True frogs conquered more land than any frog family
Ranidae, the true frogs, claim the widest distribution of any frog family, thriving on most continents with smooth moist skin, strong legs, and big webs. Sizes span tiny species to giants; most lay eggs in water and pass through tadpoles, though exceptions exist as in other frog clans.
No other frog family covers as much ground. True frogs live on every continent except Antarctica, from Europe, Africa and Madagascar to Asia, North America and the northern part of South America, with the Asian range stretching through the East Indies to New Guinea. A single species, the Australian wood frog, has crept into Australia's far north. Most have smooth, damp skin, powerful hind legs and heavily webbed feet, and they range from small animals like the North American wood frog to hefty giants. Many stay in or near water, laying eggs there that hatch into tadpoles, but some climb trees, and a few are among the rare amphibians able to tolerate brackish water.
Their origins are debated. An older view held that the family arose on the drifting Indian landmass during the Cretaceous and spread only after India struck Asia in the late Eocene. Newer work argues the reverse: the family began in Eurasia, and its Indian relatives reached the subcontinent from there during the Paleogene. Their nearest kin may be the Indian Nyctibatrachidae, split off in the early Eocene, or the Dicroglossidae. Either way, they left Asia near the end of the Eocene and had reached every habitable continent by the early Miocene.
Classification remains messy. Several former subfamilies, including the Mantellidae and Dicroglossidae, now stand as families of their own, leaving only the Raninae, and the once-sprawling genus Rana has been sharply pared back. Staurois looks like an ancient early branch, while Babina, Hylarana, Pelophylax and several allies form a loose, probably unnatural cluster. In 2023 Amphibian Species of the World provisionally folded eight genera into Hylarana, a move AmphibiaWeb does not accept, and some species still sit unplaced. North American true frogs commonly host the parasitic fluke Halipegus eccentricus.
Source: Ranidae
