Microfossils: Foraminifera

The term ‘Foraminifera’ is derived from the Latin foramen, little hole and ferre, to carry or bear. They are a phylum of predominantly marine heterotrophic testate protozoans with tubular mitochondrial cristae and granuloreticular pseudopodia emanating from one or more openings in their tests. With over 50 000 known fossil and living species, the foraminifera constitute a diverse and geologically long-ranging group of organisms found in virtually all marine habitats. Morphologically, they form a heterogeneous and perhaps polyphyletic group with a fossil record that begins in the latest Precambrian, though forms with organic or unmineralised tests probably existed earlier. The group as a whole is characterised by the presence of an organic, agglutinated, or secreted biomineralised test partially enclosing the amoeboid body. The test may be single-chambered, pseudocolonial, pseudo-chambered, or multichambered with interconnected chambers added as the cell grows. Openings between the chambers [foramens] allow the cytoplasm to flow freely, while one or more apertures enable the cell to communicate with its external environment. A pseudopodial network may arise from a single apertural opening forming a distinct pseudopodial trunk or radiate in all directions from numerous openings or pores in the walls of some calcareous taxa. Pseudopodia exhibit bidirectional streaming, and are used for locomotion in free-living taxa, to anchor attached forms to the substrate, to capture and ingest food items, or to build new chambers and growth or reproductive cysts. Reproduction is remarkably complex, and typically involves an alternation of generations between a multinucleate diploid [agamontic] asexually reproducing stage and....