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Recently unearthed fossilized brains belonging to ancient arthropods have blown paleontologists’ minds. The exceptionally well-preserved prehistoric vestiges were discovered by a team of researchers, led by Nicholas Strausfeld, Regents’ professor at the Department of Neuroscience, from the University of Arizona.
An initial report regarding a similar historic find was published in the journal Nature, in 2012, but at the time there was heavy criticism from other experts, who had claimed it had all been just an exceptional occurrence or an artificial artifact.
Brain tissues are normally too fragile, watery and soft, so they begin decaying shortly after death. Therefore, no such fossils dating back from millions of years ago would’ve seemed likely to be encountered.
However, now the original study authors have written two other scientific papers, whose ground-breaking findings were revealed in the journals Current Biology and Philosophical Transactions of the Royal Society B: Biological Sciences.
Experts examined 7 other new fossils, identified in lower Cambrian deposits at Maotianshan Shales, in Chengjiang County, Southwest China. Through electron microscopy, they proved that these remnants contained neural tissue, as flat carbon layers, which in some cases were covered by a thin sheet of pyrite.
Neural structure was the same across all the specimens, and included 3 pieces of brain tissue, as well as optic tracts and optic lobes, which extended from the eye protrusions to the front of the brain.
The brains belong to an ancient arthropod, called Fuxianhuia protensa, which inhabited the ocean floor approximately 520 million years ago. The species was actually similar to modern-day shrimps, and its brain also greatly resembled that of decapod crustaceans.
Paleontologists have even come up with a possible explanation regarding how brains were fossilized. For such a process to take place, the animal has to be quickly buried, so that scavengers can’t reach it. Provided that water is depleted of oxygen (anoxic), tissues are no longer disintegrated by bacteria, and can be successfully preserved.
Therefore, it appears that the prehistoric arthropods might have died after being trapped under quick and heavy mudslides. Scientists reconstructed that event in an experiment using cockroaches and sandworms.
They proffer that the nervous system of the crustaceans managed to survive despite pressures from the environment, because it was extremely compact. This hypothesis is supported by the fact that even modern arthropods have the densest brain tissues in the world.
In the trial it was proven that the creatures’ neural networks can indeed maintain their structure even when buried under wet clay, at room temperatures.
In the next stage, the brains underwent a process of dewatering due to compression caused by the sediments building up above it. This is how tissues were gradually emptied of hydrogen and oxygen, and they became flattened films of carbon, withstanding the test of time.
Now that they’ve shown that neural tissues can indeed become fossilized, researchers are currently conducting follow-up studies, in order to further investigate the mystery of brain evolution across the ages.
Their prior academic paper had pointed out that ancient arthropods actually had intricate nervous systems, composed out of 3 segments served by a network of blood vessels.
This indicates that the brains of these extinct species might have been similar to those of modern-day insects, so other less complex arthropods such as crustaceans encountered nowadays might have regressed from common ancestors.
Image Source: Cell.com
