Tasmanian Devil

Tasmanian Devils are one of the few species on Mobius that never fully evolved after the Xorda Attack on Earth. Their keen sense of smell makes them good for tracking scents, so they were used to help find the prisoner Sonic the Hedgehog after he escaped from a crashed plane headed for the Devil's Gulag. (StH: #48)

But Thrash seems to be fully evolved, but Doctor Finitevus refers to him as a failed experiment.