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a family of tailless amphibians. There are two genera, Pipa and Xenopus. The former genus has five species. The largest of these amphibians reach 20 cm long, with the females noticeably larger than the males. The head is broad, the snout pointed, the eyes lidless, and the body flattened. The forelegs have four long digits without swimming webs. The hind legs are considerably thicker and longer than the forelegs, and their five digits are webbed.
The amphibians are distributed in the tropics of South America, from Panama and Venezuela southward to Peru and southern Brazil. They live in or near water. Reproduction is unique and has been most studied in the Surinam toad (P. pi-pa). During mating, the female everts the cloaca on her back, which consists of a saclike ovipositor. The male presses his abdomen on the ovipositor, squeezing out as many as 114 large yolk-rich eggs. The eggs fall into the pits on the female’s back (10–15 mm deep), which are covered with a cutaneous coating formed from the egg membranes. Development of the eggs and formation of the tadpoles occur in the pits. After 80 to 85 days, fully formed frogs emerge and the female molts.
I. S. DAREVSKII