Orthoceras hunting Murrayoceras in Middle Ordovician ocean.

Both Orthoceras (Darker) and Murrayoceras (lighter) are nautilid cephalopods from Ordovician.

Orthoceras had a conical shell, whereas Murrayoceras's shell was conical but flattened on one side.

The scenario of larger orthocones hunting smaller orthocones on the surface is speculative. However, I chose this scenario for it's unique visual quality of pointy nautilid shells sticking out of the blue ocean.