| Braulioceras Temporal range: Middle Ordovician | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | † Orthocerida |
| Family: | † Sactorthoceratidae |
| Genus: | †Braulioceras Kröger et al, 2007 |
Braulioceras is a smooth, orthoconic orthocerid with very close spaced septa (around 8 over a length equal to the diameter of the shell) added to the Sactorthoceratidae in 2007. The type species, Braulioceras sanjuanense comes from the Middle Ordovician of the San Juan Formation, Argentine Precordillera.
An orthocone is an unusually long straight shell of a nautiloid cephalopod. During the 18th and 19th centuries, all shells of this type were named Orthoceras, creating a wastebasket taxon, but it is now known that many groups of nautiloids developed or retained this type of shell.
Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic. A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous. They were most common however from the Ordovician to the Devonian.
In biology, a septum is a wall, dividing a cavity or structure into smaller ones.
Braulioceras is very similar to Sactorthoceras . The siphuncle is central, with orthochaonitic septal necks and segments which are slightly expanded between septa, giving it a beaded appearance. The thickness of the connecting rings is similar to that in ellesmerocerids. Endosiphuncular or cameral deposits are unknown.
Sactorthceras is an orthoceratoid genus known from the Middle Ordovician of eastern North America (NY), Norway and Korea and is the type genus of the Sactorthoceratidae.
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. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through small openings in the walls dividing the chambers.
The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.
Braulioceras is distinguished from Sactorthoceras by its more closely central siphuncle, and expanded segments without the contractions at the ends as in the type species of Sactorthoceras, S. gonioseptatum.
