Complete 520-million-year-old nervous system discovered

18 October 2013

The oldest intact nervous system has been identified in a 520-million-year-old clawed animal related to spiders and scorpions.

An international team of researchers, including Museum palaeontologists Dr Greg Edgecombe and Dr Xiaoya Ma, described the fossil as having a brain, nervous tissues associated with the eyes, and a major part of the nerve cord, in their paper published yesterday in Nature.

The team CT-scanned the fossil and compared it to modern relatives to better understand its position in the evolutionary tree.

Place in evolution

The creature is part of a very large group of organisms called arthropods, which include insects, spiders, lobsters and millipedes. Arthropods can have many body parts, for example antennae, jaws and legs.

Researchers usually compare the physical characteristics of these body parts in fossils to decide how arthropods are related. Imaging of the nervous system allows scientists to see which body parts are connected to which parts of the brain and make more reliable comparisons between species.

‘For the first time we can analyse how the segments of these fossil arthropods line up with each other the same way as we do with living species - using their nervous systems,' said Edgecombe.

The fossil creature’s nervous system is very similar to that of today’s horseshoe crabs and scorpions. It has two large appendages attached to its head which the team believes, based on the nervous system linkages, later evolved into spiders' biting mouthparts.

New technique

‘It is very exciting to use new techniques to successfully reveal such a complete central nervous system from a 520-million-year-old fossil, and in such detail,’ said Ma. ‘This research helps to open up further possibilities in the relatively new field that we call neuropalaeontology.’

While the Chinese fossil arthropod is especially well preserved, Edgecombe said similar results could be gained from many other specimens.

‘This specimen may not be as special as it first seems.  It is likely that applying the same imaging techniques to other specimens will lead to interesting discoveries.’

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