High Quality Content by WIKIPEDIA articles! Atelopus, commonly known as harlequin frogs, is a large genus of true toads from Central and South America, ranging as far north as Costa Rica and as far south as Bolivia. Atelopus are small, generally brightly colored and diurnal. Most species are associated with mid- to high-elevation streams. This genus has been greatly affected by amphibian declines, and many species are now considered endangered, while others already are extinct. The cause of these declines primarily appears to be the chytrid fungus Batrachochytrium dendrobatidis.