Fusulins

Part of speech: noun

Definitions

1. Microscopic, elongated single-celled organisms with complex internal structures, commonly found as fossils in limestone formations; extinct marine protozoans contributing to geological studies of ancient environments
2. Fossilized forms of ancient spindle-shaped microorganisms with chambered shells, significant for their role in paleontological research and stratigraphic dating; once thriving in prehistoric seas as part of the marine ecosystem
3. Extinct single-celled protists characterized by their fusiform shells and intricate internal divisions, typically preserved within sedimentary rock and used to interpret Earth's geological past

Etymology: "Fusulins" is the plural of "fusulin," a name for members of the extinct group of single-celled organisms known as fusulinids. The singular comes from the genus name "Fusulina," which was formed in Latin-style Latinized form from "fusus," meaning "spindle," a reference to the spindle-shaped outline of the shells. The "-ulina" ending is a diminutive, a common pattern in scientific naming for small or slender things, so the name roughly means "little spindle." Fusulins are among the most useful fossils for dating rocks from the Carboniferous and Permian periods, because they evolved quickly and were widespread in shallow seas. Their shells, which grew more elaborate over time, help geologists match rock layers across distant regions.