University of Toronto researchers discover 507-million-year old sea creature

Insects and other crawlies might not be the most pleasant creatures to some, but they are the most abundant organisms on Earth. Now a 507-million-year-old fossil has been discovered by Canadian researchers that is shedding light on their evolution.

Researchers at the University of Toronto collected the tiny fossil during a 2014 expedition to Marble Canyon in the Burgess Shale in British Columbia. What they didn't know at the time was that they had found a species that would help them establish links with other mandibulates — creatures with a pair of appendages called mandibles designed to crush and cut any food.

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This newly discovered species, called Tokummia katalepsis, lived during the Cambrian period, when Canada had a climate far different than it does today. At the time, Tokummia would have lived in a tropical sea, full of other marine creatures as life began to flourish. It would have lived on the bottom of the sea floor, using its many legs to walk and occasionally swim.

However, Tokummia wasn't restricted to the sea: the researchers believe it would have been able to live on the land as well, where it could prey upon other creatures.

But most important are Tokummia's mandibles. These arm-like appendages would have been used to crush food and bring it to its mouth. 

"The pincers of Tokummia are large, yet also delicate and complex, reminding us of the shape of a can opener, with their couple of terminal teeth on one claw, and the other claw being curved towards them," said Cedric Aria, lead author of the study that appeared in the journal Nature.

It's believed the mandibles may have been too delicate to handle shelled animals, and it's likely Tokummia ate soft animals hiding in mud. 

"Once torn apart by the spiny limb bases under the trunk, the mandibles would have served as a revolutionary tool to cut the flesh into small, easily digestible pieces," Aria said. 

Connecting the dots

Co-author Jean-Bernard Caron of the Royal Ontario Museum said that the discovery is an important step in linking other species together. 

"One thing that is quite interesting is that we've had fossils from the Burgess Shale that we now know are related to Tokummia," he said. "One animal, Canadaspis, named after Canada, has remained a mystery even though thousands of specimens have been found in the Burgess Shale. But now we are able to link this animal to this group of mandibulates."

Caron said that the discovery was also very special because it was so well-preserved, with soft body tissue. And though Tokummia measures just 10 centimetres, he called it a "giant" compared to most others found in the area, which can measure just a few centimetres.

Caron said Canada provides unique opportunities to unravel the mysteries of how life evolved, something for which he's grateful.

"In Canada, we are blessed in many ways, by absolutely stunning fossil deposits which really tell us the story of life, in ways that no other countries in the world can tell," he said.