Fellbeasts were giant vicious flying creatures found in J.R.R. Tolkien's fantasy novel, The Lord of the Rings.
The fell beasts were described as large, winged creatures without feathers, similar to dragons that they could almost be mistaken for one. Its pinions were in between horned fingers; and its body gave off a stench. Fellbeasts resembled dragons but were large winged creatures that were bred by the Dark Lord Sauron for war purposes.
For the movie version, fell beasts are depicted as more Wyverns (dragon-like and serpentine creatures that walk on two legs), i.e. their heads appear more like a snake's and they don't have beaks, leading to the common misconception that they are dragons in the books; Tolkien definitely meant a pterosaur-like creature.
The Lord of the Rings