P. whittingtoni had a pair of massive anterior limbs that corresponded to the feeding limbs of other anomalocarids. The anterior limbs had a row of flexible, hair-like spines that corresponded with each segment of each limb. Unlike K. kierkegaardi, P. whittingtoni's mouth was relatively large, though it does not appear to have any large biting surfaces like the mouth of Anomalocaris. It had 11 pairs of lateral lobes, and 11 pairs of relatively large, lobopod-like legs. None of the fossil specimens have any suggestion of posterior cerci, or tail-flaps.
The massive anterior limbs, with their comb-like rows of spines, suggest that P. whittingtoni was a planktivore.