The Baja blue rock lizard (Petrosaurus thalassinus) is a 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...

 of large, diurnal phrynosomatid

Phrynosomatidae

Phrynosomatidae is a diverse family of lizards, found from Panama to the extreme south of Canada. Many members of the group are adapted to life in hot, sandy deserts, although the spiny lizards prefer rocky deserts or even relatively moist forest edges, and the short-horned lizard lives in prairie...

 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...

.

Description

It reaches up to 45 cm (17¾ inches) long including the tail, and has a flattened body with small, smooth, granular scales and slightly keeled scales near the tail. The head is bluish with red to orange colors around the eyes, yellow neck with blue spots and streaks. The back of the tail is gray blue with darker cross bars. The coloration intensifies during the breeding season in both sexes.

Behavior

It prefers temperatures in excess of 90°F and basks in direct sunlight on desert rocks. A very wary species, its flattened body allows it to quickly retreat into rock crevices to escape predators as well as inclement weather conditions. When threatened, it can extend a skin flap along its throat. Like many lizards, it is able to drop its tail when caught.

Diet

It feeds on various insects, small lizards, blossoms, leaves, seeds, and small fruit. Occasional incidents of cannibalism on smaller individuals have been observed.

Taxonomy

Two subspecies are recognized within P. thalassinus; P. t. thalassinus inhabits the Cape region, and P. t. repens ranges north of the isthmus of La Paz. P. t. repens differs by having a thin, black, postorbital stripe; one row of scales between the nasal and the supralabials

Supralabial scales

In reptiles, the supralabial scales, also called upper-labials, are those scales that border the mouth opening along the upper jaw. They do not include the median scale . The term labial originates from Labium , which refers to any lip-like structure...

 as opposed to two, and reaching a maximum snout to vent

Cloaca

In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

 length of 111 mm as opposed to 162 mm. Genetic studies indicate that all populations within P. thalassinus, including the two subspecies show only low levels of genetic divergence

Genetic divergence

Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes through time, often after the populations have become reproductively isolated for some period of time...

, indicative of high rates of gene flow

Gene flow

In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...

. In contrast, P. thalassinus is strongly differentiated from its sister species P. mearnsi.

Life History

Breeding takes place in the spring. 20 to 30 eggs are laid in late spring and summer, and hatchlings appear after 85 to 88 days in summer and early fall. Sexual maturity is reached after about 2 years with a life expectancy of 20 years.

Habitat

P. thalassinus is most often found in the immediate vicinity of rocky canyons, boulder-strewn hillsides and arroyo bottoms and sea-side cliffs. These lizards appear to be particularly common on rocks near large trees or other vegetation, and rarely seen in areas where vegetation is non-existent.

Geographic range

It is found in the Sierra la Laguna (and its associated ranges) and Sierra la Trinidad of the Cape region of 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...

Sur, as well as on Islas Espiritu Santo and Partida Sur in the Gulf. Elevational distribution from sea level to 2,020 meters in the Sierra la Laguna.

Conservation

This species is locally abundant and occurs on several protected islands. It is currently in no need of special protection. However, its small range may make it vulnerable to disturbance.