Late Jurassic and Early Cretaceous uncoiled ammonites : trophism-related evolutionary processes

The polyphyletic suborder Ancyloceratina had an evolutionary success during the entire Cretaceous period. Protancyloceratinae appeared in Early Tithonian and Crioceratitinae during the Late Valanginian-Early Hauterivian transition. Eustatic variations or buoyancy efficiency are not related with the evolutionary success of these two lineages. Their evolution was favored by trophic opportunities created after important, palaeogeographic global changes.