Ellipsoidina

Ellipsoidina is a genus of extinct microorganisms belonging to the foraminifera, a group of single-celled amoeboid protists that produce shells called tests. These fossils are primarily found in marine sedimentary rocks. The genus Ellipsoidina is characterized by its distinctive test morphology. The tests are typically elongate and fusiform, meaning they are widest in the middle and taper towards both ends, resembling an ellipse or a spindle. This shape is a key diagnostic feature used in paleontology for identification and classification.

The internal chambers of Ellipsoidina tests are arranged in a planispiral or streptospiral coiling pattern in the early growth stages, becoming more uniserial or biserial in later stages. The aperture, the opening through which the organism extended its pseudopodia, is usually a simple opening at the base of the final chamber. Ellipsoidina lived during the Cenozoic Era, with its fossil record spanning from the Paleocene to the Oligocene epochs. They inhabited shallow to moderately deep marine environments.

As microfossils, Ellipsoidina are valuable in biostratigraphy, aiding in the dating and correlation of rock layers. Their presence and abundance in sedimentary sequences can indicate specific paleoenvironmental conditions, such as water depth and salinity. The study of Ellipsoidina contributes to our understanding of past marine ecosystems and the evolutionary history of foraminifera.