In the War of Wrath, when the Valar, Elves and Men fought against Morgoth and his assembled forces
There Melkor releases his last and greatest force, the fleet of winged dragons, that had never been seen before
To my knowledge, the Fall of Gondolin happened before the War of Wrath, and yet in the Fall of Gondolin, dragons attack the city (apparently with Balrogs riding on them).
Were the dragons at the Fall of Gondolin wingless?