Fossils of Ancient Horseshoe Crab Shed Light on its Final Moments

Researchers have reconstructed the fossil record of a death march by an ancient horseshoe crab, reported the BBC.

Back in 2002, researchers discovered a fossil trackway which was 31.8 feet long (9.7m) and showed the movements of the horseshoe known as "mortichnia" or "death march" or "last walk" of a living organism in the Solnhofen Lithographic Limestone in Bavaria, Gemany.

Horseshoe crabs are arthropods that have survived for than 300 million years. They are known to have lived even before the arrival of dinosaurs and have continued to survive for millions of years despite several changes to the land mass. 

While the fossil record has remained as an exhibit in the Wyoming Dinosaur Center in the US so far, researchers Dean Lomax of the Doncaster Museum and Art Gallery and Christopher Racay recently reconstructed and described the crab's final moments before its death.

According to the researchers, the ancient crab likely fell into an anoxic lagoon, where there was depletion of oxygen, some 150 million years ago.

They found that the trackway began unexpectedly, which suggested that the crab was thrown into the lagoon due to a storm. The arthropod is said to have continued its last walk despite low levels of oxygen in the lagoon.

However, the crab soon started facing the threat of losing its life, which the observers found based on erratic movements of the crab before it died at the end of the trackway. They revealed that the crab's tail begn moving up and down, a sign which showed that it was struggling during its last moments, reported the BBC.

"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 from University of Saskatchewan, Canada, who was not involved in the study, told the BBC.

"Discoveries such as this provide unique insights into the behaviour of extinct species - in this example during the last throes of its life and the environmental conditions that led to its demise," he said.

The findings of the study are published in the journal Ichnos.