Poterioceratidae
Encyclopedia


The Poterioceratidae is a family of nautiloid cephalopods included in the Oncocerida
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...

 that lived during the period from the Early Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

 to the Early Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 (Mississippian). Members of the Poterioceratidae are distinguished by a subcircular to compressed exogastric shell (curved upwardly so as the lower side, the venter, is convex viewed from the side) that has no hyponomic sinus and a central to subcentral siphuncle
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...

 composed of subquadrate to nummuloidal segments in which the septal necks are more strongly curved on the upper, or dorsal side. This is opposite from the Karoceratidae in which siphuncle segments are inflated ventrally but straight dorsally. Some poterioceratid genera have actinosiphonate structures or annular deposits within the siphuncle. In others it is empty.

The origin of the Poterioceratidae is undetermined but may have their origin in some Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 member of the Acleistoceratidae
Acleistoceratidae
The Acleistoceratidae, named by Flower in Flower & Kümmel 1950, is a family of oncocerids that contains genera characterized by depressed exogastric brevicones and cyrtocones that range from the Middle Silurian to the Middle Devonian...

 or perhaps even in some Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 oncoceratid
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...

through an unknown Silurian genus.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK