I saw an announcement about the discovery of "miniature" dinosaurs in the Post on Wednesday, but didn't really understand the significance until I read this article about the same topic:
When unusually small dinosaur fossils were found in a quarry on the northern edge of the Harz Mountains in 1998, it was initially assumed that these were the remains of a group of young dinosaurs. This was a fallacy, as the Bonn palaeontologist, Dr. Martin Sander, recently discovered.
"Unusually small" in this case still means something as big as most cars, but when you're talking dinosaurs, that's definitely on the tiny side.
Interesting fact: According to Predatory Dinosaurs of the World, there are no dinosaurs (at least that we've found) smaller than a chicken. It seems mammals took over all the small land-based niches, and dinos took everything else.