Here's what Tolkien himself said in RotK:
Quote:
The great shadow descended like a falling cloud. And behold! it was a winged creature: if bird, then greater than all other birds, and it was naked, and neither quill nor feather did it bear, and its vast pinions were as webs of hide between horned fingers; and it stank. A creature of an older world maybe it was, whose kind, lingering in forgotten mountains cold beneath the Moon, outstayed their day, and in hideous eyrie bred this last untimely brood, apt to evil.
|
I would interpret the use of the word "eyrie" as an indication that is was an ancient sort of bird. If Tolkien thought of the winged steeds as a counterpart to the Eagles, that would be an additional indication.
__________________
'Mercy!' cried Gandalf. 'If the giving of information is to be the cure of your inquisitiveness, I shall spend all the rest of my days in answering you. What more do you want to know?' 'The whole history of Middle-earth..
.'