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

Belongs within: Michelinoceratida.

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] S64
    |--Troedssonella Kobayashi 1935 S64
    |    `--*T. endoceroides (Troedsson 1932) [=Polygrammoceras endoceroides] S64
    |--Glenisteroceras Flower in Flower & Teichert 1957 S64
    |    `--*G. obscurum Flower in Flower & Teichert 1957 S64
    |--Oxfordoceras Ulrich, Foerste et al. 1944 S64
    |    `--*O. billingsi Ulrich, Foerste et al. 1944 S64
    |--Wolungoceras Kobayashi 1931 S64
    |    `--*W. foerstei Kobayashi 1931 S64
    `--Buttsoceras Ulrich & Foerste 1933 S64
         |--*B. adamsi (Butts 1926) [=Orthoceras adamsi] S64
         |--B. odenvillense Ulrich, Foerste et al. 1944 P68
         `--B. vandiverense Ulrich, Foerste et al. 1944 P68

*Type species of generic name indicated


[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 Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K216-K261. The Geological Society of America and the University of Kansas Press.

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