Nobita and Doraemon were finding out the truth about a real dinosaur. Nobita saw something under the ocean when they come across a cave that leads to an underground world full of dino-people. Nobita and his friends are amazed
Doraemon: Nobita's Dorabian Nights
Doraemon: Nobita and the Windmasters
Doraemon: Nobita and the Birth of Japan
Doraemon: The Record of Nobita, Spaceblazer