310-Million-Year-Old Fossil Brain Discovered ‘Perfectly Preserved’ In Illinois
Photo 48287067 © Lukas Blazek | Dreamstime.com
In a 310-million-year-old horseshoe crab lives a fossilized brain, one never seen before. Discovered at Mazon Creek, Illinois, the researchers who uncovered this rare specimen deduced that the conditions must’ve been “just right”: the delicate soft tissue of the animal was “perfectly” preserved.
Horseshoe crab fossils are not uncommon, but the prospect of being able to study their brains and the evolution of the species is rare, given that this is the “first and only” evidence for a brain in a fossil of the creature, explains Russell Bicknell, lead author of the research team and paleontologist at the University of New England.
“Soft tissues that make up brains are very prone to rapid decay,” Bicknell tells Live Science. “In order for them to be preserved, either very special geological conditions, or amber, are needed.”
Mazon Creek’s deposits are composed of siderite, an iron carbonate mineral. It forms concretions that can quickly encase and fossilize a dead form. Though the body was fossilized, the softness of the brain tissue meant the brain still decomposed and eventually disappeared, as many do.
But this time, during the process, it was replaced by a clay mineral called kaolinite. This essentially created a perfect cast of the brain, which researchers could then use to study how the species’ central nervous system may have evolved over millennia.
Despite all this, what the researchers found was that the ancient brain they dated back to the Carboniferous period (approximately 359 million to 299 million years ago) was “pretty much the same” as the brains of the modern horseshoe crab, Bicknell reveals. The full study was published in Geology on Monday, July 26.
Now equipped with the knowledge that Mazon Creek’s conditions are ideal for this kind of preservation, the search for even more uniquely retained, perfect-condition ancient brains is now on. Who knows what surprising specimens might come up next?
[via Live Science, cover image ID 48287067 © Lukas Blazek | Dreamstime.com]
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