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By Richard M. Lehtenin
The thirty species in the family Pipidae are found in tropical South America (Pipa) and sub-Saharan Africa (four other genera).
These frogs are exclusively aquatic and have numerous morphological modifications befitting their habitat. For example, the feet are completely webbed and a lateral line system is present. In addition, pipids possess highly modified ears and vocal structures for producing and receiving sound underwater. Pipids are also unique among known frogs in not having a tongue and possessing "claws" on one or more toes (not present in Pipa).
Pipids are relatively primitive frogs, most closely related to the Rhinophrynidae. Some primitive characteristics of pipids include inguinal amplexus and opisthocoelous vertebrae, however, many aspects of pipid morphology are seemingly derived for an aquatic lifestyle.
Some species of pipids have an elaborate courtship ritual that involves a variety of underwater acrobatics. In Pipa, the sticky eggs are taken by the male after deposition and pressed into the back of the female. The skin swells and envelopes the eggs, which remain embedded in the females back until hatching. In the other genera, eggs are deposited in ponds or other stagnant water bodies and the larvae are filter-feeding (with the exception of Hymenochirus, which have carnivorous larvae).
The fossil record for pipids is relatively good with twelve extinct species known. Six of these are placed in the extant genus Xenopus, the remainder in extinct genera. These fossils are known from Africa, South America, and Middle East back to the Lower Cretaceous.
Little is known about the conservation status of pipids, but amphibians in general are thought to be sensitive to changes in their environment (see AmphibiaWeb's 
declining amphibians page).
Duellman, W.M. and L. Trueb. 1984. Biology of the Amphibians.
Pough, F.H., R.M Andrews, J.E. Cadle, M.L. Crump, A.H. Savitzsky, K.D. Wells. 1998. Herpetology. Prentice-Hall, Upper Saddle River, NJ.
Frost, Darrel R. 2002. Amphibian Species of the World: an online reference.
V2.21 (15 July 2002). Electronic database available at http://research.amnh.org/herpetology/amphibia/index.html.
Contributors
Richard M. Lehtenin (author).
