The head is bluish with red to orange colors around the eyes, yellow neck with blue spots and streaks.

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.

Petrosaurus thalassinus is most often found in the immediate vicinity of rocky canyons, boulder-strewn hillsides and arroyo bottoms and sea-side cliffs.

It is found in the Sierra la Laguna (and its associated ranges) and Sierra la Trinidad of the Cape region of Baja California Sur, as well as on Islas Espiritu Santo and Partida Sur in the Gulf.