RACERUNNER

also called Whiptail, any of about 50 species of lizards that constitute the genus Cnemidophorus of the family Teiidae. They are the only genus of the family occurring in the United States, where they are common; their range extends southward to Argentina. Their size varies from 20 to more than 40 cm (8 to 16 inches). Racerunners may be diversely marked, even within a species, being yellow-striped, spotted, or both, on a brown or black background. They generally prefer open country, and some inhabit deserts. Forest types are found in clearings and on open trails. The genus is of great interest because of the existence of sexual as well as parthenogenetic species and because of species that have three and four sets of chromosomes rather than the usual two.