To access one secret character, you must beat Arcade mode with two different dinosaurs. IN other words, you'll get a seccret character every other time you win. There are a total of 6 extra dinosaurs.
Survival and Choice Modes:
Beat Arcade mode with any character to enable these in the Main Menu.
Beat Arcade mode with every character (including the secret ones).
Beat every dinosaur in Survival Mode without dying. Invulnerability can be found in the Options menu.
Beat Survival Mode to unlock a new skin for that dinosaur. Press Triangle to select the new skin when choosing a character.
Enable All Extras And Dinos 80030f460101 80030f4e0101 80030edc0101 80030ede0101 80030ee00101 80030ee20101 Infinite Timer 8007714c003c P1 Quick Win 80060f3c0003 80060f3e1480 80060f4a2400 P2 Quick Win 80060f3c0003 80060f3e1080 80060f4a2400 Start on Final Stage 80030ec60008 P1 Never Wins 30030eb70000 P2 Never Wins 30030eb80000
Thanks to Revolution readers UPSBob and Martin Brodeur!