Currently unavailable in the beta without using bugs, this mutation is referred to as "Quick Sprint" on the official website. You can get it by eating a Tetracrab. This mutation is quite useful when you don't have stamina and need to run from the Cylinder.
"These legs allow a Trebhum to accelerate rapidly and to run more quickly in general."
This mutation can be permanently activated by mixing 4 Tetracrabs, 4 Rucklefruits, and 4 Refined Minerals.