150 million years ago, a horseshoe crab found itself at the bottom of a lagoon without any oxygen in the water. It walked for at least 9.7 meters berfore collapsing and dying.
It is sad for the horseshoe crab, but of benefit to modern paleontologists because the crab and its final steps have been preserved in an excellent fossil record. Dean Lomax of the Doncaster Museum and Art Gallery describes the find:
"The lagoon that the animal found itself in was anoxic, so at the bottom of these lagoons there was no oxygen and nothing was living," Mr Lomax told the BBC.
"This horseshoe crab [Mesolimulus walchi] found itself on the lagoon floor and we can tell by looking at the trace that the animal righted itself, managed to get on to its feet and began to walk," he explained.
However, the anoxic conditions of the lagoon floor quickly proved fatal to the arthropod and it soon began to struggle.
"We started to study the specimen closer and saw that the walking patterns and the animal's behaviour started to change. The leg impressions became deeper and more erratic, the telson (the long spiny tail) started being lifted up and down, up and down, showing that the animal was really being affected by the conditions," he said.
"To find a trackway and its track-maker preserved together in the fossil record is extremely rare. Working out who made a trackway is normally like detective work. In this case, the suspect has been caught in the act," Dr Nic Minter, currently of the University of Saskatchewan, Canada, who was not involved in the study, told BBC News.