Which equid is described as having a slightly stockier, more generalized build better suited for navigating uneven ground?

Answer

The donkey's lineage

The slightly stockier, more generalized build of the donkey's lineage is inferred to be better suited for scrambling over uneven, rocky ground, unlike the more streamlined onager.

Which equid is described as having a slightly stockier, more generalized build better suited for navigating uneven ground?
DonkeyOnager