Iguana parrot

History
The Reptile Bird resembles a cross between a green parrot and a lizard. This creature has feathers and is capable of flight, but has many reptilian characteristics as well. It has a parrot-like beak and a feathered tail, but its wings end in claws and it moves on all four limbs when it chooses not to fly. Its feet also seem to lack the reversed toe characteristic of all modern birds, giving it a more reptilian appearance. The green parrot also has a small dorsal fin on its back. A favorite pet of sailors and pirates. This flying reptile is temperamental and loyal only to the person on whose shoulder it perches.

A Reptile Bird appears in "The Waterbending Scroll."

Connection
It has long been thought that birds evolved from dinosaurs, and possible links between the two have been studied intensely. The earliest known bird, archaeopteryx, shares many characteristics with the green parrot Reptile Bird in Avatar. (avatarspirit.net)