Night lizards (
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Xantusiidae) are a group of small
scincomorph lizards, averaging from less than to over
snout–vent length. Most species are
viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
(live-bearing), with the exception of those in the genus ''
Cricosaura''. The family has only three living
genera, with approximately 34
living
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
. The genera are divided by geographic range: ''
Xantusia'' in southwestern
North America and
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
, ''
Cricosaura'' in
Cuba
Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...
, and ''
Lepidophyma'', the most populous night lizard genus, in
Central America
Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...
. Three fossil genera are also known: ''
Catactegenys'', ''
Palepidophyma'', ''
Palaeoxantusia''.
Biology
Night lizards were originally thought to be
nocturnal because of their secretive lifestyle, but they are at least in some cases
diurnal. Night lizards have
evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
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
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...
and sometimes
plants
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude ...
.
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 is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definit ...
. However, the covert lifestyle of night lizards has contributed to a high life expectancy.
References
External links
Xantusiidae
{{Authority control
Taxa named by Spencer Fullerton Baird