Foraminifera

Benthic foram Planulinoides biconcavus from Bass Strait.

Foraminifera, or forams, belong to a group of single-celled animals (protozoans) that form calcareous shells. These shells are mostly microscopic, ranging from 0.5 to 1.0 millimetre, although some grow to several centimetres in size.

Foraminifera are found in all depths of brackish and marine water today. They include benthic (bottom-living) forms living on or in the sediment and planktic forms floating near the surface of the water.

Benthic forams have a long fossil record extending back to the Cambrian (about 545 to 490 million years ago). They are particularly useful in determining ancient depositional environments and for dating rocks.

Planktic forams evolved in the Mesozoic Era (251 to 65 million years ago). They were almost wiped out in the mass extinctions at the end of that era (65 million years ago), but recovered in an adaptive radiation early in the Cainozoic (65 million years ago to present). They are very important for the correlation and dating of rocks in the Cainozoic because of their rapid evolution and worldwide distribution.

Forams are very common in the Tertiary clays that occur along Victoria's southern coast.

Benthic foram Elphidium crispum from Bass Strait.

Benthic foram Cibicides cygnorum from Bass Strait, common in Victoria.

Planktic foram Turborotalia inflata from Bass Strait, moderately common in Victorian waters.