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Frogs mating in the waterFrogs mating in the water Amphibians are a small group of cold-blooded, vertebrate animals. They include two main groups: the salamanders and newts, and the frogs and toads. The word “amphibian” means “double life”. Most amphibians spend the first part of their lives underwater, breathing through gills. Their adult lives are generally spent on land, breathing through lungs. They usually return to the water to lay eggs. All amphibians, in their adult forms, are predators.

Eryops, a giant prehistoric amphibianEryops, a giant prehistoric amphibian

The first amphibians

Amphibians were the first vertebrates to live on land more than 360 million years ago. They evolved from fish that had moved on to the land and developed lungs. Early amphibians looked similar to salamanders. Some were huge, reaching 4 metres (13 feet) in length. They fed on fish, insects and other invertebrates. All early amphibians had to return to water to lay their eggs.

The smallest amphibian (and the smallest animal with a backbone) is Paedophryne amanuensis from Papua New Guinea. It is only 7 mm (0.3 inch) long.

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