Archaeopteryx is the oldest known bird. While the Microraptor is considered a dinosaur with feathers like a bird, Archaeopteryx is already a bird. The first bird ... Jurassic.
They are very similar, are common features of other theropods: bone thing, sharp claws, beak with small but sharp teeth and feathers, both forelimbs and hind.
But unlike Microraptor, Archaeopteryx flew better, not only was involved in planning from branch to branch. Perhaps its flight is not elegant as the an albatross or as fast as a swift, but was the first to fly. and that is a lot. Possibly its fly mode would seem very strange if we saw now. Archaeopteryx also had long feathers on the hind legs, along with feathers front, it flew in a strange mode. Some think that because of this, was more agile in flight modern birds, but their ability to fly long distances would be less.
Not very big, measuring just 35 cm, and weighed just under 500 gr. Its brain was proportionally greater than other theropods and structure of his ear and was similar to that of modern birds.
We could say that its size was similar to that of a magpie .... Consider the differences:
Incidentally, the Velociraptor, is a close relative.