Acritarchs are an artificial group of microfossils, and their name, originally coined by Evitt, literally means “of uncertain origin”. This group contains organic-walled microfossils which range from about 20-150 microns in length that cannot be assigned to another group (MIRACLE, n.d.). Acritarchs include the remains of many small organisms, including egg cases as well as cysts of algae (Search.com Reference). As such, they may represent the earliest fossilized remains of eukaryotic cells, dating to 2.1 bya (Smithsonian Institution). Some of these cysts are believed to be those of dinoflagelates, but others are known to have cholorphyte origin (SAO). They were abundant over 1.8 billion years ago and are still around today as well, although since the Devonian period they have decreased. There are many different forms of acritarchs- they come in all different shapes, sizes, and textures from smooth, spiny, egg-shaped, fusiform, serrated, and polygonal. Yet, there is not a set classification for the different forms; most just use the ones created by Downie, Evitt, and Serjeant. These include the Acanthomorphs, Polygonomorphs, Netromorphs, Diacromorphs, Prismatomorphs, Oomorphs, Herkomorphs, Pteromorphs, and Spaeromorphs. Acrtitarchs are also stratigraphically useful in the Upper Proterozoic to the Permian ages (MIRACLE). They are important because they help play a role in the evolution of the marine ecosystem since they are at the bottom of the food chain (SAO).

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SAO/NASA ADS. Accessed January 14, 2010.

Search.com Reference. Accessed January 15, 2010