Lambeoceras is a genus of large actinocerids with a convexly lenticular cross section from the Upper Ordovician of North America and the sole representative of the family Lambeoceratidae.
Lambeoceras is of medium to moderately large size with a long, straight, depressed shell, broad in cross section with the dorsum and venter both about equally convex, meeting acutely along the sides.
Actinoceras, and Selkirkoceras in the overlying dolomite – all of Red River age, marking the transition between the Middle and Upper Ordovician.
While the earlier Gonioceras no doubt rested on the sea floor in ambush, perhaps half buried or more in sediment, Lambeoceras may have more actively hunted in the water close to but above.
On the other hand, Lambeoceras ' shape may have had more to do with stabilization in shallow surge ridden waters than with hunting methods.