| Summary: | This mural in the North Dakota Heritage Center depicts the forested swampland habitat that existed in western North Dakota about 60 million years ago. The huge crocodile Borealosuchus, turtles, and other animals and plants are shown in the swampland habitat. (Figure 11) heat, transformed into thick layers - as much as 30 feet - of lignite coal. Based on plant fossils, it has been determined that the climate was warm temperate to tropical, probably similar to areas in the southeastern United States today. During the early Paleocene, temperatures were mild on average about 50�F, and by the late Paleocene, the mean annual temperature has been estimated to be 65� F, with winter temperatures no colder than 55�F. This hot, humid and steamy swampy lowland also contained extensive forests that provided habitat for exotic plants and animals. Lush forests containing ferns, cycads, figs, Taxodium or bald cypress, Ginkgo or maidenhair free, Cercidiphyllum or katsura tree, Magnolia, Platanus or sycamore, Metasequoia or dawn redwood palms and other subtropical plants nourished in western North Dakota. Water lilies and Equisetum or horsetail grew in the ponds and swamps. Dense forests extended even as far north as the Arctic Ocean during this time. (Figure 11) Invertebrate animals, such as pill clams, mussels, snails, insects, and minute crustaceans, lived in the rivers, streams, ponds, and swamps. Many kinds of vertebrates also lived in and around these aquatic habitats. By the Paleocene Epoch, the last of the dinosaurs had become extinct. The primary predators were still reptiles, except now they were crocodiles, alligators, champsosaurs, and turtles. The largest of these animals, the crocodile Borealosuchus, was similar in appearance to the living crocodile and grew to lengths of 15 feet. (Figure 12) It was the main 18 201 1-2013 North Dakota Blue Book
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