X-rays unravel fossil secrets

By using an X-ray imaging technique, palaeontologists have discovered borings made by shell invertebrates in a sea urchin fossil.

An international research team led by the University of Bristol used an X-ray computed tomography and found that a 10-million-year-old sea urchin fossil was riddled with borings made by a type of shelled  molluscs known as bivalves.

“This demonstrates the importance of ancient organisms not only as key members of fossil ecosystems, but also how the shells of these organisms contribute to and influence the nature of the sediments which ultimately make up the rock record,” said research associate Professor Dr James Nebelsick from the University of Tübingen in Germany.

In the study, published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, the team studied a sea urchin specimen from Miocene of Fuente del Jarro in Spain and discovered that fossilised boring bivalves were preserved inside the specimen in very large numbers. These findings prove that bivalves were using sea urchins as an ‘island’ habitat on the seafloor, similar to modern bivalves.

Research leader Dr Imran Rahman, a palaeontologist in Bristol’s School of Earth Sciences said: “We had no idea there would be so many bivalves inside the sea urchin. This goes to show the importance of CT scanning for understanding long-dead organisms and their ecosystems.”

The images also allowed the scientists to classify the bivalves to the genus Rocellaria, members of which are known to bore into rocks and shells today.

“In some cases articulated bivalve shells are still present within the chambers, allowing for the identification of the tracemaker as the boring bivalve Rocellaria, reaffirming these tube-dwelling animals as borers, burrowers and crypt-builders,” the researchers said in their paper.

Paper: http://www.sciencedirect.com/science/article/pii/S0031018215003880