Kionoceratidae
Introduction '''Kionoceratidae''' is a family in the Orthocerida, 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.When  Kionoceratidae was first conceived it contained only two genera, ''Kionoceras'' and ''Spyroceras''. ''Spyroceras'' turns out to be a number of genera in different groupings. True ''Spyroceras'' is a Pseudorthoceratid from the Devonian. Middle Silurian 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. Kroger and Isakar (2006) 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.
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