Sinclairoceras
Encyclopedia
Sinclairoceras is a nautiloid cephalopod in the discosorid family Westonoceratidae from the Middle Ordovician Simard Limestone of Quebec. The shell is a compressed exogastric brevicone with venter narrowly and dorsum broadly rounded. The dorsum, at the upper surface, is only slightly concave longitudinally. The venter, at the lower surface, is more strongly convex longitudinally, drawing away from the dorsum and forming a hump at the anterior end of the phragmocone where Sinclairoceras reaches its greatest width.
The upper and lower sides of the body chamber are essentially straight and virtually parallel, flairing slightly at the aperture. The sides however converge on the aperture which is laterally narrowed, flairing just before.
The siphuncle is near the venter. Segments are broadly expanded and broadly rounded, differing from the more narrow segmments of Simardoceras
but similar in outline to those of Reedsoceras
.
Sinclairoceras differs from the overall similar Westonoceras
is being shorter and less markedly swollen at the mature end of the phragmocone. It is found associated with Simardoceras and Reedsoceras with which it may be closely related.
The upper and lower sides of the body chamber are essentially straight and virtually parallel, flairing slightly at the aperture. The sides however converge on the aperture which is laterally narrowed, flairing just before.
The siphuncle is near the venter. Segments are broadly expanded and broadly rounded, differing from the more narrow segmments of Simardoceras
Simardoceras
Simardoceras is a genus in the discosorid family Westonoceratidae from the Middle Ordovician of Quebec.The shell of Simardoceras is a moderately expanding exogastric cyrtocone, said to resemble a rather large Oncoceras, but with a siphuncle that is definitely discosorid. The venter is almost...
but similar in outline to those of Reedsoceras
Reedsoceras
Reedsoceras is a large member of the discosorid family Westonoceratidae from the middle and upper Ordovician of North America....
.
Sinclairoceras differs from the overall similar Westonoceras
Westonoceras
Westonoceras is an extinct nautiloid genus from the Discosorida that lived during the Middle and Late Ordovician that has been found in North America, Greenland, and Northern Europe...
is being shorter and less markedly swollen at the mature end of the phragmocone. It is found associated with Simardoceras and Reedsoceras with which it may be closely related.
References
- Flower, R.H.and Curt Teichert 1957. The Cephalopod Order Discosorida. University of Kansas Paleontological Contributions, Mollusca, Article 6. July 1957
- Teichert, C 1964. Nautiloidea -Discosorida. Treatise on Invertebrate Paleontology Part K. Geological Soc of America and Univ. Kansas Press