The Sactorthoceratidae comprise Orthocerataceaen genera with a subcentral suborthochoanitic

siphuncle The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the li ...

composed of slightly expanded segments and free of organic deposits. The

camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...

e (chambers) of the

phragmocone The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camerae are linked by ...

(chambered portion) likewise have organic deposits that are typically retarded or sparse.

Discussion

The family, Sactorthoceratidae, was established by

Rousseau Flower Rousseau Hayner Flower (1913–1988) was an extremely prolific 20th century paleontologist, known for his eccentric personality. Career Although trained as an entomologist, and a specialist in dragonflies and orthopterans, Flower began study ...

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'', '' Glenisteroceras'', '' 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 in the Treatise (Sweet, 1964); ''Cartersoceras'' and ''Murrayoceras'' in the

Baltoceratidae Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, exist ...

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 The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

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