Vilka fåglar var Nazgul flög på?

Jag tror inte att de någonsin fått ett namn. Årtalet i bilaga B hänvisar bara till "Winged Nazgûl". Den enda gången vi ser en närbild är i Bok V, kapitel 6: Slaget vid Pelennor-fälten:

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. And the Dark Lord took it, and nursed it with fell meats, until it grew beyond the measure of all other things that fly; and he gave it to his servant to be his steed.

Ett citat från RotK, Kapitel Slaget vid Pelennor-fälten :

The great shadow descended like a falling cloud. An 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. And the Dark Lord took it, and nursed it with fell meats, until it grew beyond the measure of all other things that fly; and he gave it to his servant to be his steed. Down, down it came, and then, folding its fingered webs, it gave a croaking cry, and settled upon the body of Snowmane, Digging in its claws, stooping its long naked neck.

Det verkar som uttrycket "En varelse av en äldre värld, kanske det var", tycks indikera att det är antingen en bokstavlig dinosaur eller ett djur från första ålder, långt bortglömt. Men om de hade levt även under första ålder, skulle någon säkert ha komma ihåg det. Tolkien utvecklar aldrig mer.

Min slutsats: förmodligen en dinosaurliknande varelse, bevarad i en grotta någonstans, som Sauron hittade och vriden. Vi får inte veta vad det kallas exakt, vilket är var det hela generiska "fölldjuret" kom ifrån.