Zittelloceras
Encyclopedia
Zittelloceras is an extinct nauiloid genus from the order Oncocerida
which are among a large group of once diverse and numerous shelled cephalopods, now represented by only a handful of species.
Zittleoceras , which is included in the family Oncoceratidae
, is characterized by subcircular or sightly depressed cyrtoconic shells with ventral, suborthochoanitic empty siphuncles; the shell surface typically with crenulated transverse frills or distinct noncrenulated annulations. Zittleoceras has been found in middle and upper Ordovician sediments in North America and Scotland. (Sweet, 1964)
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...
which are among a large group of once diverse and numerous shelled cephalopods, now represented by only a handful of species.
Zittleoceras , which is included in the family Oncoceratidae
Oncoceratidae
Oncoceratidae, a family in the Oncocerida established by Hyatt, 1884, which is characterized by generally compressed, cyrtoconic and breviconic shells with an exogastric curvature such that the ventral profile is convex or more so than dorsal, and in which the siphucle is generally empty and...
, is characterized by subcircular or sightly depressed cyrtoconic shells with ventral, suborthochoanitic empty siphuncles; the shell surface typically with crenulated transverse frills or distinct noncrenulated annulations. Zittleoceras has been found in middle and upper Ordovician sediments in North America and Scotland. (Sweet, 1964)