Kionoceratidae is a family in the

Orthocerida 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 ...

, proposed by Hyatt in 1900 for genera characterized by prominent ornamentation in the form of longitudinal ribs, ridges, or lirae, or combinations thereof, sometimes with similar transverse ornament or faint transverse annulations.Sweet 1964: Nautilodea - Orthocerida; Treatise on Invertebrate Paleontology, Part K, Mollusca 3; Teichert and Moore (eds). Univ. Kans. Press. When Kionoceratidae was first conceived it contained only two genera, '' Kionoceras'' and ''

Spyroceras ''Spyroceras'' is a genus of pseudorthocerids from the Devonian of North America and Europe, defined by Hyatt in 1884. Pseudorthocerids are a kind of orthocertaoid, a taxonomic group within the Nautiloidea. Specifically ''Spyroceras'' belongs t ...

''. ''Spyroceras'' turns out to be a number of genera in different groupings.Flower 1962 Notes on the Michelinoceratida, Part II Memoir 10, State Bureau of Mines and Mineral Resources, Socorro New Mexico True ''Spyroceras'' is a Pseudorthoceratid from the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

. Middle

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

genera related to ''Kionoceras'' studied by Barrande show a general internal similarity. Anterior siphuncle segments tend to become fusiform, some being constricted at the septal openings. Cameral deposits are confined apically and, where observed, siphonal deposits are simple annuli. While there seems to be a true relationship among the Silurian genera with similar external markings, the scope of ''Kionoceras'' itself is uncertain creating some doubt as to the establishment of a family based on such an uncertain genus. Flower sought to include Kionceras along with related genera in what he called the "already overcrowded Michelinoceratidae". Sweet (1964) in the Treatise presented kionoceratids as a subfamily, the Kionoceratinae, in the orthocerid family

Michelinoceratidae Orthoceratidae is an extinct family of actively mobile carnivorous cephalopods, subclass Nautiloidea, that lived in what would be North America, Europe, Asia, Africa, and Australia from the Ordovician through Triassic from 490—203.7 mya, exis ...

. Kroger and Isakar (2006)Kröger, Bjorn, & Isakar, Mare. (2006) Revision of annulated orthoceridan cephalopods of the Baltoscandic Ordovician. Fossil Record 9(1):137-163. cast some doubt as to the validity of this subgroup. which depends on whether it consists of convergent genera with different ancestries (polyphyletic) or is a true monophyletic group with a single ancestry. Regardless it is still a useful, descriptive, grouping within the Orthocerida.

References

{{Taxonbar, from=Q6414518 Nautiloids