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From the Cambrian Explosion, a Remarkably Preserved Image of a Nervous System


Quite beautiful, isn't it? Like a dragon float from a Chinese New Year parade. The Washington Post calls it an "ugly arthropod." Are they blind?

News from Cambridge University of an unprecedented Cambrian find from, in fact, China:

A 520 million-year-old fossilised nervous system -- so well-preserved that individually fossilised nerves are visible -- is the most complete and best example yet found, and could help unravel how the nervous system evolved in early animals.

How did this arthropod's nervous system "evolve"? Suddenly, it seems, all but out of a clear blue sky, as far as we have any reason to say. What's striking about the new images of Chengjiangocaris kunmingensisis, a product of the Cambrian explosion, is the remarkable detail preserved from soft tissue. The difficulty of preserving soft tissue was once given as a reason that the Cambrian animals' precursors seem not appear in the fossil record.

At some earlier stage of life's history, these features were not there -- then they were. This is said to help "unravel" the mystery of evolution. More:

Researchers have found one of the oldest and most detailed fossils of the central nervous system yet identified, from a crustacean-like animal that lived more than 500 million years ago. The fossil, from southern China, has been so well preserved that individual nerves are visible, the first time this level of detail has been observed in a fossil of this age.

The findings, published in the Proceedings of the National Academy of Sciences, are helping researchers understand how the nervous system of arthropods -- creepy crawlies with jointed legs -- evolved. Finding any fossilised soft tissue is rare, but this particular find, by researchers in the UK, China and Germany, represents the most detailed example of a preserved nervous system yet discovered.

Again, the question of what this means for evolution:

For [Javier Ortega-Hernández, of the University of Cambridge's Department of Zoology,] and his colleagues, a key question is what this discovery tells us about the evolution of early animals, since the nervous system contains so much information. Further analysis revealed that some aspects of the nervous system in C. kunmingensis appear to be structured similar to that of modern priapulids (penis worms) and onychophorans (velvet worms), with regularly-spaced nerves coming out from the ventral nerve cord.

In contrast, these dozens of nerves have been lost independently in the tardigrades (water bears) and modern arthropods, suggesting that simplification played an important role in the evolution of the nervous system.

The nervous system is information rich, and "these dozens of nerves" were lost by tardigrades and today's arthropods. These latter creatures evolved in part by losing information, not gaining it -- becoming simpler, not more complex. So where did the information come from in the first place? They don't say. They can't say.

Image: C. kunmingensis, by Jie Yang via Cambridge University.