The Nightmare Longneck is a dragon-like Diplodocus who appears in the episode The Lone Dinosaur Returns in Chomper's nightmare. It is a dream representation of Doc. During the course of the nightmare, it ignores Chomper's pleading not to hurt him and squashes him with its tail in The Mysterious Beyond.
- It appears in the same location that the Spinosaurus lives in The Land Before Time XII: The Great Day of the Flyers and in the TV series. It is one of the desolate areas.