Plectronoceras is the earliest known shelled cephalopod, dating to the Late Cambrian.[1][2][3] None of the fossils are complete, and none show the apex or aperture of the shell.[3] Approximately half of its shell was filled with septa; 7 were recorded in a 2 centimetres (0.79 in) shell.[4] Its shell contains transverse septa separated by about half a millimetre, with a siphuncle on its concave side.[3] Its morphology matches closely to that hypothesised for the last common ancestor of all cephalopods.[3]
Plectronoceras is the type genus of the family Plectronoceratidae. Fossils of Plectronoceras have been found in the San Saba Limestone of Texas.[2]
Plectronoceras has been suggested to play 4 roles. Click below to see other actors suggested for each role, and vote for who you think would play the role best.
