Lissamphibia

Lissamphibia is the crown group of living amphibians, comprising three orders: Anura (frogs and toads), Caudata/Urodela (salamanders and newts), and Gymnophiona (caecilians). The group represents all extant amphibians and is distributed worldwide except Antarctica. The term Lissamphibia means "smooth amphibians," reflecting their typically moist, permeable skin.

Common characteristics include moist, permeable skin used in respiration and water absorption, a life cycle that typically involves an aquatic larval stage with metamorphosis to a more terrestrial adult, and a specialized dentition known as pedicellate teeth. Members range from aquatic to terrestrial species and display a variety of reproductive strategies, including eggs laid in water and direct development in some frogs and salamanders.

Morphology varies by order: Anura lack tails as adults and often have long hind limbs adapted for jumping; Caudata (salamanders and newts) retain tails and have elongated bodies with four legs; Gymnophiona are legless, burrowing, and resemble worms or snakes.

Life histories vary: most species lay eggs in moist environments or water; offspring may begin life as free-swimming larvae, or develop directly into miniature adults. Some caecilians are viviparous with embryos nourished by uterine secretions; paedomorphosis occurs in several salamander species, retaining larval traits into adulthood.

Conservation: Lissamphibians are sensitive indicators of environmental health and are threatened by habitat loss, pollution, climate change, and disease, notably chytridiomycosis. With thousands of species, the group is increasingly the focus of conservation and research attention.