North Sea Lituolid Foraminifera with complex inner structures: taxonomy, stratigraphy and evolutionary relationships

Abstract

Otwornice aglutynujące z rodziny Lituolidae z osadów trzeciorzędowych Morza Północnego; struktura wewnętrzna skorupki, taksonomia, stratygrafia i ewolucja The taxonomic, stratigraphie and inferred phylogenetic relationships of North Sea lituolid foraminifera with complex inner structures (i.e., the Subfamilies Cyclammininae and Spiropsamiinae ofthe Family Lituolidae) are reviewed. Five essentially Cenozoic evolutionary lineages are recognised, four (Subfamily Cyclammininae) appearing to have originated from Haplophragmoides or Veleroninoides (Subfamily Haplophragmoidinae), one (Subfamily Spiropsamiinae) from Eratidus (Subfamily Ammomarginulininae), and perhaps ultimately from Spiroplectammina (Subfamily Spiroplectammininae, Family Textulariidae). Selective synonymies, taxonomic notes and detailed documentations of North Sea distributions are appended. The evolution (and extinction) of the various complex lituolid species appears to be related to evolving palaeoenvironmental conditions mediated by tectono-eustasy. The most important time in terms of evolution was the late Palaeocene. Further work is recommended on the taxonomic and phylogenetic relationships between certain problem species, and on areas outside the North Sea. Further work is also recommended on the controls on the development of alveolar wall structure and cribrate apertures (i.e., whether evolutionary or environmental). Investigation of variations in these aspects of morphology along coeval transects from the margin to the centre of a basin would be highly instructive in this regard. Variations in other aspects of morphology with depth could also be investigated by this means. Investigation of possible temporal variations in depth distributions would have to be based around analyses of transects from successive time-slices.