15 cm long specimen of Spyroceras, from Penn Dixie.

Belongs within: Pseudorthoceratidae.

Spyroceras is a Devonian genus of orthocerid cephalopod recorded from Europe and North America.

Characters (from Sweet 1964): Annulated orthocones with straight transverse sutures, transverse or slightly oblique surface annulations, and faintly cyrtoconic apices. Surface variously ornamented, longitudinal lirae conspicuous from earliest stage. Siphuncle central or slightly ventral; siphuncle orthochoanitic with forward-growing endosiphuncular annuli; in mature segments, brims and necks subequal, longer than width of adnation area. Cameral deposits mural; cameral and siphuncular deposits restricted to more apical parts of the conch.

<==Spyroceras Hyatt 1884 [=Spiroceras (l. c.) non Ahlfield & BraniĊĦa 1960] S64
    |--*S. crotalum (Hall 1861) [=Orthoceras crotalum] S64
    |--S. anellus P68
    |--S. baffinense P68
    |--S. barbense Foerste 1936 P68
    |--S. bilineatum [=Orthoceras (Spyroceras) bilineatum] P68
    |    |--S. b. bilineatum P68
    |    `--‘Orthoceras’ b. frankfortensis Foerste 1910 P68
    |--S. distoannulatum Foerste 1935 P68
    |--S. jamesi [=Orthoceras (Spyroceras) jamesi] P68
    |--S. mcfarlani Foerste 1932 P68
    |--S. microtextile Foerste 1923 P68
    `--S. whitcombi Foerste 1932 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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