Trochoceras is a trochoidally coiled nautiloid cephalopod placed in the nautilid

Nautilida

The Nautilida constitute a large and diverse order of generally coiled nautiloid cephalopods that began in the mid Paleozoic and continues to the present with a single family, the Nautilidae which includes two genera, Nautilus and Allonautilus, with six species...

 family Rutoceratidae

Rutoceratidae

The Rutoceratidae are the prototypical nautilids, derived probably from either the Brevicoceratidae or Acleistoceratidae of the Oncocerida early in the Devonian...

 that lived during the Middle and Late Devonian

Devonian

The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

 in what is now central Europe.

The Trochoceras shell is a narrow, smooth, offset gyrocone consisting of little more than a single whorl, trochoidally grown in the sense of left hand screw. The phragmocone, with chambers, is ovate in cross section; the body or living chamber, quadrangular, with two pairs of winglike processes, one at the aperture and one at its base. The siphuncle is ventral, segments fusiform.

Trochoceras resembles the rutoceratid Ptenoceras except the latter has a planar gyroconic shell with narrow projections extending laterally from the body chamber.

References

• Bernhard Kummel, 1964. Nautiloidea -Nautilida. Treatise on Invertebrate Paleontology, Part K. Geological Soc. of America and Univ of Kansas press.