Cross-sections of the Lower Carboniferous Carbactinoceras torleyi, showing the distribution of endosiphuncular and cameral deposits. Figure from Teichert (1964).

Belongs within: Actinocerida.

The ormoceratid lineage of actinocerid cephalopods (including the families Ormoceratidae [paraphyletic] and Carbactinoceratidae) lived from the Middle Ordovician to the Upper Carboniferous.

Characters (from Teichert 1964): Generally straight (some Carbactinoceratidae slightly curved) medium-sized to very large shells, circular or subcircular cross-section. Siphuncle central or subcentral, one-fifth or less of shell diameter in early forms, large in Carbactinoceratidae; septal necks varying from long, cyrtochoanitic to recumbent; siphuncle segments generally globular or longer than broad, rarely broader than long; endosiphuncular canal system simple, radial canals generally perpendicular to central canal. Cameral deposits not common in early forms, filling most chambers in large part of phragmocone in Carbactinoceratidae.

<==Ormoceratidae [Deiroceratidae, Eskimoceratidae, Sactoceratidae, Troedssonoceratidae]
    |  i. s.: Eskimoceras Troedsson 1936 T64b
    |           `--*E. boreale Troedsson 1936 T64b
    |         Mstikhinoceras Shimanskiy 1961 T64b
    |           `--*M. mirabile Shimanskiy 1961 T64b
    |--Orthonybyoceras Shimizu & Obata 1935 (see below for synonymy) T64b
    |    |--*O. covingtonense (Foerste & Teichert 1930) [=Ormoceras covingtonense] T64b
    |    |--O. cannonense T64b
    |    |--‘Orthoceras (Euorthoceras)’ hanoverense Foerste 1889 P68
    |    |--‘Orthoceras (Euorthoceras)’ ignotum P68
    |    `--‘Orthoceras (Euorthoceras)’ rectum [incl. O. r. var. junior Foerste 1890, O. r. var. junius] P68
    `--+--Parormoceras Shimizu & Obata 1935 T64b
       |    `--*P. nanum (Brabau 1922) [=Actinoceras nanum] T64b
       `--+--Deiroceras Hyatt 1884 T64b
          |    |-*D. python (Billings 1857) [=Orthoceras python] T64b
          |    |--D. capitolense Foerste & Teichert 1930 P68
          |    |--D. curdsvillense Foerste & Teichert 1930 P68
          |    |--D. dismukesense Foerste & Teichert 1930 P68
          |    |--D. nashvillense Foerste & Teichert 1930 P68
          |    |--D. remotiseptum T64b
          |    `--D. richteri Foerste & Teichert 1930 P68
          `--+--Troedssonoceras Foerste 1928 [=Troendssonoceras (l. c.)] T64b
             |    |--*T. turbidum (Hall & Whitfield 1875) [=Orthoceras turbidum] T64b
             |    `--T. baileyi Flower 1939
             `--+--+--Metarmenoceras Flower 1940 T64b
                |  |    `--*M. bilaterale Flower 1940 T64b
                |  `--Carbactinoceratidae T64b
                |       |--Aploceras d’Orbigny 1849 [=Haploceras Saemann 1853] T64b
                |       |    `--*A. verneuilianum (de Koninck 1844) [=Cyrtoceras verneuilianum] T64b
                |       |--Carbactinoceras Schindewolf 1935 T64b
                |       |    `--*C. torleyi Schindewolf 1935 T64b
                |       `--Rayonnoceras Croneis 1926 T64b
                |            |--*R. solidiforme Croneis 1926 T64b
                |            |--R. bassleri Foerste & Teichert 1930 P68
                |            |--R. buffaloense Foerste & Teichert 1930 P68
                |            |--R. girtyi Foerste & Teichert 1930 P68
                |            |--R. rangifer Gordon 1957 P68
                |            `--R. vaughanianum P68
                `--Ormoceras Stokes 1840 (see below for synonymy) T64b
                     |--*O. bayfieldi Stokes 1840 T64b
                     |--O. actinoceriforme D82
                     |--O. allumettense T64b
                     |--O. billingsi T64b
                     |--O. cannonense Foerste & Teichert 1930 P68
                     |--O. chinense Endo 1932 P68
                     |--‘Sactoceras’ depressum Foerste 1930 P68
                     |--O. ferecentricum Foerste & Teichert 1930 P68
                     |--O. hitzi (Foerste 1910) [=Orthoceras (Ormoceras) hitzi] P68
                     |--O. holmi T64b
                     |--‘Sactoceras’ inaii Endo 1923 P68
                     |--O. kimurai Endo 1932 P68
                     |--O. lindseyi Foerste & Teichert 1930 P68
                     |--O. manchuriense Endo 1932 P68
                     |--O. nagaoi Endo 1932 P68
                     |--O. neumani Flower 1957 P68
                     |--O. normanense Foerste & Teichert 1930 P68
                     |--O. orientale Endo 1932 P68
                     |--O. pellucidum T64a
                     |--O. proximum Endo 1932 P68
                     |--O. taii Endo 1932 P68
                     |--O. taitzuense Endo 1932 P68
                     `--O. troosti Foerste & Teichert 1930 P68

Ormoceras Stokes 1840 [=Hormoceras Agassiz 1846, Ormoceratites (l. c.); incl. Adamsoceras Flower 1957, Aluveroceras Balashov 1955, Sactoceras Hyatt 1884] T64b

Shimizu & Obata 1935 [incl. Euhuronia Shimizu & Obata 1936, Euormoceras Shimizu & Obata 1936, Euorthoceras Foerste 1893, Siberioceras Zhuravleva 1957, Treptoceras Flower 1942] T64b

*Type species of generic name indicated


[D82] Dong D.-Y. 1982. Lower Ordovician stromatoporoids of northern Anhui. Acta Palaeontologica Sinica 21 (5): 577-583.

[P68] Purnell, L. R. 1968. Catalog of the Type Specimens of Invertebrate Fossils. Part I: Paleozoic Cephalopoda. United States National Museum Bulletin 262: 1-198.

[T64a] Teichert, C. 1964a. Morphology of hard parts. In Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K13-K53. The Geological Society of America and the University of Kansas Press.

[T64b] Teichert, C. 1964b. Actinoceratoidea. In Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K190-K216. The Geological Society of America and the University of Kansas Press.


  1. I like the new blog, although I'm glad the old Catalogue of Organisms is continuing.

    Regarding this post, the reference below argues that the carbactinoceratids actually evolved among the pseudorthocerids, and their resemblance to actinocerids is convergent.

    Kröger, Björn, & Mapes, Royal (2007). Actinoceratoid Nautiloidea (Cephalopoda) — A new perspective. Journal of Paleontology 81 (4): 714–724.

  2. Thanks for that, George. I get the impression that 'orthocerid' cephalopods, also discussed in the paper you pointed out to me, seem to be the most difficult group of cephalopods to pin down phylogenetically.

  3. There have been some efforts to sharpen the diagnosis of Orthocerida, but the group still seem phylogenetically elusive because they exhibit so much convergence.

    It would be good to sort out the evolutionary details of the orthocerids, since as a grade group they include the ancestors of ammonoids and coleoids via bactritids. Moreover, several specialists have suggested that they gave rise to the Nautilida as well:


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