Maelonoceras is a Late Ordovician - early Silurian oncocerid found in Ontario.
The shell is a faintly gibbous exogastric cyrtocone with subparallel dorsal and ventral profiles but adorally converging sides. The aperture vizored, pear-shaped. The Siphuncle small, ventral.
Maelonoceras is nautiloid cephalopod included in the Oncoceratidae along with such genera as Oncoceras, Belotoceras, Digenuoceras, and Maimoceras.