Trochoceras

Trochoceras
Trochoceras regale, from Lochkov, Czech Republic, at National Museum (Prague)
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Nautilida
Family:
Genus:	Trochoceras Barrande, 1848

Trochoceras is a genus of trochoidally coiled nautiloid cephalopods placed in the nautilid family that lived during the Middle and Late Devonian 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.

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Wikipedia