Octamerella is an extinct prehistoric nautiloidgenus from the oncocerid

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...

 family Hemiphragmoceratidae

Hemiphragmoceratidae

The Hemiphragmoceratidae is a family of endogastrically brevconic oncocerids characterized by elaborately visored apertures in which the hyponomic sinus in mature specimens is on a spout-like process and there may be lateral and dorsal salients. . Shells are compressed with the apical portion...

 that lived in what is now Europe and North America during the Middle 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...

.

Octamerella has a breviconic shell and a mature aperture that is contracted so as to have four pairs of dorsolateral sinusus, four on each side, and a narrow mid dorsal salient. The two ventral-most sinus pairs are typically the larges while the dorsal-most pair is short and wide, forming a circular opening. (Sweet, 1964)

See also

• Nautiloid
  Nautiloid
  Nautiloids are a large and diverse group of marine cephalopods belonging to the subclass Nautiloidea that began in the Late Cambrian and are represented today by the living Nautilus. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, and...
  
  
  • List of nautiloids