Microfossils (Foraminifera)

These are mostly simple single-celled creatures with a protective shell or test. They range from size 1um to around 110mm. Early forms had tests of particles glued together for protection, while more advanced forms secrete an amazing diversity of shells. Modern formanifera capture their food using thread-like structures, which extend through holes in the test. Most forms are benthonic but a few such as Glabigerina are planktonic.

They range from early Cambrian to the present day, although the common forms were not common until the Mesozoic. This group has proven to be an excellent stratigraphic tool used extensively in the oil industry. Research has enabled detailed ranges to be determined for many different species. This also provides evidence of how evolutionary changes occur.