The fossilised track of a giant water scorpion that lived 330 million years ago has been found in Scotland.
The six-legged water scorpion, Hibbertopterus , was about 1.6 metres long and one metre wide, and left a large track.
Dr Martin White, researcher at the University of Sheffield, discovered the large fossilised trackway in sandstone rock. When the giant water scorpion was alive, this would have been the shore of a lake or a swamp.
This is the first time Hibbertopterus has ever been recorded on land and the fossil trackways are some of the largest ever found. Larger trackways from the same animal are known in South Africa.
Survival out of water
The trackways indicate the creature could survive out of water. This was probably only for short periods though, perhaps to move from one pool of water to another. 'The animal would have dragged itself across wet mud, but it is debatable whether this was in or out of water,' said Dr Paul Selden, sea scorpion expert at the Natural History Museum.
Dr Paul Selden explains how the fossil was created after the animal moved across the mud. 'Sand would have washed over the mud and into the imprints, forming a natural cast of the trackway in the mud,' he said.
Hibbertopterus belongs to the group of extinct animals called Eurypterida, sometimes called sea scorpions. These giant creatures seem to have fed by sweeping up particles in muddy water and evidence suggests they were amphibious.
Despite being the size of man, Hibbertopterus was not an aggressive animal.
The Natural History Museum has a giant Carboniferous eurypterid in its collection, but not on public display, called Woodwardopterus. This is the closest relative to the infamous 'giant spider' Megarachne from Argentina - Dr Selden re-classified Megarachne as a giant eurypterid, not a giant spider, earlier this year.
From sea to land
The date of the fossil corresponds to the Carboniferous period of around 360 to 300 million years ago, a time when it is thought the earliest tetrapods, ancient four-legged creatures, were making their transition from the sea to land.
Dr Martin Whyte's research is reported in the journal Nature .