During the early Eocene epoch, North American mammals were quite different from what we see today. Here's one example: researchers have just uncovered a 2-inch-long fossilized hedgehog in British Columbia. That's the size of your thumb.
It's the tiniest hedgehog known to science. The researchers, writing in the most recent issue of the Journal of Vertebrate Paleontology, named the critter Silvacola acares, which translates to "tiny forest dweller."
Above: The proto-tapir Heptodon takes a drink, while the small hedgehog Silvacola acares stalks a green lacewing in the foreground. Copyright Julius T. Csotonyi, used with permission.
At the LA Times, Deborah Netburn describes the creature:
This little guy was so eensy-weensy that that his back molars were just 1 millimeter in length. His bones were so delicate that the researchers were worried his fossil would break apart if they tried to get it out of the rock.
Instead, they decided to leave the fossilized parts of the animal's skull embedded in the rock and do a micro-CT scan on it to figure out exactly what mammal they were looking at.
"I compared the scan of his molars to hundreds of little, tiny teeth," said Jaelyn Eberle, who studies ancient mammals at the University of Colorado at Boulder. "But before too long I realized there isn't anything that looks exactly like this guy's teeth."
Thanks to its unusual teeth, Eberle realized she didn't just have a new species of hedgehog, but an entirely new genus.
Along with the hedgehog, Eberle's team also uncovered a new early tapir which they called Heptodon. Modern tapirs look something like tiny rhinos, but in the place of the horn, they have an elephant-like trunk or proboscis. Heptodon doesn't have the trunk, and its about half the size of its modern descendents.
What's special about the fossil find is that today's tapirs live in the tropics, not in the Great White North. Given the fossil plants that were found nearby, the find lends support to the idea that tapirs are a good indication of habitats characterized by dense forests and lots of rain. Paleontologists of the future who find fossil tapirs can therefore make certain predictions about the local environment more generally.
David Greenwood, a co-author of the study, explained to the Society of Vertebrate Paleontology that "Driftwood Canyon [where the fossils were found] is a window into a lost world - an evolutionary experiment where palms grew beneath spruce trees and the insects included a mixture of Canadian and Australian species. Discovering mammals allows us to paint a more complete picture of this lost world."