Winged Beasts, a squandered resource?

[Boromir88]

I wonder, though: do we have any information as to where the so-called fell beasts came from?~Ibrin

I don't think so, or at least nothing new that hasn't already been brought up in the thread.

The difficulty also is exactly what type of creature they were. Tolkien, in some form, compared them to pterodactyls, also I'm pretty sure there is some mention of them having feathers, but there's not much else.

The term "fell beast" is not a specific ID, in the way that a certain race is - like say Elf, Dwarf, Ent...etc. Those words all refer to a specific race, when you see "Dwarf" a specific image pops to mind. "Fell beast" is far more vague, as all it really means is some evil, or deadly, animal or creature and just the descriptive words Tolkien chose to refer to the flying-things the Nazgul rode.