<human>:  What is the name of the dinosaur that is the most famous fossil found at the Dinosaur National Monument?
<bot>: The most famous fossil found there is the Apatosaurus. It was discovered in 1877 by a man named Othniel Charles Marsh. It is the most complete dinosaur skeleton ever found. It was the first dinosaur to be discovered and described by a paleontologist. It was named after the Greek god Apatosaurus.