Wildlife
Amphibians include frogs, salamanders and caecilians. A typical amphibian has a larval stage spent in water during which it breathes through gills, and an adult stage that is less tied to water when they rely on lungs. However, there are some species that skip the tadpole stage and others that keep their gills throughout their life.
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Amphibian characteristics
The first backboned animals to emerge on to land.
The first backboned animals to emerge on to land.
Stalking salamander
An amphibian's extraordinary tongue makes up for its lack of pace.
An amphibian's extraordinary tongue makes up for its lack of pace.
A comparison of amphibian size in relation to humans - from the 4m long prehistoric Koolasuchus to the 7cm long great crested newt.
Amphibians are members of the class Amphibia, a group of vertebrates whose living forms include frogs, toads, salamanders, newts and caecilians. They are characterized as non-amniote, ectothermic tetrapods, meaning their eggs are not surrounded by membranes, they are cold-blooded, and they have four limbs. Most amphibians lay their eggs in water and the larvae undergo metamorphosis from a juvenile form with gills to an adult air-breathing form with lungs. Some, however, are paedomorphs that retain the juvenile water-breathing form throughout life. Mudpuppies and olms are examples of this, retaining juvenile gills into adulthood. Adult amphibians also use their skin for respiration.
The three modern orders of amphibians are placed in the subclass Lissamphibia and are the Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians, limbless amphibians that resemble snakes). The total number of known amphibian species is approximately 7,000. They are superficially similar to reptiles, but reptiles, along with mammals and birds, are amniotes, having impervious membranes that surround the egg. Amphibians are ecological indicators, and in recent decades there has been a dramatic decline in amphibian populations around the globe. Many species are now threatened or extinct. The study of amphibians is called batrachology.
The earliest amphibians evolved in the Devonian Period from Sarcopterygians, fish that had lungs and bony fins, features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods, but were later displaced by reptiles and other vertebrates. Over time, amphibians shrunk and decreased in diversity, leaving the modern orders of Lissamphibia.
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Frogs and toads
Salamanders
Caecilians
Koolasuchus