A hollow marine unicellular organism, between 20 and 150 µm across, hollow with a hard organic outer cell wall. This is resistant to geological decay, so they survive as microfossils, and are classified as palynomorphs, that is fossil structures studied in palynology along with other hard microscopic parts such as the outer walls of pollen. Their exact genetic affinity is unknown. They might be some form of alga. Visually, they have numerous spikes on the outer surface.