Stereotoceras
Encyclopedia
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 otherwise transverse. The siphuncle in ventral, nummuloidal, with discrete, irregular, actinosiphonate deposits at the septal foramina.
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...
family 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...
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 otherwise transverse. The siphuncle in ventral, nummuloidal, with discrete, irregular, actinosiphonate deposits at the septal foramina.
References
- Sweet. W. C. 1964. Nautiloidea-Oncocerida; Treatise on Invertebrate Paleontology, Part K. Geol Soc of America and Univ Kansas press, R.C. Moore (Ed)