Dinosaurs are a variety of reptiles that are from the Prehistoric Ages. In the real world, they are extinct, but they still exist in the Dr. Slump universe.
Various species of Dinosaurs are seen several times in the background in Penguin Village. Dinosaur were implied to be extinct in "The Mysterious Egg", when Senbei Norimaki mentions that he is going to catch a dinosaur on their trip to the Prehistoric Ages from the Time Slipper. In "Hello, Moon!", Arale Norimaki ends up preventing the extinction of many prehistoric species when she pushes a falling meteorite back into space, resulting in the creation of the Moon and explaining how dinosaurs are non-extinct in the present in Dr. Slump and the Dragon Ball series.