230 240 240 2 250 2 250 220 220 210 2 200 190 190 180 180 70 17 160 150 1 140 1 140 130 130 130 120 120 110 1 100 90 80 70 60 Triassic world Ju Ju urassic world urassic orld 65 14 45 45 5 5 21 13 2 24 48 A single, arid continent called Pangaea existed, over which animals migrated freely. Great water-filled rift valleys formed. Sea levels rose. Pangaea split into several large fragments, though significant contact remained especially in the south. A narrow Atlantic Ocean formed. A warm, lush climate covered the Earth. End of an era 65 million years ago, well over half of all animals and plants on land and sea perished. A leading theory is that a large meteor slammed into Mexico at that time, triggering crippling dust, de- bris, earthquakes and volcanic activity. Dinosaurs became extinct. Mammals, the size of rodents at the time, grew to prominence. Continents moved rapidly toward current positions. Contact was regained between Asia and North America across the Bering Strait. Late Campanian age shoreline (79-72 million years ago) Twin Cities Western Interior Seaway Coastal plain Coastal plain Alluvial plain Volcanic deposits Highlands Early Campanian age shoreline (83.5-79 million years ago) Source: ESRI Dave Silk/Star Tribune MONTANA Sources: ESRI, GDT, USGS, BLM Jane Friedmann/Star Tribune 2 2 87 89 191 287 87 89 15 Dinosaur country in Montana’s badlands Towns near sites where dinosaurs have been discovered. wn B u d Upper Missouri River Breaks National Monument Charles M. Russell National Wildlife Refuge MONTANA The badlands of the Upper Missouri River Breaks in Montana today are among the most desolate areas in North America, with rattlesnakes in waist-high brush and coyotes roaming the hills. But 75 million years ago, when dinosaurs ruled the world, they were host to a lush, semitropical landscape teeming with life. For the first time in more than 150 years, researchers have gone dinosaur hunting in the bowels of the Breaks in an effort to recreate that world. Already, two large duck-billed dinosaur bones have been extracted, and in coming years giant bones or new species might be uncovered. The hope is that the dig, conducted by the Science Museum of Minnesota and Macalester College, will help answer what happened to the dinosaurs and why. 1. Spray on liquid preservative to harden the bone and protect it. 2. Remove as much rock as possible to lessen weight without jeopardizing the fossil. 3. Dig a trench underneath the specimen, forming a “pedestal” and leaving the fossil atop a slice or “mushroom” of rock. 4. Wrap wet paper towels around the exposed bone to keep plaster from sticking. 5. Wrap burlap strips soaked in wet plaster of paris around the specimen until a “jacket” or cast is formed. Allow the cast to harden. 6. Chip away pedestal base and flip over jacketed bone. Cover the underside of the specimen with a jacket of plaster of paris to completely encase the piece. 7. Give the specimen an inventory number and transport it to laboratory. Saw away jacket. 8. Carefully separate remaining rock from the fossil using tools such as small chisels, dental picks, brushes and com- pressed air. JURASSIC PERIOD – AGE OF GIANT DINOSAURS 213-145 million years ago Huge dinosaurs such as Apatosaurus and Allosaurus walked the land amid lush forests. Flying reptiles called Pterosaurs ruled the skies. The first true birds branched out from a small reptilian ancestor. Marine reptiles, invertebrates and plankton navigated the seas. CRETACEOUS PERIOD – DINOSAURS FLOURISH 145-65 million years ago The largest dinosaur population may have lived during this period. Horned dinosaurs such as Triceratops and Centrosaurus appeared. The armored ankylosaurs, duck-billed hadrosaurs and large carnivorous tyrannosaurids, such as Tyrannosaurus rex, were a few of the quickly evolving dinosaurs. Birds became increasingly numerous and flowering plants emerged. By the end of the Cretaceous peri- od all dominant large and small reptiles, except the crocodile, were extinct. A replica of the skull of “Sue,” the largest, most complete Tyrannosaurus rex skeleton ever unearthed. The 7-ton, 42-foot-long dinosaur was discovered in the South Dakota Badlands in 1990. JURASSIC EARTH-SHAKERS Apatosaurus was a sauropod about 70 to 90 feet long. It weighed about 66,200 lbs. This four-footed plant-eater was once known as Brontosaurus. THE RISE AND FALL OF THE DINOSAUR Tom Sweeney/Star Tribune Tom Sweeney/Star Tribune Photo by Greg Helgeson Majungatholus atopus, a 30-foot dinosaur that lived in the late Cretaceous period in what is now Madagascar, has recently been found to have been a cannibal. WHERE THE DINOSAURS ROAMED Daspletosaurus “frightful flesh-eating lizard” First identified: 1970 Length: 26-33 ft. Weight: 4,400-7,700 lbs. Time period: 78 to 68 million years ago Places found: Montana, Alberta Cousin to the Tyrannosaurus, it was a fearsome carnivore with a heavy skull and strong jaws lined with dagger-like teeth. It probably ran on its hind legs while hunting with jaws open, sinking its teeth into prey and locking its jaws shut. It may have used the large, curved claw on the second digit while attacking. Stegoceras “roof horn” First identified: 1902 Length: 6.5-9 ft. Weight: 122 lbs. Time period: 86 to 68 million years ago Places found: Montana, Alberta Stegoceras, a rather speedy herbivorous dinosaur walked on its hind legs and shredded plants with its slightly curved and serrated teeth. The thick, domed skull was once thought to be used for “head- butting.” Recent research has cast doubt on that theory. FROM THE DIG TO THE MUSEUM FLOOR The most important, and delicate, part of a dinosaur dig is preparing the fossils for transport. Here is the process paleontologists follow: Telegraph Creek Formation (variable) A