Retaria

Retaria is a major clade within the supergroup Rhizaria, comprising two extant phyla: Radiolaria and Foraminifera. The name derives from Latin reticulum, meaning “net,” in reference to their characteristic reticulopodial or net-like feeding networks.

Characteristics of Retaria include being unicellular eukaryotes that often produce elaborate mineral skeletons. Radiolaria possess silica-based tests and cytoskeleton-supported axopodia, which are long, slender pseudopodia reinforced by microtubules used for capture and locomotion. Foraminifera produce calcium carbonate or agglutinated tests and extend reticulopodia—net-like networks of pseudopodia used to capture food particles and to move. These features support diverse feeding strategies in marine environments.

Ecology and diversity: Retaria species are predominantly marine. Many radiolarians and foraminiferans are planktonic, forming part of the marine zooplankton, while benthic foraminiferans inhabit sediments on the seafloor. The group includes thousands of species with a wide range of body plans and test architectures.

Fossil record and significance: Foraminifera and radiolarians have long fossil records dating back to the early Paleozoic. Their tests are widely used in biostratigraphy and palaeoclimatology, helping to reconstruct ancient ocean conditions and geological timelines.

Taxonomy and relationship: Within Rhizaria, Retaria is a principal clade that divides into Radiolaria and Foraminifera. Molecular and paleontological data support their unified grouping under Retaria, despite differences in skeletal chemistry and morphology.

Etymology: The name Retaria reflects the net-like pseudopodial systems characteristic of the group.