Washington, Jan 29 : The origin of the horseshoe crab has been pushed back by at least 100 million years with the discovery of two nearly complete fossil specimens in Canada.
According to a report in Live Science, this finding has revealed a new genus of horseshoe crab called Lunataspis aurora, which roamed along the shorelines of the planet half a billion years ago.
The ancient horseshoe crab is estimated to have been just 1.5 inches (4 centimeters) from head to tail-tip. That's much smaller than its modern-day relatives that can span nearly 20 inches (50 centimeters), the report said.
"We do not know if the fossils were small because they were simply young animals or because Lunataspis just didn't grow any bigger," said researcher David Rudkin of the Royal Ontario Museum in Canada.
According to the report, David Rudkin of the Royal Ontario Museum in Canada and his colleagues made the discovery of the fossils of this species in 445-million-year-old rocks from the Ordovician period in central and northern Manitoba.
The specimens included patches of the animals' outer-covering and even evidence of their compound eyes.
Horseshoe crabs are not true crabs and are instead more closely related to spiders and scorpions. Like their eight-legged relatives, horseshoe crabs sport a flexible exoskeleton made of chitin rather than the hard-shell armoring worn by crabs.
Analysis of the recent finds also indicates the ocean creatures haven't changed much over the eons.
"We wouldn't necessarily have expected horseshoe crabs to look very much like the modern ones, but that's exactly what they look like," said Rudkin.
"This body plan that they've invented, they've stayed with it for almost a half a billion years. It's a good plan," Rudkin told LiveScience. "They've survived almost unchanged up until the present day, whereas lots of other animals haven't," he added.
Whereas major extinction events have wiped even the mightiest, non-avian dinosaurs from our planet, this primitive-looking organism has come out unscathed.
"The horseshoe crab, the lowly little animal that crawls out of the sea every once in a while to mate, it's survived for at least 445 million years in more or less the same form," said Rudkin.