New Burgess Shale fossils shed light on the evolution of bigness


It was late, and a team of paleontologists excavating an unexplored outcrop of the Burgess Shale was ready to call it a day. The camera crew filming the excavation in Kootenay National Park had already packed it.

Next, one of the team members split and opened a large shale plate.

“I remember gasping here and there,” said Joe Moisshuk of the Royal Ontario Museum.

“Everyone was running to see what was found. It was clearly a new animal.”

The 2018 excavation revealed that it was also prominent in the strange world of the Burgess Shale, a 500-million-year-old rock outcrop in the Canadian Rockies, British Columbia, packed with early fossils. increase. The days of complex life on earth.

Most of those fossils are the size of the little finger. This is not it.

“We found this huge shell,” recalled Moysiuk.

“The total length of the animal must be at least 50 cm. This is arguably one of the largest animals we have known since the Cambrian period.”

Titanokorys gainesi was a time before life on land, where the ocean was a huge laboratory for evolution and a huge laboratory for unraveling the answers that plants and animals still use today. Was born from. Spinal cord, eyes, exoskeleton—all of which first appear in the Cambrian period.

“All the body plans of the major animals evolved first,” says Moysiuk.

“We see the first representatives of what looked like fish, insects and crabs. The other animals you might dream of were probably Cambrian relatives.”

Titanokorys is not remote and familiar.

“These things look very alien,” Moysiuk said.

The entire beast was flat and rectangular, with a gill slit at the back, a horseshoe-shaped plate protecting the head, and an armor plate underneath. The eyes were probably on the stem, in the middle of the body. There was a rake-like growing claw on the front.

Predators, it probably cruised the ocean floor looking for any delicious bit it could wipe out in its mouth.

“The mouth itself is really cool,” Moysiuk said. “It looks like a pineapple slice lined with these sharp, inward-looking teeth.”

Burgess Shale fossils are famous not only for their age but also for their preservation. You can see soft body parts such as eyes well. The creature’s last meal is sometimes stored on rocks.

Even for Burgess, Titanokorys are well preserved.

“We have relatively complete ruins,” Moysiuk said. “These fossils are very rare.”

Fossils will allow paleontologists to study some of the most basic questions of evolution, he said. For example, why do some animals grow and others don’t?

“This seems to be related to this evolutionary arms race that took place in the Cambrian period, where more and more animals are trying to beat each other in size,” Moysiuk said. “As a predator, being quite big benefits you.”

But whatever the final result of the Titanokorys study, Moysiuk said there was nothing comparable to the thrill of seeing the fossil emerge from the dark shale of Burgess hundreds of millions of years later.

“It was one of those moments I would never forget.”

Canadian press