The Naedyceras group is made up of three similar and closely related genera, Naedyceras, Gonionaedyceras, and Gyronaedyceras; three gyroconic members of the Brevicoceratidae

Brevicoceratidae

The Brevicoceratidae, named by Flower in 1941, is a family of oncocerids that contains genera characterized by exogastric gyrocones, brevicones, and torticones that tend to develop vestigial actinosiphonate deposits and subtriangular transverse sections...

, within the nautiloid order Oncocerida

Oncocerida

The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian ,in which the connecting rings are thin and siphuncle segments are variably expanded...

.

Naedyceras was named by Hyatt in 1884; Gonionaedyceras, and Gyronaedyceras by Flower in 1945. All three have open, gyroconic coiling, a subtriangular whorl section with a flattened dorsum. The siphuncle in each is ventral with flared out, cyrochoanitic septal necks and inwardly radial, blade-like actinosiphonate developments. All three come from the Middle Devonian of N Am

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, specifically New York, Ohio, and Wisconsin. Differences lie primarily in the symmetry of the whorl section and in the suture.

Naedyceras

Naedyceras is a brevicoceratid described as low-spired, loosely coiled dextral torticones with flattned dorsum and subtriangular whorl section. The body chamber bulges slightly. The aperture in mature specimens is somewhat contracted. Sutures form slight lateral lobes, dorsal lobed, and broad ventral and umbilical saddles. Whorl section is symmetric

Gonionaedyceras

Gonionaedyceras: strongly curved cyrtoconic brevicoceratids with an asymmetric subtriangular transverse section; obliquely flattened inside, dorsal, curvature and narrowed outside, ventral, curvature with a rounded to angular ridge not in the plane of the siphuncle. Sutures have dorsal and lateral lobes and umbilical and ventral saddles. Umbilical saddles are sharper on the left than on the right. Ventral saddles are rounded.

Gyronaedyceras

Gyronaedyceras; Compressed gyroconic brevicoceratids of about 2 volutions with an assymmnetrical, subtraingular whorl section having a broadly rounded to subangular venter and flat dorsum. Sutures are essentially straight and transverse. Actinosphonate structures are discretely developed.

Comparison

Naedyceras, especially, resembles Stereotoceras

Stereotoceras

Stereotoceras is a Middle_ and Upper Devonian genus in the oncocerid family Brevicoceratidae that formed a smooth, depressed, gyroconic shell with the dorsum much flatter that the venter. Sutures are straight ventrally but have dorsal lobes. Growth lines outline a ventral hyponomic sinus but are...

outwardly. Stereotoceras has a depressed, wider than high, cross section and a nummuloidal, beaded, siphuncle. Oxygonioceras

Oxygonioceras

Oxygonioceras is a genus in the Oncocerid family, Brevicoceratidae, from the Middle Silurian of North America and Europe.Oxygonioceras, named by Foeste, 1925, has a loosely coiled, dextrally torticonic shell with a rounded dorsum on the inside of the spiral and an angular or subangular venter on...

is another loosely coiled brevicoceratid but with the dorsum rounded rather than flat.

References

• Sweet W.C. 1964. Nautiloidea -Oncocerida;Treatise on Invertebrate Paleontology
  Treatise on Invertebrate Paleontology
  The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
  
  Part K,Mollusca 3, K277-K317