Meandropsinidae, an ophtalmidid family of Late Cretaceous K-strategist foraminifera endemic in the Pyrenean Gulf

摘要

The Meandropsinids arc defined by their diaphanous umbo in their porcelaneous Shells that is always present at least in their microspheric generation. The extent of the development of their endoskeleton depends on the relative length of their apertural face of the spiral to annular chambers. The alar prolongations of the spiral chambers are Subdivided by ridges or complete septular walls arising from the basal layer of the chamber. These endoskeletal elements arc aligned in Subsequent chambers but interrupted by preseptal passages. All members of the family Meandropsinidae Occur within the Senonian and are restricted to the Late Cretaceous Pyrenean Gulf, except the most simple and small-sized members Nummofallotia and Eofallotia. In Spirapertolina and Larrazetia only microspheric specimens have been found. The large-sized members of the Meandropsinid family are interpreted as endemists in the Pyrenean Gulf in analogy to the larger sized representatives of the family Lacazinidae. The results of the structural analysis of the Meandropsinidae oblige to introduce the following new linnean names: Eofallotia simplex n. gen. n. sp., Fascispira schlumbergeri n. sp. and Alexina papyracea n. gen. n. sp.