Amphibians are a class of cold-blooded (in the traditional sense) animals that include the frogs, toads, newts, salamanders and caecilians. These familiar animals evolved during the Devonian period, around 370 million years ago, from lobe-limbed fish similar to today's coelacanths and lungfish. While superficially similar to some lizards, amphibians require a body of water in order to complete their breeding cycle. They also have semi-permeable skin, through which they can breathe and this feature, among others, make them susceptible to environmental pollution and, as such, they're often regarded as an indicator species. Today, the class comprises some 8,000 species worldwide, the majority (almost 90%) of which are frogs.


Amphibians and Reptiles: A Natural History of the British Herpetofauna - by Trevor Beebee & Richard Griffiths
HarperCollins Publishers -- 2000 -- ISBN: 978-0002200837

Biology of Amphibians - by William Duellman & Linda Trueb
The Johns Hopkins University Press -- 1994 -- ISBN: 978-0801847806

Frogs & Toads - by Trevor Beebee
Whittet Books -- 2007 -- ISBN: 978-1873580288

Herpetology: An Introductory Biology of Amphibians and Reptiles - by Laurie Vitt & George Zug
Academic Press Inc -- 1993 -- ISBN: 978-0127826202

Tadpole Hunter - by Arnold Cooke
Pelagic Publishing -- 2023 -- ISBN: 978-1784274481

The New Encyclopedia of Reptiles and Amphibians - by Tim Halliday & Kraig Alder (eds)
Oxford University Press -- 2004 -- ISBN: 978-0198525073