The cervical vertebrae and the bones in the legs of Apatosaurus were bigger and heavier than that of Diplodocus although, like Diplodocus, Apatosaurus also had both a long neck and a long tail.
The name Brontosaurus has also been used for Apatosaurus, both scientifically and popularly, and at one point which name should be used was a source of controversy.
Fossils of Apatosaurus species have been found in the United States at Nine Mile Quarry and Bone Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma, and Utah.
The name Apatosaurus means "deceptive lizard," so-named because the chevron bones (the bones on underside of tail) were like those of Mosasaurus, a large, carnivorous sea-dwelling reptile.
In 1877, O. C. Marsh first published notes on his discovery of Apatosaurus ajax, naming and describing it in two paragraphs without illustration.
To aid in processing food, Apatosaurus may have swallowed gizzard stones (gastroliths) in the same way that many birds do today, as its jaws lacked molars with which to chew tough plant fibers.
The overall thoracic volume of Apatosaurus has been estimated at 1,700 liters allowing for a 500-liter, four-chambered heart (like birds, not three-chambered like reptiles) and a 900-liter lung capacity.
The name Apatosaurus, having been published first, was deemed to have priority as the official name.
Assuming Apatosaurus had an avian respiratory system and a reptilian resting-metabolism (it certainly could not fly), it would need to consume only about 262 liters (69 gallons) of water per day.
In 1903, it was surmised by Elmer Riggs of the Field Museum in Chicago that Brontosaurus excelsus was in fact an adult Apatosaurus.
Robert T. Bakker made Apatosaurus yahnahpin the type species of a new genus, Eobrontosaurus in 1998, so it is now properly Eobrontosaurus yahnahpin.
Like most sauropods (a suborder or infraorder of dinosaurs), Apatosaurus had only a single large claw on each forelimb.
Marsh had found no skull associated with either Apatosaurus or Brontosaurus, so he mounted the skeletons with the head of this other sauropod genus (Gould 1991).
Apatosaurus (Greek ???????? or ?????????, meaning "deceptive" and ?????? meaning "lizard"), also known as Brontosaurus, is a genus of sauropod dinosaurs that lived about 140 million years ago during the Jurassic period.
Apatosaurus is believed to have browsed the tops of trees, on riverbanks.