What's the smallest dinosaur ever? Well, it's kind of hard to tell, because the fossils that are found aren't always full adults. However, a couple of dinosaurs vie for the position: The smallest well known dinosaur is Microraptor, which is essentially a tiny version of the already small velociraptor we know and love (not anything like Jurassic Park led us to believe). It was about 16 inches long and 2.2 lbs (~1 kg). As small as that is, it doesn't compare to the tiny Epidexipteryx (shown here), which is known only from a single partial fossil and was described in 2008. It is only about 10 inches long and is estimated to weigh 164 g (that's 0.36 lb). Yes, that's about the size of your average hamster, and yes, I want a herd of them as well.
BBC News: New Feathered Dinosaurs Discovered
The Hairy Museum of Natural History: Epidexipteryx hui
Dino-Bird from China Gives Clues to Bird Evolution