Depending on the family, the siphuncle has orthochoanitic (short and straight) or cyrtochoanitic (outwardly curved) septal necks, which protrude from the septa.

The shell surface may be (depending on the species or genus) smooth, transversely ribbed, or ornamented by a network of fine lirae.

Parsing these relationships out however can become complicated due to similar characteristics through convergent evolution, making certain taxa appear to have a much longer stratigraphic range than in actuality.

Some important characteristics include the diameter and thickness of a calciosiphonate connecting ring and shape of orthocone siphuncles.

The spherical protoconch, or first chamber, of some orthocerids suggests they were ancestors to the Bactritida, small orthoconic forms that gave rise to both the ammonoids and coleoids.

However, the discovery in the Caucasus of a possible orthocerid from the Early Cretaceous suggests that they may have endured much longer as a ghost lineage.