March 3, 2009

Fossilized Fish Brain Found Fish From The Midwest

Researchers studying a type of fish that once lived in what is now Kansas and Oklahoma have discovered a 300-million-year-old fossilized brain.

"For a long time, paleontologists have used the shape of the cranial cavity to research the general morphology of the brain, because soft tissue was not available until today," said Alan Pradel of the National Museum of Natural History in Paris.

"Soft tissue has fossilized in the past, but it is usually muscle and organs like kidneys because of phosphate bacteria from the gut that permeates into tissue and preserves its features," says John Maisey, Curator in the Division of Paleontology at the American Museum of Natural History and a co-author of the report. "Fossilized brains are unusual, and this is by far the oldest known example."

According to reports in the online edition of Proceedings of the National Academy of Science by Maisey and co-authors, the brain was discovered in a fossilized iniopterygian in Kansas.  They then sent it for scanning at the European Synchrotron Radiation Facility in Grenoble, France.  Iniopterygians are extinct relatives of ratfishes, also known as ghost sharks. 

CAT scans and X-ray synchrotron microtomography revealed a fossilized blob inside the braincase, and after closer study it found that it was the fossilized brain of the ancient creature. 

"Now that we know that brains might be preserved in such ancient fossils, we can start looking for others. We are limited in information about early vertebrate brains, and the evolution of the brain lies at the core of vertebrate history," Maisey said.


Image Caption: The structure of the skull (foreground) of a 300-million-year-old iniopterygian fish from Kansas remotely related to living ratfish is elucidated thanks to holotomography, a technique based on synchrotron X-ray phase contrast imaging (background), and yields the first hint at an exceptional mineralization of the brain (orange). Credit: PNAS/Philippe Janvier (CNRS, Museum National d'Histoire Naturelle)


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