Fusulinacean

Part of speech: noun, adjective

Definitions

1. A type of extinct single-celled organism belonging to the foraminifera group, characterized by a shell called a test, often used in biostratigraphy to date rock layers
2. A fossilized unicellular creature with a distinct multi-chambered shell, part of the larger group of foraminifera, important for studying geological time periods
3. An ancient foraminiferan species recognized by its calcareous shell composed of multiple compartments, serving as an index fossil in paleontological research

Etymology: Fusulinacean is a formal taxonomic term, built from the genus name "Fusulina" plus the suffix "-acean," which zoologists and paleontologists use to form names for members of a superfamily (here, the Fusulinacea). The genus itself was named in 1844 by the German naturalist Hermann von Meyer, who based it on the spindle-shaped, rice-grain-sized fossils he found in Carboniferous limestone. The name comes from the Latin "fusus," meaning "spindle," a reference to the characteristic shape of these shells. The organisms are foraminifera, single-celled protists that build shells, and fusulinaceans were among the largest of them, with some individuals reaching several centimetres long. Their shells are made of carefully layered, spiral-coiled chambers, which made them valuable index fossils: because they evolved quickly and were widespread across the oceans during the late Paleozoic era, geologists used them to date rock layers. The group died out at the end of the Permian period, roughly 252 million years ago.

Synonyms: fusulinid