Superorder Orthoceratoidea Rank Family | Subclass Nautiloidea | |
Similar Aspidoceratidae, Ammonitina, Ancyloceratina, Nautilida, Nautiloid | ||
Spyroceratidae are defined as Pseudorthocerida with uniformly slender siphuncle segments, longer than wide, that contract sharply near either end, in which endosiphuncular deposits first form a compete annulus before fusing ventrally.
References
Spyroceratidae Wikipedia(Text) CC BY-SA