Researchers from the University of Cambridge have discovered one of the oldest and most detailed central nervous system fossils ever seen. The fossil, which was found in southern China, is believed to have originated from a crustacean-like animal that inhabited the Earth more than 500 million years ago and is so well preserved that individual nerves are visible. The findings will help scientists better understand the evolution of the nervous system of arthropods.
The animal - Chengjiangocaris kunmingensis - existed during the Cambrian "explosion," when most of the animal groups first appeared in the fossil records. It belongs to a group of animals called fuxianhuiids and is believed to an early ancestor of modern arthropods, which include many different species of insects, spiders and crustaceans.
"This is a unique glimpse into what the ancestral nervous system looked like," Javier Ortega-Hernández, co-author of the study, said in a press release. "It's the most complete example of a central nervous system from the Cambrian period."
In the past, partially fossilized nervous systems have been discovered, all from numerous different species from the Cambrian period, but most of these specimens only preserved details on the brain's profile, not individual nerves.
Much like humans, C. kunmingensis possessed a nerve cord that ran throughout its body and each of their ganglia controlled a single pair of walking legs. Upon close examination, the team observed dozens of spindly fibres in the preserved ganglia.
"These delicate fibres 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," said Ortega-Hernández. "Using fluorescence microscopy, we confirmed that the fibres were in fact individual nerves, fossilised as carbon films, offering an unprecedented level of detail. These fossils greatly improve our understanding of how the nervous system evolved."
The findings were published in the Feb. 29 issue of the Proceedings of the National Academy of Sciences.
