Foraminiferans are unicellular eukaryotes (protists) characterized by an extendable granuloreticulose pseudopodial net used in feeding, locomotion and other life processes. They are ubiquitous in aquatic environments, from terrestrial moist soils to the deepest parts of the ocean. They play an important role in ecosystem functioning and biogeochemical cycling, modifying the sediment structure, providing refuges and substrates for metazoans and other foraminiferans, influencing particle depositions on the seafloor, preventing larval settlement, and in some cases out-competing metazoans for scarce sources.

They are main primary consumers of organic matter reaching the seafloor and play an important role in benthic food webs and the carbon cycle. Recent studies have revealed that some species are able to survive under high pCO2 concentrations in the laboratory making these potential survivors in a high CO2 world. Foraminifera, including soft-shelled species, are one of these underrepresented groups and need to be included in any consideration of local and global biodiversity. Besides being abundant and diverse in modern oceans, primitive foraminiferans and related protists could have been an important component of the late Neoproterozoic biota.

Recent research shows that gromiids leave traces on the seabed, challenging the idea that metazoans appeared this early in the Earth´s history. Moreover, it has been suggested that the trace fossil Paleodictyon, represented on the modern ocean floor by enigmatic patterns of holes and subsurface burrows, is made by giant foraminiferans called xenophyophores.