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Introduction to Amphibians

By Brent R. Whitaker, MS, DVM, Vice President of Biological Programs, National Aquarium

The word amphibian comes from the Greek word for “double-life,” referring to the fact that amphibians start life in water breathing through gills before maturing into lung-breathing land animals, although most never stray too far from water. The class Amphibia is composed of only 3 orders. Anura, which refers to tailless amphibians, includes frogs and toads (see Table: Similarities and Differences Between Frogs and Toads). This is the largest order with more than 3,500 species. Caudata refers to amphibians with tails—salamanders, newts, and sirens—and has about 375 species (see Table: Some Common Salamanders and Newts). The Gymnophiona order is made up of caecilians, legless, tailless amphibians that spend most of their time burrowing. It has about 160 species.

There are many different types of amphibians, including frogs, toads, salamanders, and newts.

Similarities and Differences Between Frogs and Toads






Both hatch from eggs

Lay eggs in clusters

Lay eggs in chains

Young have gills

Teeth in upper jaw

Have no teeth

Adults have lungs

Moist, smooth skin

Dry, lumpy skin

Young live in water



Bulging eyes

Eyes do not protrude

Some Common Salamanders and Newts




Tiger salamander (Ambystoma tigrinum)

Western-central Canada south to Mexico and east and north to Long Island New York; sandy soils; common as pets

Varies according to type; can be up to 12 inches (31 centimeters)

Axolotl salamander (Ambystoma mexicanum)

Native to Xochimilco and Chalco lakes, Mexico City; strictly aquatic; common as pets

8 to 11 inches (20 to 28 centimeters)

Marbled salamander (Ambystoma opacum)

From southern New England, west to parts of Texas, Illinois, Oklahoma, and south to north Florida; variety of habitats

Up to 4.25 inches (11 centimeters) in length

Redback salamander (Plethodon cynereus)

Canada, northern United States to Midwest; woodland

Small: 2.6 to 4.9 inches (6.5 to 12.5 centimeters)

Seal salamander (Desmognathus monticola)

Southwestern Pennsylvania, to Georgia and Alabama; streams, ravines, and similar habitat

Size varies

Blackbelly and shovelnose salamanders (Desmognathus quadramaculatus, D. marmoratus)

Appalachia; springs and streams

Medium to large

Two-lined and Junaluska salamanders (Eurycea bislineata, E. junaluska)

Eastern half of North America

Small: up to 4.7 inches (12 centimeters)

Eastern or red-spotted newt (Notophthalmus viridescens)

Eastern half of North America, southern Canada, Texas, Oklahoma, Florida; watery areas


California newt (Taricha torosa)

California, west coast of United States

Up to 8 inches (20 centimeters)

Rough-skinned Oregon newt (Taricha granulosa)

Coastal Pacific northwest from southeast Alaska to San Francisco, California; aquatic or woodlands

5 to 8.5 inches (13 to 22 centimeters)

Fire-bellied newt (Cynops pyrrhogastea)

China and Japan; however, they are commonly bred and kept as pets

Varies; generally from 3 to 5 inches (8 to 13 centimeters)

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