Kionoceratidae
Encyclopedia
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.
Orthocerida
Orthocerida is an order of extinct nautiloid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic . A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous...
, 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
Kionoceras
Kionoceras is an extinct nautiloid cephalopod genus included in the orthocerid family Kionoceratidae with scattered worldwide distribution from the Middle Ordovician to the Lower Permian. Kionoceratids are orthocerids with prominent longitudinal ornamentation on their shells, sometimes augmented by...
and Spyroceras
Spyroceras
Spyroceras is pseudorthocerid genus 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...
. Spyroceras turns out to be a number of genera in different groupings. True Spyroceras is a Pseudorthoceratid
Pseudorthoceratidae
Pseudorthoceratidae is an extinct family of actively mobile aquatic carnivorous cephalapods belonging to the subclass Orthoceratoidea endemic to what would be North America, Asia, and Europe during the Silurian living from 460.5—251 Ma, existing for approximately .In life, these animals may have...
from the 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...
. 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...
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.