ABSTRACT
Lepidosaurs are the largest group of living tetrapods outside of birds. They include the approximately 5,000 species of lizards and 3,000 species of snakes (which together comprise the squamate reptiles), plus the two species of Tuatara (Sphenodon).
Lizards and snakes, the best-known squamates, are a timeless study in ecological diversity. As with arid lands elsewhere in the world, Southern California hosts a diverse assemblage: 10 families and 37 species of lizards and 5 families and 35 species of snakes. Lizards and snakes are popularly thought of as discrete from one another, and snakes indeed have numerous characteristics of their own, as for example the vertebral column and the highly modified skull and lower jaw. However, snakes are embedded within lizards phylogenetically and should not be construed as evolutionarily distant relatives.
Many squamates are visually oriented, especially the Iguania and Gekkota, and some arboreal snakes. Less visually oriented squamates rely on olfactory cues by collecting chemical signals with their tongue.
Squamates are ectotherms that convert food energy to other needs when they are active and can sustain long periods of no or minimal energy intake and expenditure when they are not. Ectothermy is energetically inexpensive because there is no metabolic requirement for a constant body temperature.
Squamate reproduction is varied and complex with respect to courtship, embryogenesis (oviparity, viviparity, and parthenogenesis), fecundity, and parental care.
