Success on land also required tetrapods to find a way to reproduce. With virtually no fossil evidence of reproductive strategies, it is assumed by most paleontologists that the first tetrapods were most similar in this regard to today's amphibians. Amphibians such as frogs and salamanders must lay their eggs in water, where the young hatch as fully aquatic, gill-breathing tadpoles. Evidence of fossil tadpoles from the Carboniferous confirms that some early tetrapods reproduced in this manner. The young hatched in the water as tadpoles and breathed through gills until they underwent a metamorphosis and took on the four-legged form of adults.
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