Alamo's Tiny Bits: Formanifera
Fossil Invertebrates

Foraminifera (forams) are single celled animals of the Phylum Protista. They create tests made from secreted or agglutinated forms of the mineral calcite. These organisms come in many forms which are broadly divided into two groups: benthic and planktonic.

These two groupings are reflections of their mode of life. Benthic forams live on ocean floors and to biologists and paleontologists can be good indicators of water depth. Planktonic forams are those which make their tests into bulbous, buoyant, popcorn-like forms which allow them to remain suspended in the water column and travel along natural ocean currents. Planktonic forams are typically found in offshore marine sediments where the shells of deceased organisms pile up to form fine grained lime mud.

Both benthic and planktonic foraminifera are important rock builders, and although they were not yet at their peak in the Devonian Period, they can be found in some Guilmette Formation rocks when viewed under a microscope. The most notable occurrence of foraminifera as rock builders is probably the genus Nummulites which makes up the limestone from which the pyramids of Egypt are built.