orthoconic

Plenum Press, New York. Chapter 1, pp. 3-19. Gabbott, Sarah E. 1999. Orthoconic cephalopods and associated fauna from the Late Ordovician Soom Shale Lagerstätte

Invertebrates diversify into many new types (e.g., long straight-shelled（英语：orthoconic） cephalopods（英语：orthocerida）). Early corals, articulate brachiopods (Orthida