In multiplayer, select the wi-fi connection. There, choose the bonus data option to get a dragon message (you will only get the dragon message if you already completed the game). When you get the dragon message, go to the Petrified Woods to fight Duna. Defeat her, then go to hot spring heights to fight Raptin. When you defeat him he will send you to fight Dynal in the pyramid. This is the final dinurian and, when you defeat him, you get the dinurians.
Complete the game to unlock Zongazonga's Castle. Go inside and speak to the staff to pay 3000 G. After that, defeat Zongazonga again to unlock the following: Z-Elasmo, Z-Ptera, Z-Rex, Z-Tricera, and Zongazonga.