Short answers, pulled from the story.
Othniel Charles Marsh named the creature Apatosaurus in 1877 after discovering fossils in Morrison, Colorado. The initial discovery was made by Arthur Lakes, a local miner who sent specimens to Marsh and his rival Edward Drinker Cope.
A complete skull designated CM11162 was found in 1909 at Dinosaur National Monument by Earl Douglass. This discovery occurred during the first expedition to what would become the Carnegie Quarry and corrected over a century of scientific error regarding the animal's head shape.
Elmer Riggs declared Brontosaurus invalid in 1903 because the species was too similar to Apatosaurus ajax to warrant a separate genus. A 2015 study by Emanuel Tschopp, Octávio Mateus, and Roger Benson proposed that Brontosaurus excelsus was distinct enough to warrant its own genus again.
Apatosaurus reached near-adult sizes in about 10 years and lived for approximately 20 to 30 years. Some specimens reached sexual maturity by 19 to 21 years of age before dying in their late 20s or early 30s.
The tail made up over 50% of the total body length and recent research suggests it functioned as a sensory organ rather than a weapon. Baron proposed in 2020 that the tail allowed the animal to keep in touch with individuals behind and on the sides while migrating.
Apatosaurus lived approximately 152 to 151 million years ago in the western United States within the Morrison Formation. This semiarid environment featured distinct wet and dry seasons and supported a diverse array of dinosaurs including Allosaurus and Stegosaurus.