Nervous System Found In Fossil Is Well-Preserved, Really Old

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A rare 515-million-year-old arthropod fossil has recently been discovered in China. The fossil is from the early Cambrian period and goes back well over 500 million years; what’s especially rare about the find is the existence of an exquisitely preserved nervous system that truly surprised researchers.

The complex structure should provide researchers answers into nervous system evolution

The fossil in question is the remains of a Chengjiangocaris kunmingensis, a crustaceanlike creature that resembled a shrimp about to go jousting as it featured something quite similar to a helmet. The creature itself lived 520 million years ago in what is now South China and researchers hope it will provide insight into the evolution of the nervous systems that living creatures today have. The scientists were quite pleased with the find as individual nerve structures were identifiable clustered around a “ropelike” central nerve cord.

Researchers reported their findings in a paper published Monday in the journal Proceedings of the National Academy of Sciences.

“Because nervous systems are extremely rare in the fossil record, finding one is extremely informative about the early evolution of these animals,” study co-author Javier Ortega-Hernández, a biologist in the Department of Zoology at the University of Cambridge, in the United Kingdom told The Christian Science Monitor in a phone interview earlier this week.

The arthropod would have had a fairly mundane live. Essentially it has an exoskeleton, jointed limbs, a segmented body and up to as many as 80 plus legs and would have simply begun its life on the sea floor where it would spend its remaining days just scuttling about like a marine centipede.

The exoskeleton had nerve tissue masses called ganglia associated with each pair of legs. Both the ganglia and the legs were at their biggest near the head and then both would have gotten smaller as they moved further from the head and closer to the “tail.”

“Some of the largest individuals can reach up to 15 centimeters (6 inches) long, and they had at least 80 legs,” said Ortega-Hernández via email with Live Science.

What preserved the fossil?

It’s nothing new that scientists are treated to fossilized bones, shells, teeth and other tough bits but it’s exceptionally rare that something with the softer tissues like a nervous system is preserved. You need certain conditions and a fair bit of a luck to make a find like this. Thankfully, according to Ortega-Hernández, the Xiashiba area in Kunming (Yunnan Province) is “world famous” for preserving these softer tissues. According to the doctor, the animal was likely buried in fine sediment in a low-oxygen environment capable of slowing or even stopping decay while keeping it “safe” from scavengers and microbes.

“Eventually the carcasses become preserved in the fossil record, and the limited decay allows for the preservation of amazing morphological detail,” he said.

Not only was the soft tissue preserved but it was a preserved on a minute scale. The team found nerve fibers, under a microscope  that were around five-thousandths of a millimeter in length—”less than [the width of] a human hair,” according to  Ortega-Hernández.

“Our jaws dropped when we put the specimens under the microscope and observed the fine nerves on the sides,” he told Live Science. “It was hard to believe that something so small would be preserved along with the main nerve cord, but even more so because they show a unique organization that is otherwise unknown in living arthropods.”

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