Night lizards (

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Xantusiidae) are a group of small

scincomorph Scincomorpha is an infraorder and clade of lizards including skinks (Scincidae) and their close relatives. These include the living families Cordylidae (girdled lizards), Gerrhosauridae (plated lizards), and Xantusiidae (night lizards), as wel ...

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s, averaging from less than to over

snout–vent length Snout–vent length (SVL) is a morphometric measurement taken in herpetology from the tip of the snout to the most posterior opening of the cloacal slit (vent)."direct line distance from tip of snout to posterior margin of vent" It is the most c ...

. 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 m ...

(live-bearing), with the exception of those in the genus '' Cricosaura''. The family has only three living

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

, 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 ''Xantusia'' is one of three genera of night lizards (family '' Xantusiidae''). Species of ''Xantusia'' are small to medium-sized, viviparous (live-bearing) lizards found in the U.S. Southwest and in northern Mexico. Taxonomy and etymology Th ...

'' in southwestern

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

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 ''Lepidophyma'' is a genus of lizards, commonly called tropical night lizards. The genus ''Lepidophyma'' (Greek for "warty scales") is one of three genera of night lizards (family Xantusiidae), which are a group of viviparous (live-bearing) l ...

'', 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 ''Catactegenys'' is an extinct genus of xantusiid lizard from the Late Cretaceous of Texas. The type species, ''Catactegenys solaster'', was named in 2013 from the late-Campanian-age Aguja Formation in Brewster County. The genus name means "br ...

'', '' Palepidophyma'', '' Palaeoxantusia''.

Biology

Night lizards were originally thought to be

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

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 t ...

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 Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joi ...

, 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 Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

. 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 definitio ...

. 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