What were the biggest and smallest dinosaurs?

The biggest dinosaurs were, of course, these long neck creatures known technically as the sauropods, the famous apatosaurus, used to use the term brontosaurus but that's no longer an official name in the scientific lineature, although it's a very famous name, thunder lizard it means. As far as the traditional extinct dinosaurs, the smallest animals are close bird relatives, probably in the group troodontidae which were pigeon sized that we found remains of in northeastern China. One thing about small animals is that they preserve much more poorly in the fossil record than large animals do so that our record is highly skewed toward larger sorts of animals as fossils and the small ones just quickly become decomposed or abraded or eaten and things like that, and don't make very good fossils so we know nothing about them.