Rayonnoceras is a genus of extinct cephalopods that lived around 325 million years ago during the Carboniferous. Although they resemble earlier actinocerids they are now though to belong to the Pseudorthocerida Orientation during life was horizontal. Cameral deposits, more concentrated in the apical part of the shell, are thought to have acted as ballast that compensated for the weight of the animal in the forward part. In life Rayonnoceras was probably a bottom dweller that spent most of its time stationary, waiting in ambush for prey.