It鈥檚 the most ancient nervous system we鈥檝e ever seen, preserved inside 520 million-year-old fossils. What鈥檚 more, the nervous systems of these creatures鈥� modern-day descendants are less intricate, proving that evolution isn鈥檛 a one-way street to complexity.
Found in South China, the five Cambrian fossils belonged to a group of organisms that gave rise to the arthropods, including insects, spiders and crustaceans. The fossils are of Chengjiangocaris kunmingensis, a creature around 10 centimetres long, with a segmented body, multiple pairs of legs and a heart-shaped head.
But most interesting of all is its nerve cord and associated neurons. Together, the fossils show the entire nervous system of the organism, apart from its brain 鈥� making this the oldest preserved nervous system that has ever been found.
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鈥淭he detail of this fossil is exquisite,鈥� says of the American Museum of Natural History in New York, who was not involved in the work. 鈥淭he information from this specimen unravels transitions in how the nervous systems of arthropods evolved.鈥�
The animal had a nerve cord that ran the length of its body, with bulbous nodes of neurons called ganglia located between each pair of legs. 鈥淚t鈥檚 almost like a mini-brain for each pair of legs,鈥� says of the University of Cambridge, whose team analysed and described the fossil.
Surprisingly, the team found dozens of fine, subsidiary nerves fanning out across the entire length of the nerve cord, making this nervous system more complex than those seen in today鈥檚 descendants.
鈥淚t may be that the more streamlined arrangements in modern arthropods 鈥� renowned for their fine movements 鈥� allow finer motor control,鈥� says Ortega-Hern谩ndez.
PNAS
