Rotaliida

Rotaliida is a large and diverse order of foraminifera, which are single-celled eukaryotic microorganisms. Foraminifera are characterized by their shells, known as tests, which can be composed of various materials including calcium carbonate. The order Rotaliida encompasses a wide range of test morphologies, but many members exhibit planispiral or trochospiral coiling. The term "rotaliid" itself refers to this characteristic coiled structure. These organisms are found in a variety of marine environments, from shallow coastal waters to the deep sea, and play significant roles in marine ecosystems. Their fossilized tests are abundant in sedimentary rocks and are crucial for biostratigraphy, the dating of rock layers. Ecologically, rotaliids can be planktonic, floating in the water column, or benthic, living on the seafloor. Many species are heterotrophic, feeding on bacteria, algae, or other small organisms. Some rotaliids also host symbiotic algae within their tests, gaining nutrients through photosynthesis. The classification within Rotaliida is complex and has undergone revisions as new research and genetic analyses become available. Key families within the order include the Rotaliidae, Anomalinidae, and Cassidulinidae, each with distinct morphological and ecological features.