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 microfossil
s, and are classified as palynomorph
s, 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.