Final answer:
The Upper Jurassic Morrison formation is known as the "graveyard of dinosaurs" due to the abundance of dinosaur fossils found in this formation.
Step-by-step explanation:
The Upper Jurassic Morrison formation is aptly known as the "graveyard of dinosaurs". This formation, which dates back to the Jurassic Period, contains abundant dinosaur fossils and has provided valuable insights into the diversity and evolution of dinosaurs during this time. The dominance of dinosaurs lasted until the end of the Cretaceous period, when a mass extinction event led to their extinction.