What is "earless lizard"

n. any of several slender lizards without external ear openings: of plains of western United States and Mexico

Earless lizards are two genera of small lizards native to the semi-arid and grassland habitats of the southwestern United States and Mexico. The genus Cophosaurus and the genus Holbrookia are both characterized by having no external ear openings, presumably to prevent sand from entering the body as they dig.