Harvard team's Cape Breton fossil find could shed light on our fish-like ancestors

Stephanie Pierce was strolling down a beach on Cape Breton Island this summer when she happened pick up a rock, simply because it looked “interesting.”

That single stone would lead the Harvard University paleotologist and her small team on a hunt along the boulder-strewn stretch near Sydney Mines, one that would turn up a previously undiscovered fossil bed that could shed new light on some of the earliest ancestors of amphibians, reptiles and mammals — including humans.

Some of the fossils were embedded in heavy, dense rock the team carted out of the area as they kept a wary eye on the rising tide and eroding cliff face above them.

“One of the boulders that we took out — I mean it took four of us about four hours to walk it about half a mile. It was very heavy,” said Pierce. “It was a little bit dangerous.”

Acanthostega, an early tetrapod from East Greenland

Early tetrapods like this one, called acanthostega, were fish-like. They had tail fins, gills and up to eight fingers. (Richard Hammond)

The fossils are of primitive land animals called tetrapods. Early tetrapods came from some of the first creatures to crawl out of the prehistoric oceans and proliferated during the Carboniferous Period, about 360 million years ago.

“Anything that has four limbs with fingers and toes is a tetrapod,” said Pierce, who is curator of vertebrate paleontology at the Museum of Comparative Zoology at Harvard. “So you are a tetrapod — all humans are tetrapods.”

Tim Fedak, director and curator of the Fundy Geological Museum in Parrsboro, N.S., said early tetrapods had short, stumpy legs and retained many fish-like characteristics, including a tail fin.

“They were actually quite small, sort of a metre long would be a fairly large animal,” he said.

Why these fossils are rare

Fast forward about 30 million years and tetrapods had become well-adapted to living on land, and had grown longer legs that could hold the body off the ground, said Fedak.

But fossils from the beginning of the Carboniferous Period until about 315 million years ago are rare and are known in the fossil record as Rommer’s Gap, named after paleontologist Al Rommer who first wrote about it.

There was a mass extinction and little is known about what happened to tetrapods during that time, according to Pierce.

The search for fossils to fill that gap is what drew her four-person team to Nova Scotia for four weeks in June and July.

Pierce said Carboniferous-era rocks are found all over the world but what makes Nova Scotia unique is that the rocks — and the fossils preserved inside — are accessible.

“It has got lots of beaches and lots of cliffs — a lot of that Carboniferous rock is actually outcropping there and a lot of those fossils are actually falling out of those cliffs,” said Pierce.

In fact, the only other area where you find the early Carboniferous rock with fossils exposed is in Scotland.

harvard fossil team

The team prepares to move a heavy fossil from the beach. (Courtesy of Stephanie Pierce)

There are three places in Nova Scotia where these rocks are found: Parrsboro, Blue Beach outside Wolfville, and parts of Cape Breton.

“There’s really big tides and that constantly erodes the beaches, which gives us access to all these fossils and so you don’t have to wait 20 years for new rock to be exposed,” said Pierce.

“It’s actually being exposed every single day with every single tide coming in and every single tide going out.”

Usually, tetrapod fossils are found either in coal seams or within the remains of fossilized trees — likely because some of our earliest ancestors were small and tended to hide or live in trees.

Which makes the newly discovered fossil bed on the beach near Sydney Mines so unusual.

harvard fossil team

Chris Capobianco inspects a fossil on Blue Beach near Wolfville, N.S. (Courtesy of Stephanie Pierce)

This week, members of Pierce’s team are driving back to Nova Scotia to pick up the specimens. The fossils will then be prepared and studied before being returned to Nova Scotia for display.

“They’re definitely large tetrapods. They could be early amphibians, they could be early mammals,” Pierce said. “It’s definitely something new for Nova Scotia paleontology.”

Every fossil is unique, she said, and the delicate process of extracting fossils can take anywhere from a few weeks to a few years.

harvard fossil team

Moving fossils from remote spots like this Nova Scotia beach can be a tough slog. (Courtesy of Stephanie Pierce)

What to do if you find a fossil

If you happen to find a fossil on a Nova Scotia beach, both Pierce and Fedak say to leave it in place and take photos both up close and a further away. Where the fossil is found gives important information about how the animal lived and died.

“If a fossil happens to be on the beach where it might be very difficult to locate it again, things might move, it would make sense to bring it to the museum if they have a question,” said Fedak.

All fossils found in Nova Scotia belong to the province and the Nova Scotia Museum is the official caretaker of these specimens.

Source link