Researchers from the University of Colorado in Boulder have said a nearly 52-million-year-old fossil is that of the tiniest hedgehog to have ever lived on Earth.

According to the researchers, the prehistoric hedgehog, named “Silvacola acares,” is a new genus and species and measured only about 2 inches long, which is smaller than the length of an average adult thumb. 

“It is quite tiny and comparable in size to some of today’s shrews,” Jaelyn Eberle, an associate professor at CU-Boulder and the study’s lead author, said in a statement, referring to the hedgehog fossil.

Eberle speculated that Silvacola might have fed on insects, plants and seeds. However, she was not sure if it had quills like contemporary hedgehogs do.

“We can’t say for sure,” Eberle said. “But there are ancestral hedgehogs living in Europe about the same time that had bristly hair covering them, so it is plausible Silvacola did too.”

According to the study, published in the Journal of Vertebrate Paleontology on Tuesday, after the dinosaurs died out 66 million years ago, the Earth experienced an extremely warm period called the Early Eocene about 53 million to 50 million years ago, during which period, North American mammal communities were quite distinct from the ones that exist today.

“Today's hedgehogs, and especially the ones that are kept as pets, are considerably larger,” Eberle told Reuters. “The smallest living hedgehogs are about 4 to 6 inches (10 to 15 cm) long, not including the tail, but the moonrats (close cousins) can actually be upwards of 18 inches long (46 cm) and weigh a few pounds.”

Scientists also discovered fossils of a tapir-like mammal about the size of a medium-sized dog at a site in north-central British Columbia, known as Driftwood Canyon Provincial Park, which likely was a rainforest when these animals roamed there. The creature, researchers said, was a herbivore about half the size of today's tapirs. However, it lacked the short trunk that these mammals usually have.

According to scientists, most of the fossil-containing rocks at Driftwood Canyon were formed on the bottom of an ancient lake and are well-known for their exceptionally well-preserved leaves, insects and fishes. But, this is the first time that fossils of mammals have been identified at the site.

“Driftwood Canyon 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,” David Greenwood, a professor at Canada’s Brandon University, said in the statement.