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Figure 1. White sharkClick to Enlarge Image

The evolution of jaws was a crucial step in vertebrate history, but it took place so long ago that fossils from this period consist mostly of teeth and a bewildering variety of skin scales. Now an almost complete shark fossil gives paleontologists the opportunity to investigate the poorly understood transition between sharks and modern fishes and to interpret isolated fossils from a new perspective. The remarkably intact 409 million year-old example preserves the braincase, jaws, teeth and pectoral fins in the correct anatomical position. Based on this finding, the authors revise the geography of early shark evolution and question the accepted picture of shark evolution as it relates to other major fish groups.

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