Braulioceras is a smooth,
orthoconic orthocerid
Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerida that lived from the Early Ordovician () possibly to the Late Triassic (). A fossil found in the Caucasus suggests they may even have survived until ...
with very close spaced
septa (around 8 over a length equal to the diameter of the shell) added to the
Sactorthoceratidae
The Sactorthoceratidae comprise Orthocerataceaen genera with a subcentral suborthochoanitic siphuncle composed of slightly expanded segments and free of organic deposits. The camerae (chambers) of the phragmocone (chambered portion) likewise ...
in 2007. The type species, ''Braulioceras sanjuanense'' comes from the Middle
Ordovician of the
San Juan Formation, Argentine
Precordillera
Precordillera is a Spanish geographical term for hills and mountains lying before a greater range, foothills. The term is derived from ''cordillera'' (mountain range)—literally "pre-mountain range"—and applied usually to the Andes.
Some places ...
.
''Braulioceras'' is very similar to ''
Sactorthoceras
''Sactorthceras'' is an orthoceratoid genus (subclass Nautiloidea s.l.) known from the Middle Ordovician of eastern North America (NY), Norway and Korea and is the type genus of the Sactorthoceratidae.
''Sactorthceras'' was named by Kobayashi i ...
''. The
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 ...
is central, with orthochoanitic 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.
''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''.
References
Paleobiology-db Braulioceras*B. Kröger, et al. 2007. Early orthoceratoid cephalopods from the Argentine Precordillera (Lower-Middle Ordovician). Journal of Paleontology 81(6):1266-128
* Rousseau Flower, 1962. Notes on the Michelinoceratida. Memoir 10, Part II, p. 30. New Mexico Bureau of Mines and Mineral Resources.
Nautiloids
Ordovician Argentina
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