Start the game with a saved game file after being online in Monster Hunter to unlock a fourth gallery page.
Blue Rathalos (RioSoul)
Kill a Silver Crown sized Rathalos in trial mode.
Pink Rathian (RioHeart)
Kill a Silver Crown sized Rathian in trial mode.
Trial mode
Successfully complete the "Jungle Menace" quest. The following trials can then be unlocked by completing the indicated quest.
Basarios' Trials: Complete the "Basarios: Unseen Paril" quest.
Cephadrome's Trials: Complete the "The Land Shark" quest.
Gravios' Trials: Complete the "Terror of the Gravios!" quest.
Gypceros' Trials: Complete the "Slay The Gypceros!" quest.
Khezu's Trials: Complete the "The Shadow In The Cave" quest.
Kut Ku's Trials: Complete the "Jungle Menace" quest.
Monoblos' Trials: Complete the "Horn of the Monoblos" quest.
Plesioth's Trials: Complete the "Water Wyvern in the Desert" quest.
Rathalos' Trials: Complete the "Attack Of The Rathalos!" quest.
Rathian's Trials: Complete the either "Queen Of The Desert" or "Slay The Rathian!" quest.