Trocholites is a tarphycerid genus in the fa mily Trocholitidae

Trocholitidae

The Trocholitidae are Tarphycerida with whorls in close contact as with the Tarphyceratidae, but in which the siphuncle, similar in structure, becomes dorsal. The Trocholitidae are derived from the Tarphyceratidae, perhaps from different tarphyceratids....

 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...

 with a gradually expanding, weakly ribbed shell; whorls in contact, dorsum slightly impressed; cross section depressed, venter and sides rounded; 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...

 close to but not at the dorsal margin.

The dorsal siphuncle of Trocholites, and the Trocholitidae is somewhat anomalous and may indicate something about the orientation of the shell during life; placing the last septum high rather than midway or low, typical of most. The prevailing location in most coiled cephalopods is central or ventral, extremely ventral in most ammonoids.

Trochoceras

Trochoceras

Trochoceras is a trochoidally coiled nautiloid cephalopod placed in the nautilid family Rutoceratidae that lived during the Middle and Late Devonian in what is now central Europe....

, of similar name, is a member of the Rutoceratidae

Rutoceratidae

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

 in the Nautilida

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...

, and therefore only very distantly related back through the Bassleroceratidae

Bassleroceratidae

The Bassleroceratidae is a family of gradually expanding, smooth ellesmerocerids with a slight to moderate exogastric curvature, subcircular to strongly compressed cross section, and ventral orthochaonitc siphuncle. The ventral side is typically more sharply rounded than the dorsal side and septa...

.