Maastrichtian Ceratisepia and Mesozoic cuttlebone homeomorphs

The phylogenetics of potential Mesozoic ancestors of cuttlefish of a restri cted order Sepiida von Zittel, 1895 (superorder Decabrachia Boettger, 1952) is reviewed. Microstructural studies of Mesozoic homeomorphs of cuttlebone s (Pearceiteuthis gen. n., Loligosepia, Trachyteuthis, Actinosepia) are con sistent with their assignement to the superorder Octobrachia Fioroni, 1981. The discovery of an embryonic Ceratisepia shell in the upper Maastrichtian of the Netherlands, indicates that true Sepiida did have a pre-Cenozoic or igin. Cretaceous decabrachs of the order Spirulida Stolley, 1919 do not sho w evidence of the dorso-anterior shell growth vectors seen in Cenozoic spir ulids, sepiids and octobrachs. Separate origins of the Sepiida and Spirulid a within Cretaceous diplobelinid belemnites is still the most attractive hy pothesis. Ceratisepia vanknippenbergi sp. n. from the upper Maastrichtian o f the Netherlands and Pearceiteuthis buyi gen. et sp. n. from the Callovian of England are described.