Forams are similar to most species in the respect to how they evolved. They would experience explosive radiation and evolution, followed by mass extinction. The first known species of forams are from the Cambrian. This benthic foram was simple agglutinated tubes with only a single chamber. During the Devonian , the forams evolved to have multiple chambers and a few were calcareous. Calcareous forams began to really radiate in the Carboniferous. All Paleozoic forams were benthic. Planktonic forams did not evolve until the Mesozoic, and radiated several times during the Cenozoic. Like most organisms of the time, the mass extinction during the Permian killed thousands of species of forams.
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