Stephanie Pierce was strolling down a beach on Cape Breton Island this summer when she happened to 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.”
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…