| Summary: | Flowing water from the glaciers also deposited outwash sands and gravels. Three- fourths of North Dakota is veneered with glacial deposits in all but the southwestern corner of the state. In some areas it is more than 400 feet thick. Fossils of the cold- adapted animals that lived in North Dakota during the Pleistocene Epoch are found in these glacial deposits. The most impressive were the large mammals, including mammoths, mastodons, giant bison, ground sloths, and horses. Most of these large mammals became extinct at the end of the Pleistocene about 13,000 years ago. Fossils, particularly teeth, of woolly mammoths, are fairly common in North Dakota. (Figure 22) And yet, complete skeletons of this animal have eluded discovery in this State. Known as Mammuthusprimigenius, woolly mammoths were migrants from Eurasia across the Bering land bridge. Woolly mammoths are in the same family as modern elephants. They were relatively small for a mammoth, growing to heights of about nine feet. As with today's elephants, their upper incisors were greatly elongated to form tusks. These recurved tusks were used for brushing away snow, digging up roots, debarking frees, and fighting. They also had digit-like projections at the end of their trunks for grasping. Woolly mammoth teeth were huge, some over a foot long, and flattened and were used for grinding vegetation, mainly grasses. They had a thick coat of shaggy, black to brown hair for insulation against the severe climate, as well an undercoat of fine hair and a layer of fat to help stay warm. Because frozen carcasses of these animals have been found in Siberia, much is known about the anatomy of woolly mammoths. Early people hunted them for food and clothing, constructed dwellings out of their bones in Siberia, and painted and etched images of them on cave walls in France and Spain. They also became extinct about 13,000 years ago, except for a small group of dwarf mammoths on an Arctic island that survived until about 6,000 years ago. Fossils of the larger mammoth, the Columbian mammoth Mammuthus columbi, have also been found in North Dakota. At the end of the Pleistocene Epoch, the American mastodon, Mammut americanum, was one of the most common proboscideans that lived in North America. Few fossils of these animals have been found in North Dakota. (Figure 23) Unlike the woolly mammoth, a recent migrant from Eurasia, the mastodon had been a resident of North America for millions of years. Mastodons were elephant- like and elephant-sized - about as large as the Indian elephant that lives today, but they were not true elephants and were not too closely related to mammoths. Adults were about 10 feet tall at the shoulder. The heads of these animals were long and held low, with long, curved tusks. They probably used their tusks to break branches and bark from trees. Because one tusk is usually shorter than the other, from wear it can be determined if the animal had a right- or left-tusk preference. Like the woolly mammoth that lived in North Dakota at the same time, mastodons were covered with long, shaggy hair for insulation against the cold. Mummified specimens indicate that they had brownish coarse outer hair with a fine woolly undercoat similar to semi-aquatic animals like moose. They were browsers and lived Chapter One - History of Ancient Life in North Dakota 33
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