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Bufonids are the true toads, although some are not particularly toadlike. The large genus Bufo has over 200 species and is naturally cosmopolitan except for Australia. The other genera are distributed in three tropical areas: South America, Africa, and southeast Asia. Some of these other genera are clearly derived from Bufo, but others belong to a major evolutionary lineage that is distinct from Bufo and its allies.
Bufonids range in size from 20 to more than 200 mm. No bufonids have teeth, although the absence of teeth occurs sporadically in other frog groups. Also, many bufonids (but not all) have a Bidder's organ, which is a mass of gonadal tissue in males that has the appearance of an immature testis. If the testis of a male is surgically removed, the Bidder's organ will enlarge and differentiate into a functional ovary.
Most toads of the genus Bufo are dull. However, Bufo periglenes is brightly colored and exhibits extreme color dimorphism between males and females. This rare toad lives in the cool wind-swept cloud forests of Costa Rica near Monteverde. It has not been observed in several years and may be extinct.
Species of the genus Atelopus, also called Harlequin Frogs, are brightly colored. Atelopus zeteki from Panama have skin toxins (Brown et al. 1977). Bufo spinulosus is among the highest ranging amphibians; it is known from about 5000 m elevation in the Andes of South America.