Rotalianidae

Rotalianidae is a family of foraminifera, which are single-celled organisms belonging to the Rhizaria supergroup. These marine protists are characterized by their shells, known as tests, which are typically planispiral or trochospiral in coiling. The family Rotalianidae is part of the order Rotaliida, a diverse group of foraminifera that are found globally in various marine environments, from shallow coastal waters to deep-sea sediments.

The test of Rotalianidae is often composed of calcite, a mineral form of calcium carbonate, and can exhibit a variety of surface textures, including smooth, costate, or tuberculate. The chambers are added sequentially as the organism grows, with new chambers enclosing the previous ones. The aperture, the opening through which the pseudopodia extend, is typically located at the base of the final chamber.

Fossil Rotalianidae are abundant in the fossil record, particularly from the Mesozoic and Cenozoic eras. Their diverse morphologies and widespread distribution make them valuable for biostratigraphy, helping to date rock layers and reconstruct past ocean conditions. While many species are extinct, some genera and species of Rotalianidae are still extant today, continuing to play a role in marine ecosystems. Their feeding habits generally involve trapping small plankton and organic particles using their pseudopodia.