Aphetoceras

Taxobox
fossil_range = L Ordovician (late Canad)
name = " Aphetoceras "


regnum = Animalia
phylum = Mollusca
classis = Cephalopoda
subclassis = Nautiloidea
ordo = Tarphycerida
familia = Estonioceratidae
genus = " Aphetoceras "
genus_authority = Hyatt, 1894

"Aphetoceras"; a genus of Tarphycerida within the Estonioceratidae; loosely coiled without an impression along the dorsal margin; early whorls barely teaching, separating then diverging in the final mature whorl; weakly ribbed in some. The cross section of "Aphetoceras" is higher than wide, making it compressed in form. The dorsum, along the inner curve, is more broadly rounded than the venter which lies along the outer curve. The siphuncle is relatively large, located near but not at the ventral margin; lined with secondary deposits. Chambers are empty.

"Aphetoceras" is similar in outline to the related "Estonioceras" and "Alaskoceras" but most similar in cross section to "Clytoceras".

"Aphetoceras" comes from the Lower Ordovician of North America and Australia and is one of the earlier tarphycerids found in the Lower Ordovician El Paso Group in New Mexico.

References

*Aphetoceras, p K358 in Vol K of the Treatise on Invertebrate Paleontology in the section on the Estonioceratidae, p K357-K359, included in the Chapter on the Tarphycerida by Furnish and Glenister starting with page K343.