Clypeina

Clypeina is a genus of extinct algae belonging to the family Dasycladaceae. These marine green algae are characterized by their distinctive thallus structure, which is typically a long, slender, and segmented axis. Each segment is composed of a series of whorls of branches, giving the alga a bushy or feathery appearance. The calcified skeleton, which is what is preserved as fossils, often retains the imprint of these cellular structures.

Fossils of Clypeina are found in marine sedimentary rocks, primarily from the Mesozoic Era, particularly the Jurassic and Cretaceous periods. They are commonly found in shallow marine environments, indicating a preference for well-lit, warm waters. The distribution of Clypeina fossils suggests a widespread presence across various ancient marine basins.

The morphology of Clypeina species is often used for biostratigraphic correlation in geological studies. Their relatively short stratigraphic range and distinct features make them useful index fossils for dating rock layers. Several species have been described, differentiated mainly by the shape, size, and arrangement of their skeletal components, as well as the degree of calcification. The study of Clypeina contributes to our understanding of ancient marine ecosystems and the evolution of calcareous algae.