New Latin Fusulinidae, from Fusulina, a genus, from Latin fusus spindle + -ulus -ule + New Latin -ina, diminutive suffix
First Known Use: 1941
Any of a large group of extinct foraminiferans, single-celled organisms related to amoebas but having complex shells that are easily preserved as fossils. The fusulinids first appeared during the Carboniferous period, perhaps c. 320 million years ago, and persisted until the end of the Permian period, 248 million years ago. They have been extremely useful for correlating different rock units in widely separated regions and for dividing geologic time into smaller units. Petroleum geologists also use them to help locate economically valuable deposits of oil and natural gas.