Short answers, pulled from the story.
Apatosaurus means "deceptive lizard," from the Greek words for deception and lizard. Othniel Charles Marsh chose the name in November 1877 because its chevron bones resembled those of mosasaurs rather than other dinosaurs.
Apatosaurus lived in North America during the Late Jurassic period, about 152 to 151 million years ago. Its fossils come from the Morrison Formation in Colorado, Oklahoma, New Mexico, Wyoming, and Utah.
Apatosaurus had an average length of 21 to 23 meters and an average mass of 16.4 to 22.4 tons. A few specimens suggest a maximum length up to 30 percent greater than average and a mass of about 33 tons.
Brontosaurus was long treated as a junior synonym of Apatosaurus after Elmer Riggs reclassified its type species as Apatosaurus excelsus in 1903. A 2015 study by Tschopp, Mateus, and Benson concluded Brontosaurus is a valid distinct genus, though not all paleontologists agree.
The skull of Apatosaurus was confused with those of Camarasaurus and Brachiosaurus until 1909, when an A. louisae skeleton was found with a Diplodocus-like skull nearby. The first true Apatosaurus skull was not mounted on a skeleton until the 20th of October 1979, at the Carnegie.
Apatosaurus likely had an avian respiratory system with parabronchi, multiple pulmonary air sacs, and a flow-through lung. An avian lung would need about 600 liters, while a mammalian system would require 2,950 liters, more space than its estimated 1,700-liter thoracic volume could hold.