Where is Chocobo's Dungeon 1 for PSX? Why the sudden jump to 2?
The Predecessor to Chocobo's Dungeon 2 is called Chocobo's Mysterious Dungeon (Chocobo no Fushigina Dungeon) for the PSX.
You might read about it in the link above. It was primarily released for Japan and probably did not get a translation till much later.