Sunday 31 May 2015

Missing link in shark evolution found

'Missing link' in shark evolution found in 380m-year-old Australian fossil
Fossilised skeleton found in Kimberley shows sharks once had bone cells within cartilage, suggesting a sophisticated evolutionary path.A 380m-year-old fossil found in Western Australia has been hailed as the “missing link” in shark evolution, revealing the marine predator has a far more sophisticated lineage than previously thought.The fossilised skeleton, jaws and teeth, found at the Gogo formation in the Kimberley region of WA, shows the ancient shark had a small amount of bone as well as cartilage.As modern-day sharks have fully cartilage skeletons, the fossil suggests they evolved from an earlier, bonier fish, transforming to a cartilage skeleton to make them lighter, more nimble and quicker through the water.It was previously thought that sharks came from a primitive lineage that didn’t ever develop bone, unlike other fish.
“That idea of shark evolution has been completely turned on its head,” said palaeontologist John Long of Flinders University, who discovered the fossil. “Cartilage is seen as the precursor to bone, so sharks must be primitive because they never developed bone. This fossil suggests sharks went in the opposite direction because modern sharks lost bone.”

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