Primal ultralisks drastically different from their Zerg Swarm counterparts, being significantly smaller, possessing lower health, and lacking the large shield-like carapace above a normal ultralisk's head. They also attack differently, as their kaiser blades, instead of being mounted to their backs, are attached to their front legs in the form of large, retractable claws. They also look more similar to ravasaurs, Brakk and tyrannozor.
Many zerg ground units may burrow, become invisible and may be revealed primarily by detectors, and may not move or attack. Exceptions are the roach, which may move while burrowed, the infestor, which may move and cast Infested Terran, and the baneling, which can detonate while burrowed.
Some units can unburrow via autocast, causing them to emerge and attack when an enemy moves into range.
The primal ultralisk originally had a "Devour" ability, where it swallowed a non-massive enemy unit. The enemy unit would not be destroyed, but would be removed from battle and take damage over time as long as it remained swallowed. Destroying the primal ultralisk frees the swallowed unit.