CLASS Amphibia: amphibians. Ectotherms (cold-blooded). Breathing through lungs, gills or skin. Moist skin devoid of scales, with mucous glands. Development through larval stages.

ORDER Gymnophiona: caecilians. Apods (without limbs). Eel-like body. Short tail or absent. 95-285 vertebrae. Tropical. 6 families and some 160 species.

FAMILY Caeciliidae: advanced apods. Widely extended throughout the tropics. 23 genera, 88 species.
FAMILY Ichthyophiidae: primitive apods. Tropical Asia. 2 genera, 36 species.
FAMILY Rhinatrematidae: primitive apods. North of South America. 2 genera, 9 species.
FAMILY Scolocomorphidae: advanced apods. Equatorial, West and East Africa. 2 genera, 5 species.
FAMILY Typhlonectidae: advanced apods. South America. 4 genera, 12 species.
FAMILY Uraeotyphlidae: intermediate apods. India. 1 genus, 4 species.

SUPERORDER Batrachia: anurans and urodelans.

ORDER Anura (Salientia): anurans (frogs and toads). No tail or scales. Two pairs of limbs. Head and body fused. Lungs. 6-10 vertebrae. Cosmopolitan, but mostly tropical. 26 families and some 3,800 species.

SUBORDER Archeobatrachia: primitive frogs. Free ribs. 4 families.

FAMILY Ascaphidae: only 1 species, Ascaphus truei, the only tailed frog. Northwestern USA and southwestern Canada.
FAMILY Bombinatoridae: fire-bellied toads. Asia and Europe. 2 genera, Bombina and Barbourula, 8 species.
FAMILY Discoglossidae: discoglossids (disc-shaped tongue, not protractile). Round pupils. 2 genera, Alytes (midwife toads, Europe) and Discoglossus (Europe and northwestern Africa).
FAMILY Leiopelmatidae: New Zealand. 4 species.

SUBORDER Mesobatrachia: intermediate frogs. 4 families.

SUPERFAMILY Pelobatoidea: vertical pupils. Aquatic, free life tadpoles.

FAMILY Pelobatidae: spadefoot toads. Asia, Europe, America and northern Africa. 9 genera, 90 species.
FAMILY Pelodytidae: parsley frogs. Terrestrial. Europe. 1 genus, 2 species.

SUPERFAMILY Pipoidea

FAMILY Pipidae: tongueless dumb frogs. Very aquatic. 4 genera, 27 species.

SUBFAMILY Pipinae: South America and Africa. 2 genera, Pipa (Surinam toad) and Hymenochirus (dwarf clawed frog).
SUBFAMILY Xenopodinae: Africa. 2 genera, Xenopus (clawed frogs) and Silurana.

FAMILY Rhinophrynidae: Central America. 1 species, Rhinophrynus dorsalis (Mexican burrowing toad).

SUBORDER Neobatrachia: advanced frogs. More than 3,600 species, 95% of all living frogs. 18 families.

SUPERFAMILY Bufonoidea (Hyloidea): non-ranoid neobatrachians. 11 families.

FAMILY Allophrynidae: 1 species, Allophryne ruthveni. Guyana.
FAMILY Brachycephalidae: gold frogs. Psyllophryne didactyla, measuring only 9.8 mm, is the world's smallest four-legged animal. Southern Brazil Atlantic coast. 3 species.
FAMILY Bufonidae: true toads and harlequin frogs. Distributed all around the world except Australasia and Madagascar. 26 genera, 360 species.
FAMILY Centrolenidae: glass frogs (skin almost transparent). Central and South America. 3 genera, 75 species.
FAMILY Heleophrynidae: ghost frogs. Southern tip of Africa. 1 genus (Heleophryne), 4 species.
FAMILY Hylidae: tree frogs. 40 genera, 680 species.

SUBFAMILY Hemiphractinae: South America and Panama.
SUBFAMILY Hylinae: America, Europe, Asia and Africa.
SUBFAMILY Pelodryadinae: Australia and New Guinea.
SUBFAMILY Phyllomedusinae: leaf frogs. Central and South America. Includes the red-eyed tree frog.

FAMILY Leptodactylidae: American frogs. Central and South America, West Indies. 52 genera, 800 species.

SUBFAMILY Ceratophryinae: 2 aggressive and carnivore genera, one terrestrial (Ceratophrys) and the other one aquatic (Lepidobatrachus).
SUBFAMILY Eleutherodactylinae (Telmatobiinae): includes the genus Eleutherodactylus, with more than 400 species.
SUBFAMILY Hylodinae: 3 genera.
SUBFAMILY Leptodactylinae: lay their eggs on foam nests.

