What kind of D&D animals can you use?

I am a beginner in the Dungeons and Dragons world and have moved up with my group to when we want to use mounts now, I am a Dwarf Barbarian and want to use a dire boar as a mount, Am i able to do that or am i gonna have to use something else? If so can you please list them. I like riding the dangerous animals that can really help hurt the enemy, and have special traits.