Nobita and a companion go to a dinosaur display. During a fossil excavation adventure there, he promises his pals that he will find a dinosaur and that if he does not, he will eat monkey nuts with his eyes. As he leaves the excavation experience he trips over a rock and suspects that he has found the fossil of an egg. He returns home and persuades Doraemon to put the "time wrapping cloth" on the fossil egg, resulting in the appearance of twin feathered dinosaurs. Doraemon discovered that they are a new dinosaur species not included in the "Complete Encyclopaedia of Space." Nobita names the twin dinosaurs Kyu and Myu and learns how to care for them with the help of Dr. Dinosaur. The two rapidly expanding creatures gradually show differences in their development.