Anyway, our particular specimen is Seismasaurus hallorum, the former of which means "Tremor Lizard." Scientists are still undecided on whether or not this is the most epic title in the history of the Animalia regnum, but many continue to argue in its favor to this day. Seismasaurus was discovered by in 1991 resting in New Mexico's Morrison Formation by Gillette, who I am assuming is a guy and not a razor company. This creature lived in the tail end of the Jurassic period, and is estimated to be up to 33 m long and 33 tons (that's about 108'3" for you non-metric folk). For comparison, a bull african bush elephant is 24 ft. long and weighs at most 11 tons (according to the Nature Conservancy). Never fear, it ate plants.
Now bear with me now, since technicalities are starting

to come in. As I already
stated, Seismasaurus is a "long-neck" or sauropod.
For those of
you with taxonomical proficiencies (like me!), Sauropodomorpha is a sub-order under the Saurischia Order. Most
(if not all) dinosaurs fall into one of two Orders: Saurischia or Ornithia, the difference between the two groups lying in the structure of their hips. As you can see, I have included diagrams of the two types of hips within my boring wall of text, with Saurischian on the left and Ornithischian on the right (thank you, http://museumvictoria.com.au). As a general rule, meat-eaters are Saurischian and plant-eaters are Ornithischian.
Now to screw with you. Sauropods are Saurischian. Yes, even science has exceptions to the rules. If you've kept up with us so far, you know know that a "long-neck" is actually a dinosaur which is a member of the Saurischian Order and the sauropod (the shorter form of sauropodomorpha) sub-order. But it doesn't end there! There are different types of sauropods, each with their own unique traits, and ridiculously long necks. After all, this is how cladistics works. To spare you unending suffering, however, I'll stop here, and maybe post something on different Sauropods if enough people scream for it in the comments. (and I know that's going to happen).
***On a side note, all of the information regarding specifics on a species discovery, size, mating habits, and whatnot is taken from the Dinobase at the University of Bristol. <http://dinobase.gly.bris.ac.uk/>