Karoceras is a genus of oncocerid nautiloids that lived during the Silurian and possibly Early Devonian, type genus for the Karoceratidae. The shell is a compressed, exogastric cyrtocone, section sub ovoid. The siphuncle is ventral, near the outer, externally convex curvature. Septal necks flair outwardly, segments are inflated ventrally and are straight dorsally, a character of the family. Karoceras is the only member of the Karoceratidae that is actinosiphonate, a character produced by lamellae projecting radially inward toward the middle of the siphuncle from the connecting rings.