More than half a billion years ago, scurrying along the ocean floor, an ancient relative of modern day creepy crawlies gave its final twitch as it died.
Now, 520 million years later, a team of archaeologists which uncovered its remains believe it to be one of the oldest and most detailed fossilised nervous systems from the period ever found.
Its fossilised remains have been so well preserved that individual nerves can be seen, providing scientists with new insight into how the systems of insects, crabs and spiders, have evolved.
Scientists who have uncovered an ancient fossilised relative of modern day arthropods say it is the most complete example of a central nervous system from the Cambrian period, 520 million years ago
The crustacean-like creature, called Chengjiangocaris kunmingensis, belonged to a group of animals called the fuxianhuiids, which were early ancestors of modern arthropods.
It lived during the Cambrian explosion, a period of rapid evolutionary development when the first major animal groups are believed to have emerged.
'This is a unique glimpse into what the ancestral nervous system looked like,' said Dr Javier Ortega-Hernández, of the University of Cambridge's Department of Zoology and co-author of the study.
'It's the most complete example of a central nervous system from the Cambrian period.'
'The more of these fossils we find, the more we will be able to understand how the nervous system, and how early animals, evolved.'
. The crustacean-like creature, called Chengjiangocaris kunmingensis, belonged to a group of animals called the fuxianhuiids, which were early ancestors of modern arthropods - a family which includes insects such as the praying mantis (left), spiders such as the tarantula (middle) and crustaceans such as red crabs (right)
The central nervous system in arthropods consists of a condensed brain and a chain-like series of interconnected masses of nervous tissue that resemble a string of beads.
Preparation of the fossils involves chipping away at the surrounding rock with a fine needle, with researchers then able to view the hard body parts and fossilised soft tissue.
The nervous system and soft tissues are essentially made of fatty-like substances so finding them preserved as fossils is extremely rare.
The exceptionally well-preserved nerve cord of C.kunmingensis represents a unique structure that is otherwise unknown in living organisms, with the researchers saying it shows just how important the fossil record is in understanding the evolution of animals in the period.
A closer look at the animal's fossil revealed tiny fibres just five thousandths of a millimetre long, branching out at regular intervals.
'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 Dr Ortega-Hernández.
Analysis using fluorescence microscopy showed that they were in fact nerves, offering 'an unprecedented level of detail'
The image shows a complete fossilised specimen of C.kunmingensis (left) and a reconstruction of its body (right). A closer look at the animal's fossil revealed tiny fibres just five thousandths of a millimetre long, branching out at regular intervals, which analysis showed to be nerves
The nervous system and soft tissues are essentially made of fatty-like substances so finding them preserved as fossils is extremely rare
Dr Ortega-Hernández added: 'These fossils greatly improve our understanding of how the nervous system evolved.'
Over the past five years researchers have identified partially-fossilised nervous systems in several different species from the period - but these have mostly been fossilised brains.
In most of those specimens the fossils only preserved details of the profile of the brain - meaning the amount of information available has been limited.
Researchers first identified a fossilised central nervous system in 2013 but the new material has allowed them to investigate the significance of these findings in much greater depth.
The findings, published in the journal Proceedings of the National Academy of Sciences, are helping researchers understand how the nervous system of creepy crawlies with jointed legs evolved.
WHAT SPURRED THE CAMBRIAN EXPLOSION 542 MILLION YEARS AGO?
The rare find is of an animal that lived more than 520 million years ago during the Cambrian explosion
The 'Cambrian explosion' began roughly 542 million years ago after the end of the Ediacaran Period.
During this time, large numbers of complex animal species emerged.
Researchers argue many possible causes for the Cambrian explosion, from the rise of atmospheric oxygen to the rise in carnivorous species.
What has largely been accepted as the second oxygenation event during the Late Neoproterozoic Era from 750 to 540 million years ago is thought to have continued the process of oxygenating Earth's atmosphere.
Some scientists believe this gave rise to the 'Cambrian explosion,' of 540-520 million years ago that birthed diverse animal groups.
But, a new hypothesis suggests the evolutionary changes may have stemmed from the reversals of Earth's magnetic field.
A reversal period can occur over 7000-10,000 year, weakening the ozone layer between 20 and fourty percent in some areas, and allowing in more harmful solar radiation and cosmic rays.
With UV radiation pouring in, animals that could escape the light would have a much more favourable chance of survival.
Hard shells and complex eyes would allow organisms to seek shelter and burrow deeply, facilitating the 'flight from light.'
And, it would allow these animals to thrive in deeper areas with stronger waves.
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