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