The Brontosaurus (now called Apatosaurus) was discovered in 1879 by Othniel Charles Marsh, a professor of paleontology at Yale University. This dinosaur was from the diplodocidae family and lived for millions of years during the late Jurassic period. Brontosaurus was at the time the largest dinosaur discovered at the time and still is the largest one (in mass) discovered to date. There has been some controversy over the name brontosaurus because when it was discovered, it was believed to be a different species than the Apatosaurus, discovered two years earlier. In 1903 scientists realized that both dinosaurs where the same so they reverted back to the less charismatic name Apatosaurus. However the name Brontosaurus which is now just considered a synonym was still widely used in popular literature until the mid 1970's. In fact, in 1989 the US postal service used a brontosaurus on one of their stamps with the name "brontosaurus" printed on it simply because it is more familiar to the general public then its scientific name. If you actually translate the name Brontosaurus, it means Thundering Lizard and is a member of the Sauropoda dinosaurs. Because they were herbivores the needed really long necks like a modern day giraffe so they could eat the leaves off of really tall trees although as many professionals clearly state that these dinosaurs' could not be raised high enough to eat from trees.
Just for fun we have a soundclip available for you to hear what a Apatosaurus could've sounded like. Click to the Dinosaur Sounds area to hear it. Please note that the dinosaur sounds are only for entertainment and are not an actual fact.