Making of North America Part 3

1. In an empty corner of lies a very special place. It is a remote region called the Kaiparowits Plateau. This area contains an important story of the history of life in North America. Professor Kirk Johnson is with paleontologist Joe Sertich. This area is jam packed with ______fossils. A trick of Professor Johnson to tell if a rock is a piece of bone is to see if it sticks to his ______. They have with them the cast of the skull of a that Joe helped identify and name. From the teeth you can easily tell it is a ______eater. This dinosaur is called Lythronax which means the “king of ______.” Lythronax looks a look like the more famous ______, but it is 10 million older. 80 million years ago, all of North America was home to such creatures of as Lythronax. More than a ______of all the ever found have been found in North America. 2. Before life was found on land, it existed in the sea as far back as 3.5 billion years. A connection to this early life is found in the Bahamas. Professor Johnson is there to see a rare living fossil. They are looking for one of the oldest organisms on the planet. After diving down 20 feet, they find the organisms they came to see; and it is the ______. These are called stromatolites, and they are alive. A thin layer of ______(actually cyanobacteria) forms a somewhat sticky mat where mud and sand collects until a mound is built up. Today living and growing stromatolites are extremely ______. In the Bahamas, these living mounds are often covered completely with sand by the strong currents, and later the currents will uncover them. This keeps plants and corals from growing on them and such things as snails from feeding on them. They didn’t have competition and predators billions of years ago. They were one of the dominant organisms in Pre- seas for maybe ______percent of Earth’s biologic history. They are the earliest fossilized form of life we have found. 3. During the early Pre-Cambrian, Earth’s atmosphere was very different than today. Most organisms today would suffocate under these early atmospheric conditions. However the cyanobacteria of the stromatolites could thrive under those atmospheric and oceanic conditions, and these bacteria developed a biological chemical reaction that used carbon dioxide and water and released ______. This reaction is called photosynthesis. Over the course of ______years, stromatolites pumped out so much oxygen that the atmosphere changed into one that could support modern types of organisms. Modern organisms developed biological chemical reactions that can use (or consume) oxygen. It is thought from the rock record that about ______million years ago complex oxygen consuming life forms really took off. One such form of life, considered a primitive , were the ______. Later came the jellyfish types known as Cnidaria. These had nerves and muscles. Finally about ______million years ago dinosaurs appeared. 4. But what was it that allowed so many different types of dinosaurs to thrive here in North America. One clue can be found in the center of U.S. on the Great ______of central North America. Professor Johnson next takes us to Monument Rocks in ______. These rocks are made of chalk. Professor Johnson says that just 1 inch of this chalk represents ______years of deposition. This land is full of amazing fossils. Two people, Chuck Bonner and Barbara Shelton, have spent years finding and studying the fossils here. They showed Professor Johnson an 80 million--old marine fish named Xiphactinus which was ______feet long. About 130 million years ago much of North America was covered by a great inland sea. The coastlines around this inland sea produced a variety of habitats for dinosaurs. But 70 million years ago something dramatic began to happen; the inland sea began to ______away. 5. To explain what happened to this great sea, Professor Johnson next heads for Colorado. High up in the Rocky Mountains he finds what locals call “ baths.” But they are actually the fossil of ancient ______known as ammonites. This animal had a spiral, chambered shell with a fleshy head and tentacles at the open end. Its body plan was something like a ______or octopus to which it was related. The location of these fossils is west of Denver and over 7,700 feet above sea level. This elevation of the fossils is a consequence of plate tectonics. As this region rose the sea drained away leaving sea creatures high and dry. This was a very slow process as it is today. However not all biologic change happens slowly. To help us understand this, Professor Johnson is headed north to North Dakota and its ______-lands. 6. The rock here is known as the Hell Creek Formation which is a 300 foot-thick layer of rock that stretches over ______states. Much of the rock here is soft with charcoal from ancient fires. Professor Johnson is searching for a particular layer that is ______million years old. This important, ancient layer is a little rusty-orange sediment zone. This rusty colored zone may not look like much, but represents an Armageddon. The layer contains little round balls about a millimeter in diameter. These balls used to be ______beads. What could cause the formation of these glass beads? Something must have melted rock and tossed the melted globs up through the air to rain down on the landscape as glass beads. Perhaps the cause was a volcanic eruption. But the answer must be different because of what else is in this layer, tiny crystals of ______quartz. 66 million years ago and asteroid (some think comet) the size of ______hit Earth with the power of a billion atomic bombs. Above the layer with those glass bead and shocked quartz there are no ______fossils, only crocodile, turtle and bird fossils. This was an ecosystem-wide extinction event, with losses of half the of plants and ______. One group that managed to hang on was the , most of which at this time were small burrowing .