Late Cretaceous elasmobranch palaeoecology in NW Europe

Late Cretaceous elasmobranch faunas are known from numerous of NW Europe localities but their palaeoecological characteristics are still poorly known. Recent studies on Anglo-Paris Basin elasmobranch faunas from phosphatic chalks provided detailed data on the taxonomic composition of these communities. Results based on multiproxy analyses suggest peculiar conditions for Cenomanian faunas with numerous lamniforms and rare nectobenthic taxa indicative of dysoxic conditions. Changes in Turonian faunal composition correlate with a maximum in palaeotemperatures and transgressive environmental conditions. The northern Coniacian glauconitic palaeoenvironment provided cooler and shallow environments suitable for a few species with probable migration patterns. A model is proposed to explain the ecological features of the Santonian–Campanian faunas in which the habitat heterogeneity is the main factor controlling elasmobranch diversity and evenness. The dominance of small-sized species in Santonian–Campanian faunas is similar to the patterns observed in modern upwelling environments. Low beta diversity of early Campanian faunas suggests that although faunas were from disjunct upwelling erosional channels, the number of such palaeoenvironments provided a wide range of habitats allowing species to migrate depending on local ecological conditions. The Santonian/Campanian global cooling is synchronous with changes in faunal compositions. Larger-scale palaeoecological, palaeoenvironmental and palaeogeographical patterns are proposed based on comparisons with a number of other NW Europe elasmobranch faunas