Geologic period: Modern
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Crossopterygians are a class of lobe-finned fishes known from fossils dating as far back as the Silurian. Their living descendants today include the coelacanth, modern lungfish and all tetrapods -- amphibians, reptiles, birds, and mammals.
Did you know?
Lungfish found today still retain some very primitive characteristics of ancient crossopterygians, including the ability to breath air (rather than to absorb oxygen through gills while underwater) and their characteristically lobe-shaped fins.