Scientists in China have discovered a 419 million-year-old fish that has a distinct face, the earliest known animal with pronounced features, which could be a missing link in the development of vertebrates.
The fish fossil find in China's Xiaoxiang Reservoir, reported by the journal "Nature" on Thursday, is the most primitive vertebrate discovered with a modern jaw, including a dentary bone found in humans.
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It "finally solves an age-old problem about the origin of modern fishes," said John Long, a professor in palaeontology at Flinders University in Adelaide.
Scientists were surprised to find that the heavily armored fish, Entelognathus primordialis, a previously unknown member of the now extinct placoderm family, had a complex small skull and jaw bones. It is not clear in "Nature" when exactly the fossil was found.
The fish fossil appears to disprove earlier theories that modern vertebrates with bony skeletons, called osteichthyes, had evolved from a shark-like creature with a frame made of cartilage.
Instead, the Chinese fossil provides a missing branch on the evolutionary tree, predating that shark-like creature and showing that a bony skeleton was the prototype for both bony and cartilaginous vertebrates.
"We now know that ancient armored placoderms gave rise to the modern fish fauna as we know it," said Long, who was not part of the team in China.
Long described the fish fossil discovery as "the most exciting news in palaeontology since Archaeopteryx or Lucy," referring to two fossil discoveries that are crucial to our understanding of the evolution of birds and humans.
"This is a very, very deep part of our own family tree, suggesting that those features we still have are of much greater antiquity than we might have previously thought,"
said Rhitu Chatterjee, of NPR, of the discovery.
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