The Fusulinida is an extinct order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 within the Foraminifera

Foraminifera

The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

 in which the tests (shells) are composed of tightly packed, secreted microgranular calcite. In advanced forms the test

Test (biology)

A test is a term used to refer to the shell of sea urchins, and also the shell of certain microorganisms, such as testate foraminifera and testate amoebae....

 wall is differentiated into two or more layers. Loeblich and Tappan, 1988, gives a range from the Lower Silurian to the Upper Permian, although in the Treatise

Treatise on Invertebrate Paleontology

The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...

, 1964, it is given from the Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 to the Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

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Taxonomy

Thirteen superfamilies are presently recognised, based on taxa (families) included in the three superfamilies given in the Treatise. Three are based on families in the Parathuramminacea, 1964, and nine on families in the Endothyracea, 1964. The Fusulinacea remains the same in both sources (Treatise 1964 and Loeblich and Tappan, 1988).

Terminology

The term, "fusulinid" really applies to any of the Fusulinida. The Fusulinida are fusulinids ( sensu latu). However the term "fusulinid" is often applied just to the fusiform Fusulinacea, and not to the entire order.

Application

Members, especially of the Fusulinacea, are excellent guide fossils for determining ages and correlating Upper Mississippian to Permian strata. In some places fusulinaceans may be so abundant as to be a significant component of limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

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