Smallest Dinosaurs-Microraptor

Name: Microraptor (Greek for "small thief"); pronounced MY-crow-rap-tore
Habitat: Woodlands of Asia
Historical Period: Early Cretaceous (130-125 million years ago)
Size and Weight: About 2 feet long and 3-4 pounds
Diet: Probably insects
Distinguishing Characteristics: Tiny size; primitive feathers; wings on arms and legs
About Microraptor: Probably because it was so small, Microraptor fossilized unusually well--paleontologists in China have unearthed about two dozen more-or-less complete specimens of this tiny, feathered raptor of the early Cretaceous period, complete with traces of internal organs and primitive feathers.
The most spectacular fact about Microraptor is that it had not one, but two, sets of primitive wings--one on its forearms (similar to other birdlike dinosaurs, like Archaeopteryx), and one on its hind legs. This formidable feathered arsenal notwithstanding, scientists believe Microraptor was, at best, an occasional glider, much like a flying squirrel--and probably spent most of its life high up in the branches of trees. (A recent study has shown that the feathers of Microraptor were black and glossy, and likely evolved more as a way to attract mates than to fly the short distances between trees.)
This leads to the important question: was Microraptor a crucial "missing link" in the gradual evolution of dinosaurs into birds, or did it represent a four-winged experiment that (literally) never quite got off the ground? The answer may await future fossil discoveries, but the lack of any four-winged birds living today should give you an important clue.