Depicts a herd of sauropod dinosaurs
, Seismosaurus hallorum
(now called Diplodocus
), migrating to new feeding areas during the seasonally dry environment of western North America's late Jurassic Period. Known from a huge, forty-percent-complete skeleton, Seismosaurus was discovered in the Brushy Basin Member of New Mexico's Morrison Formation
. Associated with the skeleton were Gastroliths, or "stomach stones," that may have aided digestion. Credit: "The Long March" © 1994 Mark Hallett
The Morrison formation is a layer of sediments famous for its many dinosaurs. It covers parts of New Mexico, Arizona, Utah, Colorado, Montana, North Dakota and Saskatchewan in Canada. When one visits Dinosaur National Monument, you are looking at dinosaur remains within the Morrison.
It is easily recognized in Utah and Colorado by the "Neopolitan Ice Cream" colours of the layers. Interestingly, dinosaurs are not the most common fossil in it, but rather clams. This is also interesting in that it is well acknowledged by paleontologists that these dinosaurs and clams were buried in a flash flood. However, this flash flood extends for thousands of kilometers, thousands of meters above sea level. Yet, when the demise of the dinosaurs is discussed, an asteroid impact is always brought into play. This simply does not line up with the field evidence.