External and sectional views of Troedssonella endoceroides, from Sweet (1964).

Belongs within: Orthoceratia.

The Troedssonellidae were a Lower to Middle Ordovician family of orthocerid cephalopods that formed endocones in the apical part of their siphuncles.

Characters (from Sweet 1964): Siphuncle suborthochoanitic; continual endosiphuncular lining of parietal deposits prolonged adapically to form endocones.

Troedssonellidae [Buttsoceratidae, Troedssonellina]S64
|--Tajaroceras wardae Hook & Flower 1976K93
|--Moridunoceras Evans 2005KE19
|--Oxfordoceras Ulrich, Foerste et al. 1944S64
| `--*O. billingsi Ulrich, Foerste et al. 1944S64
|--Wolungoceras Kobayashi 1931S64
| |--*W. foerstei Kobayashi 1931S64
| `--W. chiushuense Kobayashi 1933CT83
|--Troedssonella Kobayashi 1935S64
| |--*T. endoceroides (Troedsson 1932) [=Polygrammoceras endoceroides]S64
| `--T. huanense Lai & Tsi 1977K93
`--Buttsoceras Ulrich & Foerste 1933KE19
|--*B. adamsi (Butts 1926) [=Orthoceras adamsi]S64
|--B. odenvillense Ulrich, Foerste et al. 1944P68
`--B. vandiverense Ulrich, Foerste et al. 1944P68

*Type species of generic name indicated


[CT83] Chen J.-Y. & C. Teichert. 1983. Cambrian Cephalopoda of China. Palaeontographica Abteilung A: Paläozoologie—Stratigraphie 181 (1–3): 1–102.

[K93] King, A. H. 1993. Mollusca: Cephalopoda (Nautiloidea). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 169–188. Chapman & Hall: London.

[KE19] King, A. H., & D. H. Evans. 2019. High-level classification of the nautiloid cephalopods: a proposal for the revision of the Treatise Part K. Swiss Journal of Palaeontology 138: 65–85.

[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.

[S64] Sweet, W. C. 1964. Nautiloidea—Orthocerida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. Cephalopoda—General Features—Endoceratoidea—Actinoceratoidea—Nautiloidea—Bactritoidea pp. K216–K261. The Geological Society of America and the University of Kansas Press.

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