Ranoids

Microhylidae. The narrow-mouthed frogs represent an enormously diverse and speciose ranoid family (68 genera, 361 species) found worldwide in temperate and tropical locations. The group is characterized by a derived tadpole that lacks either oral denticles or a beak. The taxic diversity of the family is primarily found from tropical southeastern Asia to Australia, but other radiations are found in sub-Saharan Africa and the Americas.

Dendrobatidae. The dart-poison frogs (9 genera, 201 species) are an easily diagnosed group of small terrestrial frogs (except for one species that is aquatic) found in southern Central America and tropical South America. The common name is not particularly apt, as only a very few species were ever used for dart poison; most of the species are not particularly brightly colored or toxic, although some are highly desired in the pet trade for those reasons. The consideration of the dendrobatids within the ranoids is a continuing controversy, but the published evidence currently supports its placement here. Eggs are laid in terrestrial or arboreal locations, and either the males or females (depending on species) carry the tadpoles on their back to water.

Hemisotidae. The pig-snouted frogs are a small group (one genus, eight species) of ranoid frogs found in tropical and subtropical sub-Saharan Africa and of uncertain affinities. They burrow head-first, which is unusual for frogs, and lay eggs in subterranean nests that release the aquatic larvae when the nest floods.

"Arthroleptidae." The squeakers (7 genera, 61 species) are a composite of two groups of sub-Saharan African ranoid frogs that together have been posited to be para-phyletic to the African treefrogs, the Hyper-oliidae. Direct development has been reported in most of the members of one of these groups, the Arthroleptinae, but the other group, the Astylosterninae, have aquatic eggs and larvae.

Petropedetidae. The Petropedetidae (13 genera, 101 species) are a group of sub-Saha-ran African ranoid frogs that are poorly studied and of dubious monophyly. Direct development has been reported in some species, but most lay aquatic eggs on vegetation overhanging water or in water and have aquatic larvae.

"Ranidae." The Ranidae (21 genera, 605 species) are a catch-all of ranoid frogs that are not members of the other ranoid families. The group is cosmopolitan, with a number of relatively closely related species (Rana) being found in Europe, North Africa, Eurasia, and temperate and tropical North America, south to tropical South America. The taxic diversity of the ranids is predominantly in tropical Asia, where the diversity of morphology and ecology is very large, and in sub-Saharan Africa. Arboreal tadpoles have been reported, although most species have aquatic eggs and larvae. In one group found in the Philippines and Fiji, direct development is reported.

Hyperoliidae. The African treefrogs (19 genera, 240 species) are found in sub-Saharan Africa and Madagascar. Ecologically they vary from arboreal to terrestrial. Their systematics are very poorly understood, and clearly there are many undescribed species. There are a diversity of reproductive types, with eggs being laid in the water, in arboreal foam nests, and on leaves above the water.

Rhacophoridae. The Asiatic treefrogs (12 genera, 430 species) are found in tropical and subtropical Asia, with one genus (Chiroman-tis) in sub-Saharan Africa and another radiation in Madagascar. It is reasonably clear that this taxon renders the "Ranidae" paraphyletic, although considerable work remains to be done. Most species have aquatic eggs and larvae, although a few lay their eggs in arboreal locations and some have an abbreviated non-feeding larval stage.

—Darrel Frost

See also: Adaptive Radiation; Classification, Biological; Evolution; Evolutionary Biodiversity; Geological Time Scale; Linnaean Hierarchy; Phylogeny; Species; Zoology

Bibliography

Duellman, William E., and L. Alice Trueb. 1986. Biology of Amphibians. NY: McGraw-Hill; Frost, Darrel R. 1985. Amphibian Species of the World. Lawrence, KS: Allen Press, Association of Systematics Collections; Frost, Darrel R. 2001. Amphibian Species of the World: An Online Resource. http://research.amnh.org; Halli-day, Tim, and Kraig Adler, eds. 1986. The Encyclopedia of Reptiles and Amphibia. New York: Facts on File; Laurent, Raymond F. 1986. "Sous classe des lissam-phibiens (Lissamphibia): Systématique." In Traité de Zoologie. Anatomie, Systématique, Biologie. Amphibians, vol. 11, edited by P. P. Grassé, pp. 594-797. Paris: Mas-son; McDiarmid, Roy W., and Ronn Altig, eds. 1999. Tadpoles: The Biology of Anuran Larvae. Chicago: University of Chicago Press; Petranka, James. 1998. Salamanders of the United States and Canada. Washington, DC: Smithsonian Institution Press; Thorn, Robert, and Jean Rafaëlli. 2001. Les salamandres de l'Ancien Monde. Paris: Societe Nouvelle des Editions Boubee.

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