....

"I did not intend the steed of the Witch-King to be what is now called a 'pterodactyl'... But obviously it is pterodactylic and owes much to the new mythology, and its description even provides a sort of way in which it could be a last survivor of older geological eras"

Between this and the description in the book that Varda posted, it sounds like a creature that existed already which was nurtured and twisted by Sauron: the 'modus operendi' of both he and his mentor Morgoth when they needed evil creatures to do their bidding.

Thank you Professor Tolkien!!!!!

"I don't suffer from insanity...I enjoy every minute of it!"