520millionyeA fossil recently discovered in southern China is so well-preserved that scientists can examine each of the animal’s individual nerves, visibly. Of course, this is the very first time researchers have found anything this old yet this detailed.

The fossil is that of a Chengjiangocaris kunmingensis, and it lived—not surprisingly—during the Cambrian ‘explosion.’ This is the famous epoch during which rapid organisms on this planet underwent rapid evolutionary development, approximately, half a billion years ago. This particular organism belongs to a group called fuxianhuiids, which was an early ancestor of the modern arthropod—the incredibly diverse group we know today contains insects, spiders and crustaceans.

And C. kunmingensis does resemble a crustacean. It has a broad, somewhat heart-shaped head shield with a long torso and pairs of legs of different sizes. While carefully preparing the fossil—involving the tedious removal of the specimen from the surrounding rock—the researchers began to see great detail of the animal’s soft tissue as well.

“This is a unique glimpse into what the ancestral nervous system looked like,” said explains Javier Ortega-Hernández, of the University of Cambridge Department of Zoology. “It’s the most complete example of a central nervous system from the Cambrian period.”

In just the last five years, researchers identified partially-fossilized nervous systems from several species during the Cambrian period. These have mostly been, however, brains, limiting nerve study. While this may have been helpful in terms of studying the brain, this has not helped to reveal more about the rest of the nervous system’s.

  1. kunmingensis is similar to modern arthropods because it had a nerve cord, similar to the spinal cord of vertebrates. This nerve cord ran through the body, with bead-like ganglia that could control a single pair of legs for walking. Upon closer examination, though, scientists found that this specimen’s ganglia were exceptionally preserved to reveal, in great detail, dozens of spinal fibers measuring approximately five-thousands of a millimeter in length.

Ortega-Hernandez goes on to say, “These delicate fibers displayed a highly regular distribution pattern, and so we wanted to figure out if they were made of the same material as the ganglia that form the nerve cord. Using fluorescence microscopy, we confirmed that the fibers were in fact individual nerves, fossilized as carbon films, offering an unprecedented level of detail. These fossils greatly improve our understanding of how the nervous system evolved.”