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.) nec Quenstedt 1857 nec Meek 1876]S64
    |--*S. crotalum (Hall 1861) [=Orthoceras crotalum]S64
    |--S. anellusP68
    |--S. baffinenseP68
    |--S. barbense Foerste 1936P68
    |--S. bilineatum [=Orthoceras (Spyroceras) bilineatum]P68
    |    |--S. b. bilineatumP68
    |    `--‘Orthoceras’ b. frankfortensis Foerste 1910P68
    |--S. distoannulatum Foerste 1935P68
    |--S. jamesi [=Orthoceras (Spyroceras) jamesi]P68
    |--S. mcfarlani Foerste 1932P68
    |--S. microtextile Foerste 1923P68
    `--S. whitcombi Foerste 1932P68

*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: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K216–K261. The Geological Society of America and the University of Kansas Press.

Leave a comment

Your email address will not be published. Required fields are marked *