Clitendoceras
Encyclopedia
Clitendoceras is a member of the Endocerida from the Lower Ordovician (m-u Canad ) with an elongate shell with a slight downward, endogastric, curvature and a siphuncle
that lay along the ventral margin. Common for endocerids, the chambers are short and the septa close spaced with sutures sloping forward across the back of the shell. Septal necks are short in the young, lengthening in the adult. Endocones are simple, but with the ventral side of the last formed projecting forward. The endosiphotube running down the middle is arched on top and somewhat flat on the lower side.
Clitendoceras appears early in the Domingian stage of the Lower Ordovician ( Canadian ), probably derived from Proendoceras, and is the likely ancestor of the mostly compressed and breviconic pilocerids as well as of more similar forms such as Mcqueenoceras.
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...
that lay along the ventral margin. Common for endocerids, the chambers are short and the septa close spaced with sutures sloping forward across the back of the shell. Septal necks are short in the young, lengthening in the adult. Endocones are simple, but with the ventral side of the last formed projecting forward. The endosiphotube running down the middle is arched on top and somewhat flat on the lower side.
Clitendoceras appears early in the Domingian stage of the Lower Ordovician ( Canadian ), probably derived from Proendoceras, and is the likely ancestor of the mostly compressed and breviconic pilocerids as well as of more similar forms such as Mcqueenoceras.