This is a reconstruction of the early Eocene (52 million-year-old) fauna that inhabited the rainforest around a northern British Colombia lake. The tapiroid Heptodon drinks in the shallows, while the small proto-hedgehog Silvacola acares stalks a green lacewing (Pseudochrysopa harveyi) in the foreground. Julius T. Csotonyi
If you peered through the undergrowth of the B.C. rainforest 50 million years ago, you might spot some unusual mini mammals, including a thumb-sized hedgehog and a tapir no bigger than a springer spaniel.
Paleontologists are excited about the recent discovery of fossil jaws from those two species in northern B.C.'s Driftwood Canyon Provincial Park. They are the first mammals ever identified in Canada south of the Arctic from the early Eocene epoch, around 53 million to 50 million years ago.
"We're filling a massive gap in knowledge," said David Greenwood, a paleontologist at Brandon University in Manitoba who co-authored a study describing the discovery, published today in the Journal of Vertebrate Paleontology.
The hedgehog is a brand new species, and possibly one of the smallest hedgehogs ever. The animal, which was no longer than six centimetres when fully grown, has been given the scientific name Silvacola acares, which means "tiny forest dweller."
"They were really tiny, smaller than a house mouse," said Natalia Rybczynski, a paleobiologist at the Canadian Museum of Nature in Ottawa, who co-authored the paper.
While the anatomy of its teeth shows that it was a hedgehog relative, it likely didn't look like modern hedgehogs, she added.
"If we saw them in a zoo, we wouldn't be like, 'Oh, that's a hedgehog,' " she said. "This little guy, he might not have had the spines of hedgehogs you see today."
Many early hedgehog relatives also had longer tails than the stubby tails of modern hedgehogs, she added.
Likewise, the early tapir relative was quite different from the modern version found in the Amazon rainforest of South America, said Jaelyn Eberle, curator of fossil vertebrates the the University of Colorado Museum of Natural History and lead author of the study.
The B.C. tapir was likely half the size of modern tapirs, which can grow bigger than a large pig. It likely didn't have the modern tapir's long nose and probably had longer legs relative to its body, based on more complete fossils of other related tapirs from the same genus, Heptodon, that lived around the same time.
Tapir may be new species, too
Eberle said the B.C. tapir appears to be slightly larger than other tapirs found in North America from the same time period, and could be a new species. But the fossil is too small a fragment and too poorly preserved to say for sure.
Driftwood Canyon has been known for decades as an early Eocene fossil site rich in an odd mixture of plants that ranged from palms to spruce trees, along with insects and fish. The steamy Eocene epoch started 13 million years after the extinction of the dinosaurs, when the entire Earth was quite a bit warmer than it is today. However, Greenwood said, Driftwood Canyon itself was on an elevated plateau, so it was likely cooler than the surrounding lowlands, and may even have experienced the occasional frost or snow in the winter.
Greenwood was excavating plant fossils from the cliffs at the site in 2010 when then-undergraduate student Megan Gilbert called out that she had found a jaw.
It was an astonishing discovery given how tiny the fossil was.
"It's the size of a little fingernail," Greenwood recalled of the hedgehog discovery, noting that Gilbert had an unusually good eye for mammal fossils.
The tapir fossil was discovered by a student from the University of Utah who was digging in a coal seam for geochemical samples.
"As his pick axe descended, he shouted, 'There's a jaw!' And unfortunately, a piece of the jaw got mashed and sent down into the river," Greenwood said.
But part of it remained intact, and it contained teeth — the part of the skeleton in mammals that can be used to figure out what kind of animal it was.
The two fossils were identified by Eberle as parts of a hedgehog and a tapir.
The identification was a challenging exercise, particularly in the case of the hedgehog.
The fossil was extremely tiny, embedded in a piece of rock, and was cracked down the middle. It was less than a centimetre long, and it contained five teeth.
"They're tiny, and most of them are split in half," Rybczynski said. "You can't take them out mechanically."
In the past, she said, the specimen would have been impossible to study.
But she decided turn to modern technology. She sent the fossil to Penn State University to undergo high-resolution CT scanning, which is increasingly used to study fossils embedded in rock.
She then turned to Alex Tirabasso, an Ottawa animator who normally works for the film and TV industry. He took the image data from the scan and managed to digitally put the pieces of the fossil back together into a 3D computer model, which was sent to Eberle.
After months of comparing it to other mammal fossils, Eberle confirmed it was a new species of hedgehog.
Eberle is now eager to head back to Driftwood Canyon to hunt for more mammal fossils from the early Eocene — a period of time that many paleontologists find particularly interesting because it could provide clues about what our world could be like in coming centuries if it continues to warm as a result of human-caused climate change.
"The timing is just perfect for understanding this global warming, where we didn't have any data before," she said. "I think there's a lot more in this neck of the woods that just hasn't been looked at yet."
The fieldwork done by Greenwood's team to discover the fossils was funded by the Natural Sciences and Engineering Research Council of Canada. Greenwood said he is also interested in doing more excavations at Driftwood Canyon, but his funding from the council was not renewed this year.
Other support for the study came from the University of Colorado and the Canadian Museum of Nature.