The Sactorthoceratidae comprise
Orthocerataceae
The Orthocerataceae is a superfamily of orthocerid cephalopods that lived from the late Early Ordovician to the Early Cretaceous,Sweet, W. C. 1964. Nautiloidea- Orthocerida; Treatise on Invertebrate Paleontology Part K, Teichert et al (eds) pp K2 ...
n genera with a subcentral
suborthochoanitic 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 ...
composed of slightly expanded segments and free of organic deposits. The
camerae (chambers) of the
phragmocone (chambered portion) likewise have organic deposits that are typically retarded or sparse.
Discussion
The family, Sactorthoceratidae, was established by
Rousseau Flower in 1946, based on the genus ''
Sactorthoceras''. In 1962 Flower pointed out the problem of defining the Sactorthoceratidae based on ''Sactorthoceras''; there being three species groups within the genus: those with (1) short camerae and rather short tubular septal necks, (2) long camerae and slightly expanded siphuncle segments, (3) typically tubular siphuncle segments that are rapidly contracted at the septal foremina. In defining the Sactorthceratidae, the second group with slightly expanded segments was considered. However the type species ''S. goniaseptum'' belongs to the third group, with contracted segments.
Recent classification includes ''
Braulioceras'', ''
Cartersoceras'', ''
Centroonoceras
''Centroonoceras'' is a middle Ordovician cyrtoconic nautiloid cephalopod, otherwise similar to the orthoconic '' Sactorthoceras'' and also included in the Sactorthoceratidae. It was named by Kobayashi, 1934, and has been found in Korea and in ...
'', ''
Glenisteroceras
''Glenesteroceras'', which is of questionable validity, is based on a single specimen from the Lower Ordovician of New York state, described by Rousseau Flower, 1957.
''Glenestoceras'' is described as being a weakly annulate orthocone with a cir ...
'', ''
Leptoplatophrenoceras'', ''
Murrayoceras'', ''
Sactorthoceras'', ''
Scipioceras'', ''
Sigmocycloceras'', ''
Wennanoceras'', and ''
Wolungoceras'', with the Sactorthoceratidae expanded well beyond the composition in the Treatise (1964), consisting then only of ''Sactorthoceras'', ''Centroonoceras'', and ''Sigmocycloceras''.
Among genera now included in the Sactorthoceratidae, ''Glenisteroceras'' and ''Wolungoceras'' were included tentatively in the
Troedssonellidae
Troedssonellidae is a family of orthoceroid cephalopods from the Ordovician, derived from rod-bearing Baltoceratidae, that have a continuous lining within the siphuncle that resembles very thin and slender endocones. Shells are generally slend ...
in the Treatise (Sweet, 1964); ''Cartersoceras'' and ''Murrayoceras'' in the
Baltoceratidae in NMBM&MR Memoir 12 (Flower 1964). Flower (1964) classified ''Wolungoceras'' as an empty siphuncle baltoceratid. ''Cartersoceras'' and ''Murrayoceras'' were given (ibid) as rod-bearing baltoceratids. ''Braulioceras'', ''Leptoplatophrenoceras'', ''Scipioceras'', and ''Wennanoceras'' are more recent additions.
References
*Flower, R.H. 1962. Notes on the Michelinoceratida. Part II Memoir 10, New Mexico Bureau of Mines and Mineral Resources. p. 30.
*Flower, R.H. 1964. The Nautiloid Order Ellesmeroceratida (Cephalopoda) Memoir 12 Ibid. pp 110, 120, 121.
*Sweet, W.C. 1964. Nautiloidea-Orthocerida.
Treatise on Invertebrate Paleontology Part K. Geol Soc. of America and Univ. Kansas Press. p.K233.
Sactorthoceratidae in Paleobio-db
{{Taxonbar, from=Q7397402
Orthocerida
Taxa named by Rousseau H. Flower
Prehistoric cephalopod families