About: Shark evolution   Sponge Permalink

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Contrary to popular belief, sharks have not remained unchanged for 300 million years. However, many of the families we have today have been in existence for perhaps the last 150 million years. Mostly only the fossilized teeth of sharks are found, although often in large numbers. In some cases pieces of the internal skeleton or even complete fossilized sharks have been discovered. Estimates suggest that over a span of a few years a shark may grow tens of thousands of teeth, which explains the abundance of fossils. As the teeth consist of calcium phosphate, an apatite, they are easily fossilized.

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  • Shark evolution
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  • Contrary to popular belief, sharks have not remained unchanged for 300 million years. However, many of the families we have today have been in existence for perhaps the last 150 million years. Mostly only the fossilized teeth of sharks are found, although often in large numbers. In some cases pieces of the internal skeleton or even complete fossilized sharks have been discovered. Estimates suggest that over a span of a few years a shark may grow tens of thousands of teeth, which explains the abundance of fossils. As the teeth consist of calcium phosphate, an apatite, they are easily fossilized.
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dbkwik:fossil/prop...iPageUsesTemplate
abstract
  • Contrary to popular belief, sharks have not remained unchanged for 300 million years. However, many of the families we have today have been in existence for perhaps the last 150 million years. Mostly only the fossilized teeth of sharks are found, although often in large numbers. In some cases pieces of the internal skeleton or even complete fossilized sharks have been discovered. Estimates suggest that over a span of a few years a shark may grow tens of thousands of teeth, which explains the abundance of fossils. As the teeth consist of calcium phosphate, an apatite, they are easily fossilized. Instead of bones, sharks have cartilaginous skeletons, with a bone-like layer broken up into thousands of isolated apatite prisms. When a shark dies, the decomposing skeleton breaks up and the apatite prisms scatter. Complete shark skeletons are only preserved when rapid burial in bottom sediments occurs.
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