The Earth has experienced many dramatic changes in climate since the dinosaurs¹ went extinct 66 million years ago. One of the warmest periods was the early Eocene Epoch², 50 to 53 million years ago. During this interval³, North American mammal communities were quite distinct from those of today. This is illustrated⁴ by a study published in the latest issue of the Journal of Vertebrate Paleontology that describes an ancient hedgehog（刺猬） and tapir（獏） that lived in what is now Driftwood Canyon⁵ Provincial⁶ 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 geographic⁷ 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（迄今） 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 jaw⁸ 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 rhinos¹⁰ with no horns and a short, mobile, trunk or proboscis¹¹（鼻子）.

 

"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 intriguing¹² 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 kin⁹ are good indicators¹³ of dense¹⁴ forests and high precipitation," said Eberle.

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