Coryphodon, Eocene Epoch

To launch Stamp Month 1994, the fourth and final set in the Prehistoric Life in Canada series is being issued on September 26, 1994. Mammals appeared about 190 million years ago, and became dominant after extinction of dinosaurs some 65 million years ago. Mammals are warm-blooded, hairy animals with backbones, possessing four-chambered hearts and diaphragms to help breathing. Most give birth rather than laying eggs, and all feed their young from milk-producing mammary glands unique to the class Mammalia. The four depicted here are long since extinct. A large tapir-like, short-legged mammal weighing about 500 kilograms, Coryphodon was about one metre at shoulder height and 2.3 metres long. Although it had a large skull with canine tusks like those of a hippopotamus, its brain at 90 grams was very small - one of the smallest brain/body weight ratios known among mammals. A browsing animal, Coryphodon probably had semi-aquatic habits like today's hippo, feeding on roots, tubers and aquatic plants. Widespread in North America between 59 and 51 million years ago, this large mammal ranged from Ellesmere Island in the north to Mississippi, Texas and New Mexico in the south. Both plant and vertebrate fossils from Ellesmere Island, Canada's most northerly island, indicate that Coryphodon lived there in a warm temperate climate along with small alligators, soft-shelled turtles and horse-like mammals. This set concludes the Prehistoric Life in Canada series begun in 1990 with four stamps featuring early life forms that dwelled in the water. The second set in 1991 recalled "The Age of Primitive Vertebrates", with two early marine creatures, a land reptile, and an early tree. Last year's set, "The Age of Reptiles", featured three dinosaurs and a marine reptile.