Nothoceratidae is a family of nautiloid cephalopods in the orthoceratoid

Orthoceratoidea

The Orthoceratoidea is a superorder , sometimes considered an infraclass or even a subclass, that comprizes nautiloid orders that have orthoconic to slightly cyrtoconic shells and central to subcentral siphuncles in which there may be internal deposits...

 order 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...

 in which shells are exogastrically or endogastrically breviconic, planospiral, or torticonic; often with a constricted or visored aperture; and a 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...

 commonly composed of concave segments and occupied by actinosiphonate deposits. Some ten genera have been described which lived during the time between the Early 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...

 and Late 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...

. The ancestral form is probably Perimecoceras

Perimecoceras

Perimecoceras is a nothoceratid, nautilitoid order oncocerida, with a slowly expanding, compressed, cyrtoconic shell, known from the Upper Silurian of central Europe....

which is known from the Upper Silurian of central Europe and which is similar in external form the Oonoceras

Oonoceras

Oonoceras is an extinct genus of nautiloid molluscs from the Silurian.-References:* Dinosaurs to Dodos: An Encyclopedia of Extinct Animals by Don Lessem and Jan Sovak...

from the Oncoceratidae

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...

.