Ancient anthropod with gnarly claws discovered in Burgess Shale
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21:08

Ancient anthropod with gnarly claws discovered in Burgess Shale

A B.C. fossil bed continues to be a treasure trove of discovery for Canadian scientists as another new species has been found.

The latest wonder in the Burgess Shale is a sea creature estimated to be 507 million years old which helps shed light on the evolution of claws found on many present-day species such as crabs, scorpions and millipedes.Twenty-one specimens of the new species — named Tokummia katalepsis — were found in the Marble Canyon site in Kootenay National Park by researchers from the Royal Ontario Museum and University of Toronto.

The discovery is detailed in a paper published Wednesday in the scientific journal Nature.

The fossils are exceptionally well-preserved arthropods, a group of invertebrate animals with segmented limbs and hard exoskeletons.

But the remarkable aspect of these fossils is that they show in detail for the first time the anatomy of early mandibulates — a subgroup with specialized pincers and claws used to grasp, crush and cut their food.

Mandibulates include millions of species and scientists say they are one of earth's greatest ecological success stories.

“In spite of their colossal diversity today, the origin of mandibulates had largely remained a mystery,” said Ce dric Aria, lead author of the study and a recent grad of the U of T who is now working in China.

"Before now we’ve had only sparse hints at what the first arthropods with mandibles could have looked like, and no idea of what could have been the other key characteristics that triggered the unrivalled diversification of that group.”

Although it may seem tiny at 10 centimetres when fully extended, the Tokummia was one of the largest predators of the Cambrian period.

And it may have led a terrifying reign with its large back claws and serrated front pincers that it likely used to capture soft prey hiding in the 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 added.

Cedric Aria (foreground) and other crew splitting layers of shale from the Marble Canyon quarry site in the hopes of revealing new fossils.

 It's believed the creature favoured tropical seas and was a bottom dweller, living much like lobsters are today.

It was covered by a two-piece shell and had subdivided limbs with tiny projections called endites.

Researchers now believe these endites were critical innovations in the evolution of legs and claws.

While interesting in its own right, the new fossil together with others from the Burgess Shale, form the base for all mandibulates.

"This story really is important for understanding the origin of one of the largest groups of animals on earth," said co-author Jean-Bernard Caron, senior curator of invertebrate palaeontology at the Royal Ontario Museum.

"It's basically a giant jigsaw puzzle out there and paleontologists only have access to a few pieces and every time you find a new piece you have a chance to complete a part of the puzzle. Sometimes you don't have enough piece and you're stuck for a long period of time... Finally here it's comforting to know that we can resolve it."

Caron first discovered the Marble Canyon deposit in 2012.

It's part of the larger Burgess Shale fossil deposit, which extends north into Yoho National Park.

As important as these sites are, Caron said it's important to find new deposits that connect the fossil record together.

"The story is not about the Burgess Shale. This story has worldwide implications. Here we're talking about the original mandibulates which are this super diverse group of organisms."

The public can tour the UNESCO World Heritage Site near Field, B.C., but must do so with a guide from either Parks Canada or the Burgess Shale Geoscience Foundation. Taking fossils from the site is prohibited.

source : Calgary SUN
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