Reptiles arose over 300,000,000 years ago, having evolved from a salamander-like ancestor. They represent a completion of the transition from life in water to a fully terrestrial lifestyle (although some reptiles have returned to the water). Waterproof skin and a water-resistant egg means that reptiles can live in places and ways that amphibians can't.
They range in size from tiny geckos that easily rest on a penny to the giant Komodo dragon. Venom is widespread among reptiles, from many lizards and snakes that will, at most, produce an irritating sensation with their salivary secretions to deadly coral snakes and their relatives which produce neurotoxins that can cause cardiac arrest. However, the vast majority of reptiles are absolutely harmless to humans.
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