Back to: Nature online

Fossil dinoflagellate cyst

light microscope image of dinoflagellate

Modern dinoflagallates, found off the shore of South Africa, viewed by light microscopy.

light microscope image of dinoflagellate

A Confocal Laser Scanning Microscope was used to image this microscopic animal. Very thin optical sections (images) are taken, as in computer tomography (CT scans). These images are then re-composed on a computer to produce a 3D reconstruction. The movie is not complete because 'depth' information is limited to the optical section width and is therefore of low resolution.

Dinoflagellates are microscopic unicellular algae (plants), which populate the sea in huge numbers. They mostly belong to the phytoplankton, which live in the surface waters of the ocean and photosynthesise (like land plants). Hence they belong to the important group of 'primary producers' at the beginning of the food chain, serving as food for many larger creatures.

These cysts give a continuous abundant fossil record from many sedimentary rocks from the Upper Triassic Period onwards, so we know they have existed for more than 200 million years.

Moreover, the dinoflagellate cysts changed quickly during the Mesozoic Era and Cenozoic Era. They are therefore very good guide fossils and much used for age dating of sedimentary rocks (a technique called biostratigraphy). Dinoflagellate cyst biostratigraphy is especially widely used in exploration for oil or gas reservoirs.