The Earth has experienced many dramatic changes in climate since the dinosaurs went extinct 66 million years ago. One of the warmest periods was the early Eocene Epoch, 50 to 53 million years ago. During this interval, North American mammal communities were quite distinct from those of today. This is illustrated by a study published in the latest issue of the Journal of Vertebrate Paleontology that describes an ancient hedgehog and tapir that lived in what is now Driftwood Canyon Provincial Park, British Columbia, some 52 million years ago.
"Within Canada, the only other fossil localities yielding mammals of similar age are from the Arctic, so these fossils from British Columbia help fill a significant geographic gap," said Dr. Natalia Rybczynski of the Canadian Museum of Nature, a co-author of the study. Other fossils of this age come from Wyoming and Colorado, some 2,700 miles to the south of the Arctic site of Ellesmere Island.
The ancient hedgehog is a species hitherto unknown to science. It is named Silvacola acares, which means "tiny forest dweller," since this minute hedgehog likely had a body length of only 2 to 2.5 inches. The delicate fossil jaw of Silvacola was not freed from the surrounding rock as is typical for fossils. Rather, it was scanned with an industrial, high resolution CT (computed tomography) scanner at Penn State University so it could be studied without risking damage to its tiny teeth. Modern hedgehogs and their relatives are restricted to Europe, Asia, and Africa.
The other mammal discovered at the site, Heptodon, is an ancient relative of modern tapirs, which resemble small rhinos with no horns and a short, mobile, trunk or proboscis.
"Heptodon was about half the size of today's tapirs, and it lacked the short trunk that occurs on later species and their living cousins. Based upon its teeth, it was probably a leaf-eater, which fits nicely with the rainforest environment indicated by the fossil plants at Driftwood Canyon," said Dr. Jaelyn Eberle of the University of Colorado, lead author of the study.
Most of the fossil-bearing rocks at Driftwood Canyon formed on the bottom of an ancient lake and are well-known for their exceptionally well-preserved leaves, insects, and fishes. But no fossils of mammals had ever before been identified at the site. The fieldwork that resulted in these discovered was supported by Natural Sciences and Engineering Research Council of Canada.
"The discovery in northern British Columbia of an early cousin to tapirs is intriguing because today's tapirs live in the tropics. Its occurrence, alongside a diversity of fossil plants that indicates a rainforest, supports an idea put forward by others that tapirs and their extinct kin are good indicators of dense forests and high precipitation," said Eberle.
Fossil plants from the site indicate the area seldom experienced freezing temperatures and probably had a climate similar to that of Portland, Oregon, located roughly 700 miles to the south.
"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," said Dr. David Greenwood of Brandon University, a co-author of the study. "The early Eocene is a time in the geological past that helps us understand how present day Canada came to have the temperate plants and animals it has today. However, it can also help us understand how the world may change as the global climate continues to warm."
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