Xenoscapha rotatiolateralis is a late-surviving Late Cambrian vetulicolid, about 10cm long (~4″), that spends daylight hours resting on its side on the seafloor much like present-day flatfish — and this has resulted in a similarly asymmetrical “rotated” body plan. The right side of its body is flattened and now acts as its underside, while its left side is cryptically-colored and functions as the upper surface.
During the night it swims upwards to filter-feed on plankton, propelled by its paddle-like tail. Scattered spots in the left “upper” cuticle are light-sensitive, forming a simple distributed visual system similar to the aesthetes of chitons.