Also sometimes referred to as Aetos Kaukasos (or Caucasus Eagle, after the mountain range it inhabited) or Aetos Dios (Just Zues's Eagle). The latter is probably not the same eagle since it seems the legend doesn't seem to link to the myth of Prometheus in any way other than it being another of Zeus's eagles, which he had an apparent affinity for.
It's just a theory, but judging by the wing like protrusions and the fact that
something has to play the part of the eagle I would say that this is a highly likely candidate to be our new xenomorph.
The piece is titled 'Alien Monster IV' and can be found on page 7 of Giger's Alien. If it's so, I'm satisfied. It seems a natural evolution of the slithering creature spotted in the new trailers.
I suggest checking out this excellent blog entry on
Alien Explorations where the author 'wmmvrrvrrmm' points out some intriguing details about the piece. If you've been following the Prometheus speculation you may notice some similarities to recently uncovered details and rumors.