Sinclairoceras

Systematic Paleontology

Class Cephalopoda

Subclass Nautiloidea

Order Discosorida

Family Westonoceratidae

Genus Sinclairoceras

Sinclairoceras is a discosorid nautiloid included in the Westonoceratidae from the middle Ordovician of Quebec. The shell is compresed, the dorsal outline only slightly concave, the ventral outline strongly convex. Curvature, as for the family, is exogastric. The anterior part of the phragmocone, closest to the body chamber, is strongly humped; the body chamber contracted, aperture sloping  from dorsum to venter, the hyponomic sinus slight. The siphuncle which is close to the venter has broadly expanded segments and thick connecting rings.

Shell morphology suggests that Sinclairoceras lived facing forward, reaching out for its prey, the convex venter closest to the sea bed. Nothing is known of its soft part anatomy.

Sinclairoceras probably has its origin in Ulrichoceras, or the like.