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Amphibians

Amphibians

Amphibian are tetrapods, which means they have four limbs and within the class Lissamphibia, there are three basic groups – newts and salamanders, frogs and toads and caecilians. There are roughly 5000-6000 amphibians alive today, but many are under threat.

When They First Appeared

The ancestors of the amphibians living today crawled out of the water and adapted to living on the land during the Devonian Period, approx. 370 millions years ago. As they evolved they developed a skeleton that became rigid enough to support them on land, they also developed leg bones and nostrils which were required for life out of the water.

The world in the Devonian Period was very different from today – there were no reptiles, birds or mammals. Invertebrates inhabited the earth along with prehistoric plants such as ferns, mosses and liverworts.

The Three Groups of Amphibians

Frogs and Toads – This most diverse group of amphibians has about 4380 species of toads and frogs. The adults have large heads with large eyes, 4 legs with the hind legs longer and more powerful than the front ones, they have no tail.

Newts and Salamanders – This group has two very different habits – newts live almost totally on land while salamanders live exclusively in the water. The group has about 470 known species. Their bodies are slender with 4 legs and a long tail.

Caecilians – They resemble snakes or worms but not even closely related to them. Through evolution these amphibians lost their limbs but do have a short tail. Although Caecilians are the least known, about 170 species exist within this group.

Without scales or hair, amphibians’ skin is very permeable to water and gases. This makes them particularly vulnerable to the toxins such as pesticides, herbicides and other pollutants that are pumped into the air and water. As a consequence they are declining and showing us an environment in trouble.

Amphibians Africa. Lots of interesting information regarding amphibians in Africa, explaining the three groups of amphibians.

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