Sactorthoceratidae
Encyclopedia
The Sactorthoceratidae comprise Orthocerataceaen genera with a subcentral suborthochoanitic siphuncle composed of slightly expanded segments and free of organic depsits. The camerae (chambers) of the phragmocone (chambered portion) likewise have organic deposits that are typically retarded or sparse.
. Later Flower (1962) pointed out the problem of defining the Sactorthoceratidae based on Sactorthoceras with 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 segements 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 Sactorthoceratade 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
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.
Discussion
The family, Sactorthoceratidae, was established by Rousseau Flower in 1946, based on the genus SactorthocerasSactorthoceras
Sactorthceras is an orthoceratoid genus known from the Middle Ordovician of eastern North America , Norway and Korea and is the type genus of the Sactorthoceratidae....
. Later Flower (1962) pointed out the problem of defining the Sactorthoceratidae based on Sactorthoceras with 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 segements 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
Braulioceras
Braulioceras is a smooth, orthoconic orthocerid with very close spaced septa added to the Sactorthoceratidae in 2007...
, Cartersoceras
Cartersoceras
Cartersoceras is a nautiloid cephalopod genus placed in the Orthocerid family Baltoceratidae, established by Rousseau Flower, 1964, for species formally included in part in Murrayoceras, and in part in "Sacotoceras", which are typical of Murrayoceras in all features except that the siphuncle...
, Centroonoceras
Centroonoceras
Centroonoceras is a middle Ordovician cyrtoconic nautiloid cephalopod, otherwise similar to the orthoconic Sactorthoceras and also included in the Sactorthoceratidae...
, Glenisteroceras, Leptoplatophrenoceras, Murrayoceras
Murrayoceras
Murrayoceras is a nautilid cephalopod included in the orthocerid family Baltoceratidae, wide spread in the Middle Ordovician of North America, characterized by a depressed orthoconic shell with a subtriangular cross section and flattened venter and a proportionally large verntral siphuncle, 0.15...
, Sactorthoceras, Scipioceras, Sigmocycloceras
Sigmocycloceras
Sigmocycloceras is a nautiloid cephalopod discovered in the Middle Ordovician of Korea, said to be similar to Sactorthoceras, and included in the Sactorthoceratidae, but unique in being longitudinally sigmoid and sculpted with transverse annuli....
, Wennanoceras, and Wolungoceras, with the Sactorthoceratade 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
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 slender and orthoconic. The siphuncle is central or...
in the Treatise (Sweet, 1964); Cartersoceras and Murrayoceras in the Baltoceratidae
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, existing for approximately .-Taxonomy:Baltoceratidae was...
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.