Sega released a new video for Super Monkey Ball 3D. While the game looks like any other banana grabbing game in the series, the stages shown in this trailer have rails.
Much like Marble Madness before it, the challenge of Super Monkey Ball games is carefully tilting the world with an analog stick (in this case the "slide pad") or banana shaped joystick. Make a mistake and AiAi falls off the edge or in this game bumps into a lifesaving rail.
These are probably levels from the beginning of the game, but it’s an interesting design change considering that none of the stages in the very first Super Monkey Ball game had bumpers.