What is "adelphoceras"

Adelphoceras is a middle Devonian coiled nautiloid from Europe with an oval whorl section and shallow depressed zone on the inner, dorsal, rim; a strongly contracted T-shaped aperture; ventral siphuncle containing actinosiphonate deposits, and two rows of spines on either side.

Adelphoceras is included in the nautilid family Rutoceratidae, and is also a part of the Tainocerataceae.