Saturday, March 16, 2013

Ancient eyes

The last time I blogged about fossils, it was because one had died in such a way that its special features could be seen. This time it's because those features have been revealed by modern equipment. Brigitte Schoenemann, a physiologist at Germany's University of Bonn and University of Cologne, has used a computed tomography (CT) scanner and a particle accelerator's high energy x-rays to examine the eyes of the bug-like trilobite, which scoured the ocean floor hundreds of millions of years ago (rendering above). She has imaged the extinct animal's entire visual system, down to the level of fossilized individual cells. Trilobites had compound eyes with multiple lenses, beneath which round sensory cells were arranged like petals around a diamond-shaped photoreceptor able to pick up the dim light that filtered down through the water. Pigment cells filled in the space between the blooms. Scientists were surprised that the delicate visual cells survived and at how closely they resemble the eyes of today's horseshoe crabs. "If you have an optical system that works, it can last," says Richard Fortey, a paleontologist at the Natural History Museum in London.

 

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