Complete the indicated task to unlock the achievement.

Achievement	How to unlock
Black Hen	Kill 666 Black Hen's.
Black Tipped	Score 90% of the notes and beat Sharkmungus on Hard Rock Difficulty.
Bull Shark	Score 90% of the notes and beat Sharkmungus on Extreme Difficulty.
Compso	Beat Rex on Hard Rock Difficulty.
Devastator	Score 90% of the notes and beat Morton on Violent Difficulty.
Hammerhead	Score 90% of the notes and beat Sharkmungus on Violence Difficulty.
Marlene's Stuff	Find and kill Marlene's shiny.
Nuke Machine	Score 90% of the notes and beat Morton on Extreme Difficulty.
Raptor	Beat Rex on Violence Difficulty.
Rex	Beat Rex on Extreme Difficulty.
Tank	Score 90% of the notes and beat Morton on Metal Difficulty.
Tiger Shark	Score 90% of the notes and beat Sharkmungus on Metal Difficulty.
Triceratops	Beat Rex on Metal Difficulty.
Triforce	Reach end of Chapter 3 on any difficulty.
War Bike	Score 90% of the notes and beat Morton on Hard Rock Difficulty.