The body of K. soperi consisted of a simple head shield, 16 trunk segments (tergites) and a tail plate. The species reached a length of 234–534 millimetres (9.2–21.0 in) and was in outward appearance almost elliptical, about twice as long as wide, with the widest point in the front third of the body at the 3rd to 5th tergite.[1] The first segment bore a ventral pair of large limbs, known as the antennule, which are about half to two-thirds as long as the body. They consisted of a cylindrical stem and about 15 segments. The segments had a flat outer side and two widely spaced spines.[1]