Reedsoceras is a large member of the discosorid

Discosorida

Discosorida is a unique order of cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian. Discosorids are unique in the structure and formation of the siphuncle, the tube that runs through and connects the chambers in cephalopods, which unlike...

 (Nautiloidea) family Westonoceratidae

Westonoceratidae

Westonoceratidae are exogastric, mostly compressed, Discosorida of moderate size from the Middle Ordovician to the Lower Silurian.The siphuncle is typically close to the convexly curved outer margin of the phragmocone -the chambered part of the shell- taken to be ventral but may be more central in...

 from the middle and upper Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 of North America.

Reedsoceras was named as a genus characterized by rapidly expanding exogastric cyrtocones with unconstricted apertures and straight sutures. The siphuncle

Siphuncle

The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula...

 is close to the venter, which is the externally convex side of the shell, and is composed of very short, broadly rounded segments. Structure of the siphuncle wall is unknown.

Reedsoceras seems to be derived from Simardoceras

Simardoceras

Simardoceras is a genus in the discosorid family Westonoceratidae from the Middle Ordovician of Quebec.The shell of Simardoceras is a moderately expanding exogastric cyrtocone, said to resemble a rather large Oncoceras, but with a siphuncle that is definitely discosorid. The venter is almost...

and to be more closely related to a group that also includes Sinclairoceras

Sinclairoceras

Sinclairoceras is a nautiloid cephalopod in the discosorid family Westonoceratidae from the Middle Ordovician Simard Limestone of Quebec. The shell is a compressed exogastric brevicone with venter narrowly and dorsum broadly rounded. The dorsum, at the upper surface, is only slightly concave...

than to othere westonoceratids, especially those with long narrowing body chambers and bent back exogastric phragmocones like Winnipegoceras

Winnipegoceras

Winnipegoceras is an extinct nautiloid genus from the Ordovician belonging to the Order Discosorida.-Phylogeny:Winnipegoceras is included in the discosorid family Westonoceratidae and is derived from Westonoceras...

.