Dinosaur Legend (Kyouryuu Densetsu) is a cancelled NES / Famicom game that was in development by HAL Laboratory, a famous developer that gave Nintendo popular series as Kirby and Super Smash Bros. They created many games for the Famicom/NES, but one of them was never release: Dinosaur Legend. It was going to be a curious RPG where you travel with a dinosaur to save the world. It had a game mechanic where the dinosaur steadily evolves (could it have been a Pokemon Ante litteram?).
It is currently unknown why the game was never published but you can see a lonely screenshot below.
Thanks to Susumu for the translation from japanese.