Photo: Oldest Shark Braincase Shakes Up Vertebrate Evolution



The earliest known braincase of a shark-like fish (above, a fossil of the creature) has thrown traditional assumptions about the early evolution of vertebrates into doubt, experts said in January 2009.

Data from the new fossil support an emerging idea that the Acanthodians, an ancient group of fish-like animals, included a diverse tableau of shapes and characterstics that defy clear-cut categories.

Image courtesy Martin Brazeau


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