Here is the full list of all 23 Gigantosaurus: Dino Kart achievements.
Win all the adventure races in third position or better
Unlock all characters
Unlock all tracks
Complete the Mount Oblivion Cup in Adventure
Fly for 5 minutes totally
Accumulate 10 minutes of total drift
Win 10 Races
Complete the Jungle Cup in Adventure
Complete the Savannah Cup in Adventure
Come across Giganto
Win The first race in adventure
Finish The Tutorial
Drift for 30 seconds in a race
Drift for 5 seconds in a row
Step on a boost pad 30 time
Use all skills
Find a shortcut
Win the first race in single player
Win a race in split-screen
Use a Skill for the first time
Unlock all vehicle’s skins
Win a 4 player split-screen race
Win all the adventure races in first position