Microraptor

Microraptor is a transitional form. It represents, along with other dromaeosaurids (a.k.a. "raptors"), a branch of evolution path from dinosaurs to birds. The 24 centimeter creature had feathers and was able to glide between trees, yet it also has a tail that is "clearly dinosaurian". Bizarrely, Microraptor has four wings, i.e. feathered legs, as opposed to birds' two.

The latest discovered genus related to Microraptor, Changyuraptor, has a feathered tail 30 cm long, consistent with gliding flight.