The internal plaits of the Nerineoidea had different functions: the columellar plaits subdivided the columellar muscle into strands, which allowed portions of the foot to be moved individually. A tubelike space delimited by the parietal and palatal plaits is compared with the pallial caecum or posterior mantle chamber of heterobranchs and served the respiration. Waste from both mantle chambers was expelled through a subsutural notch, which is the common feature of the Nerineoidea. The Nerineoidea were shell draggers and probably deposit feeders with a semi-infaunal mode of life. The "Lower Heterobranchia" represented by the Streptacidoidea Knight, 1931, Nerineoidea and Acteonelloidea Akopjan, 1976 cluster outside the Euthyneura Knight, 1931. The Acteonelloidea, the second group of large Heterobranchia are related to the Nerineoidea and cannot be part of the Acteonoidea. The extinction of the Eunerineidae n. fam., the Ptygmatididae and Ceritellidae in the Late Cenomanian was caused by a general warming in low latitudes. The Acteonellidae genus Trochactaeon Meek, 1863 replaced the extinct Eunerineidae n. fam. ecologically in shallow marine soft-bottom environments and became extinct itself in the Lower Campanian due to the general cooling. In the Caribbean palaeobiological province, the endemic Nerineoidea genus Plesioptygmatis Boese, 1906 extended stratigraphically to the basal Late Maastrichtian. Acteonella d'Orbigny, 1842 and the endemic Acteonellidae genus Mexicotrochactaeon Akopjan, 1972 ranged upwards into the Late Maastrichtian.

The results of detailed biostratigraphic, lithological, isotopic-geochemical, and petromagnetic analysis of the sedimentary sequence at the Cretaceous-Paleogene boundary in the Gams area, Eastern Alps, Austria, point to two stages in the evolution of the transitional layer at the Cretaceous-Paleogene boundary. During the earlier one of these stages (which lasted for approximately 1500 years, as follows from conservative estimates of the sedimentation rate), the transitional layer was formed under the effect of volcanic aerosol. The later one caused the presence of titanomagnetite, gold, and copper, as well as high concentrations of Ir, As, Pb, Cr, and other elements in the rocks. The occurrence of an Ir anomaly in the lower part of the transitional layer and the presence of titanomagnetite, Cu, and Au in it were related to volcanic activity. During the later stage, the character of sedimentation was affected by the fall of an asteroid (meteorite), and traces of its material are discernible as beads of metallic Ni, awaruite, and diamond crystals. The conclusions drawn from the results of our analysis principally differ from all preexisting data on the transitional layer between the Cretaceous and Paleogene and provide another look at the reasons for the mass extinction of living organisms at 65 Ma. These data eliminate the need for opposing volcanism to an impact event: both took place, but the changes in the biota were induced by volcanism, as also was the appearance of the Ir anomaly itself, whereas the fall of a cosmic body occurred approximately 500-800 years later.

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This catalogue illustrates 257 gastropod taxa from Paleocene deposits on the Nûgssuaq peninsula, West Greenland. Mesogastropods and neogastropods dominate, with 103 and 86 taxa respectively. There are 38 archaeogastropod taxa and 29 of Euthyneura, while one operculum is of unknown systematic position. Taxa are named at the generic level; no new names are introduced. Most of the fauna was collected from a single bed (Sonja Lens) within the Sonja Member of the Agatdal Formation. Faunal composition within this bed indicates a mixed assemblage with representatives from a variety of environments ranging from terrestrial (1 taxon) to shallow and deep marine, on soft and hard substrates.

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