transitional layer from shales below to sandstone above. Hell Creek Formation (700 feet) The uppermost, latest layer of sediment formed during the Cretaceous period is named for exposures studied in Hell Creek, near Jordan, Montana. The top consists of carbon deposits amid fossil- filled sandstone and shale layers. Dinosaur fossils have been found in the massive sandstone portion at the base. Triceratops fossils and the fossils from which Tyrannosaurus rex was named were found in this layer. Judith River Formation (250-500 feet) Layered sandstone, dark shale and light- colored sandy shale. Freshwater deposits often occur, especially toward the top. At both top and bottom of the formation, hogback slopes tend to form, created when softer sandstone erodes, leaving a tougher, sloping layer exposed.This formation is rich in dinosaur bones. Eagle Sandstone Formation (200-525 feet) Upper layers are sandstone, shale and coal. Massive white to buff sandstone at the base. Bearpaw Shale Formation (800-1,350 feet) Dark gray shale richly studded with marine fossils and hard nodules of mineral matter. Claggett Shale Formation (200-300 feet) Mainly dark gray shale that weathers reddish brown and includes occasional scattered mineral concentrations. Lennep Formation (variable) A fairly thin layer of reddish-brown sandstone composed of fine-grained feldspar. an ancient beach deposit. Pancaked rock layers reveal a rich history Troodon “wounding tooth” First identified: 1856 Length: 6.5-11.5 ft. Weight: 110 lbs. Time period: 75 to 70 million years ago Places found: Montana, Alberta, Wyoming and Alaska Troodon has been credited as the most intelligent dinosaur, though its large brain probably contributed more to its its highly developed senses, fine control of its limbs and fast reflexes rather than to powers of reasoning. With long, grasping forelimbs, sharp teeth and large eyes that gave a degree of stereoscopic vision, Troodon was likely a nimble hunter of small prey. fl Star Tribune graphic by Ray Grumney, Mark Boswell, Jane Friedmann and Dave Silk fl Reporting: Jane Freidmann fl Paleo-Illustrator: Mineo Shiraishi, Dinosaurs of the late cretaceous Sources: Science Museum of Minnesota; American Museum of Natural History; “The Dinosaurs of North America”; “The Illustrated Encyclopedia of Dinosaurs”; The Museum of Natural History in Sendai, Japan; Dinosaur Corporation; zoomdinosaurs.com EARLY MAMMALS Megazostrodon was a primitive mammal about 4 inches long and only a few ounces in weight. It was a furry quadruped with a long tail, body and snout. Its diet may have includ- ed insects. A complete fossilized skeleton was found in South Africa. Jim Freitag/ Star Tribune Jim Freitag/ Star Tribune TRIASSIC PERIOD – LITTLE CRITTERS 248-213 million years ago New organisms evolved including marine invertebrates, mammals and small mammal- like reptiles. Small, primitive, two-footed dinosaurs began to evolve from crocodile-like reptiles. Seed-bearing ferns were replaced by taller evergreen and tropical forests. A mass extinction occurred at the end of this period. CRETACEOUS CARNIVORES INLAND OCEANS As the Earth’s continental plates shifted rapidly in the late Cretaceous period, rifts pushed up the ocean’s floor, forcing sea levels to rise and shallow inland seas to form. At that time one-third of present-day North America was submerged under a north-south sea. The bony, armored ancestors of today’s fish swam the sea until it retreated about 70 million years ago. Dromaeosaurus “running lizard” First identified: 1922 Length: 6 ft. Weight: 33 lbs. Time period: 78 to 68 million years ago Places found: Montana, Alberta Few bones have been found of this sharp-toothed, big-eyed carnivorous cousin to the Velociraptor. It may have used the sharp talons on its forelimbs to keep prey at arm’s length while using the huge claws on its hindlimbs to slash the prey’s belly. The tail may have stiffened to act as a dynamic stabiliser when running at speed and changing direction rapidly. Ornithomimus “bird mimic” First identified: 1890 Length: 8-10 ft. long Weight: 225-375 lbs. Time period: 75 to 65 million years ago Places found: Montana, Alberta, New Jersey, Utah, Colorado, eastern Asia Ornithomimus was a hollow-boned dinosaur that resembled the contemporary ostrich and emu. Its forelimbs were exceptionally long and its mouth formed a flat, hard beak, which indicates the di- nosaur probably consumed small reptiles, insects, fruits and vegetation. Corythosaurus “Corinthian helmet lizard” First identified: 1914 Length: 26-33 ft. Weight: 7,700-8,800 lbs. Time period: 95 to 70 million years ago Places found: Montana, Alberta Corythosaurus was a hadrosaur, meaning it had a long, duck-billed snout. A plant-eater, or herbivore, it had hundreds of teeth suitable for grinding tough plant material. Corythosaurus had a dinner-plate shaped crest on its head with a complex system of breathing tubes running from the nostrils to the throat. It took care of its young and appears to have nested in colonies. It walked on its long hind legs. DINOSAURS OF THE LATE CRETACEOUS Illustrated here are six dinosaurs whose fossilized remains have been found in a layer of exposed rock called the Judith River Formation. Located in the central Montana badlands, this fossil-rich rock layer was formed when rivers carried sediment from the Rocky Mountains across broad flood plains. During the late Cretaceous period, flooding was common. Although there was a cool, dry season, the climate was warm and probably often humid. Lowland forests were dominated by cypress and redwoods, with ferns providing much ground cover. Cattails and water lilies grew in marshes and ponds. Mark Boswell/Star Tribune Source: R.E. Lawlor, “Cretaceous Stratigraphy of Central Montana”