A scientist poring over 330-million-year-old tracks in a layer of sandstone in Scotland believes they were made by an extraordinary water scorpion that was as big as a man. The huge six-legged creature was about 1.6 metres (64 inches) long and a metre (40 inches) wide, according to the study, published on Thursday in Nature, the weekly British science journal.
The trackway, measuring six metres (20 feet) long, was found on the overhang of a bed of sandstone that, 330 million years ago, was probably close to the sea and had the consistency of soft plaster.
The traces comprise crescent-shaped prints left by the creature's limbs and a sinuous curve believed to have been gouged out by its tail.
"The slow stilted progression, together with the dragging of the posterior, indicates that the animal was not buoyant and that it was probably moving out of the water," says Martin Whyte, a geography professor at Britain's University of Sheffield.
The find is unique, not just because of the gigantic size of the arthropod, but for the evidence it offers that this invertebrate species could survive out of water.
Until now, the only advanced creatures believed to have ventured onto land from the sea at that era were early tetrapods -- vertebrates with four limbs.
