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

.

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, after a gestation period of about three months. They generally take several years to reach sexual maturity

Sexual maturity

Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...

. However, the very limited lifestyle of night lizards has contributed to a high life expectancy.

Genera

FAMILY XANTUSIIDAE

• Subfamily Cricosaurinae
  • Genus Cricosaura - Cuban night lizard
• Subfamily Xantusiinae
  • Genus Lepidophyma
    Lepidophyma
    Tropical night lizards compose one of three genera of night lizards , which are a group of viviparous lizards. There are 19 tropical night lizard species, making it the most populous night lizard genus...
    
    - Tropical night lizards
  • Genus Xantusia
    Xantusia
    Xantusia is one of three genera of night lizards . Species of Xantusia are small to medium-sized, viviparous lizards found in the U.S...
    
    - Typical night lizards

External links

• xantusiidae