The tailless amphibians we commonly refer to as frogs and toads belong to the order Anura. This is most diverse order in the class Amphibia with more than 6000 species distributed throughout much of the world (with the exceptions of polar regions and some extreme deserts such as the Sahara of northwestern Africa). The highest diversity of anurans are found in tropical humid forest regions. The Neotropics are especially diverse, and new species are continually being described, especially from South America. Anurans have several differences from caudates and caecilians, among them are the strong and long hind-limbs that facilitate jumping, and their ability to make vocalizations in most species. Costa Rica has 143 species of anurans. The most diverse family of anurans in Costa Rica is Hylidae, with 43 species among 15 genera.