FAMILY Myobatrachidae: generally terrestrial or dwellers of wet zones. Australia and New Guinea. 20 genera, 100 species.
FAMILY Pseudidae: paradox frogs, tadpoles are bigger than adults. South America. 2 genera, 4 species.
FAMILY Rhinodermatidae: Darwin's frogs. They incubate their eggs inside their mouth. Southern tip of South America. 1 genus, 2 species.
FAMILY Sooglossidae: Seychelles frogs. 2 genera, 3 species.

SUPERFAMILY Microhyloidea: 2 families.

FAMILY Arthroleptidae: squeakers. Subsaharan Africa. Includes the "hairy frog", Trichobatrachus robustus. 8 genera, 70 species.

SUBFAMILY Arthroleptinae: 3 genera.
SUBFAMILY Astylosterninae: vertical pupils. 5 genera.

FAMILY Microhylidae: microhylid toads (narrow-mouthed). Worldwide, mostly in tropical regions. 65 genera, 300 species.

SUPERFAMILY Ranoidea: 5 families.

FAMILY Dendrobatidae: dart-poison frogs, brightly coloured. Central and South America. 6 genera, 130 species.
FAMILY Hemiotidae: shovel-snouted frogs. They use it for burrowing. Subsaharan Africa. 1 genus, 8 species.
FAMILY Hyperoliidae: reed frogs. Africa, Madagascar and Seychelles. 16 genera, 200 species.

SUBFAMILY Hyperoliinae
SUBFAMILY Kassininae
SUBFAMILY Leptopelinae

FAMILY Ranidae: "true" frogs. Worldwide. 38 genera, 650 species. Two thirds belong to the genus Rana.

SUBFAMILY Raninae
SUBFAMILY Petropedetinae
SUBFAMILY Mantellinae

FAMILY Rhacophoridae: Old World tree frogs. Africa and Asia. Includes the Asian gliding frog Rhacophorus nigromaculatus. 10 genera, 200 species.

SUBFAMILY Philautinae
SUBFAMILY Rhacophorinae

ORDER Caudata (Urodela): urodelans (salamanders and newts). No scales. In general, two pairs of similar limbs. Head, body and tail. 10-60 vertebrae. Mostly holarctic. 10 families and some 380 species.

SUPERFAMILY Cryptobranchoidea: primitive salamanders, with external fertilization. Angular and prearticular bones in lower jaw are separated in the adult.

FAMILY Cryptobranchidae: cryptobranchids. Giant salamanders, up to 1.8 m in length, permanently aquatic. USA, China and Japan. 2 genera, 3 species.
FAMILY Hynobiidae: hynobids. Asia. 9 genera, 35 species.

SUPERFAMILY Salamandroidea: higher salamanders. Angular and prearticular bones fused in the lower jaw. Internal fertilization.

FAMILY Ambystomatidae: mole salamanders, axolotls. North America. 2 species have only females. 2 genera, 34 species.
FAMILY Amphiumidae: amphiumas. Referred to as Congo eels, but they are not eels nor they live in Congo but in the USA. Long (up to more than 1 m), with very reduced limbs. 1 genus (Amphiuma), 3 species.
FAMILY Dicamptodontidae: Pacific giant salamanders. Axolotls with a bone in the lacrimal that is missing in Ambystomatidae. USA. 1 genus, 4 species.
FAMILY Plethodontidae: lungless salamanders. They breathe through moist skin. Nasolabial grooves for chemoreception. America, a few European species. 30 genera, 250 species.

SUBFAMILY Desmognathinae
SUBFAMILY Plethodontinae

TRIBE Bolitoglossini
TRIBE Hemidactyliini
TRIBE Plethodontini

FAMILY Proteidae: proteids and mudpuppies or waterdogs (they were believed to bark). Metamorphosis is absent. Europe and the USA. 2 genera, 6 species.
FAMILY Rhyacotritonidae: Olympic salamanders or torrent salamanders. USA. 1 genus (Rhyacotriton), 4 species.
FAMILY Salamandridae: newts (aquatic; 10 genera; Europe, Asia, Africa and America) and "true salamanders" (terrestrial; 4 genera; Europe, Africa and Asia). 14 genera, 60 species.

SUBORDER Sirenoidea

FAMILY Sirenidae: sirens. Metamorphosis is absent. Eel-like body without hindlimbs. USA and Mexico. The biggest ones measure up to 1 m. Probably external fertilization. 2 genera, 3 species.