Discoceras
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| Discoceras Fossil range: M-U Ordovician |
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Discoceras, a member of the Trocholitidae in the Tarphycerida, not to be confused with Discosorus.
Discoceras is characterized by closely coiled, gradually expanding shells with a subquadrate cross section, that may be ribbed or smooth. The sides are broadly rounded; the venter wide and slightly rounded. The maximum width is slightly dorsal of the middle. The dorsum has a slight to moderate impression. The siphuncle starts off central for the first half whorl then becomes marginodorsal in the succeeding 1.5 to 2 whorls, then subdorsal at maturity. As with Trocholites the dorsal siphuncle in Discoceras probably indicates an orientation during life that places the back of the living chamber high in the shell.
Discoceras has been found in Middle and Upper Ordovician sediments in Northern Europe, Baffin Island in Canada, Yunnan and Hopeh provinces in China, and in Punjab, India.
[edit] Reference.
- Discoceras, p K360 in Vol K of the Treatise on Invertebrate Paleontology in the section on the Trocholitidae,ppK359-K362, in the Chapter on the Tarphycerida by Furnish and Glenister starting with page K343.
