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Few of today's species are the only remaining examples of long-extinct marine families. Today's hagfish and lampreys bear a resemblance to the now-extinct ostracoderms, which were jawless fish. But the most well-known throwback to Mesozoic marine life may be the coelacanth, the last known marine sarcopterygian. Sarcopterygians were lobe-finned, bony fish. There are plenty of other sarcopterygians in the world, though -- the four-legged, vertebrate tetrapods arose from ancestors that diverged from the sarcopterygians long before the Mesozoic Era.
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