Dragons occur often in Percy Jackson and the Olympians and The Heroes of Olympus trilogy. Several were sighted in the Lincoln Tunnel in The Last Olympian, and according to Grover, a baby dragon came in Harlem and murdered a dozen nature spirits. However, they are currently extinct thanks to Zeus. Also, in The Lightning Thief, Percy uses dragon blood to create an antidote for his mother, who has been poisoned by the Fury Calliope. This episode takes place about two years before The Titan's Curse, so Draconia are still alive and well. In conclusion, there are still dragons in Percy Jackson! Or at least, there was up until about two years ago when they were killed by Zeus.