The Fusulinacea is a superfamily within the Fusulinina (now often regared as an order, Fusulinida), that for the most part are the archtypical prolate, often fusform, fusulinids; although some early discoidal forms are included; some even flatten and spread out in the later growth stage.
As with the suborder (or order), the test, or shell, of the Fusulinacea is composed of secreted microgranular calcite which petrographically is typically distinct from matrix calcite. In fusulinaceans the test wall is typically in two to four layers. The basic layers are tectum and either diaphanotheca or kariotheca, tectum is to the outside, diaphanotheca or kariotheca are on the insde. A third and fourth thin dark layer may be present, outer and inner tectoria (singular tectorium). Diaphanotheca is relatively thick, amorphous and light colored. Kariotheca, which developed from diaphanotheca has an alveolar honeycomb structure, seen as narrow close-spaced pillars in sectional view.
Two basic groups are found within the Fusulinacea, those in which the chamber walls are variably fluted and those in which the chamber walls are straight and chambers are partially subdivided by secondary septa known as septula. Forms with fluted septa, by which chambers may be divided into chamberlets, are typical of the Pennsylvanian and earlier. Those instead with septula are characteristic of the Permian.
As presently defind, the Fusulinacea includes 7 families, distinguished by such things as general form and size, as well as details of the internal structures. They are the:
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Loeblich, Alfred R Jr. and Helen Tappan, 1964. Sarcodina Chiefly "Thecamoebians" and Foraminiferida; Treatise on Invertebrate Paleontology, part C Protista 2. Geological Society of America and University of Kansas Press. R.C. Moore (ed)
Loeblich, Alfred R Jr. and Helen Tappan, 1988. Forminiferal Genera and their Classification. Van Nostrand Reinhold, New York, N.Y.
Wilde, Garner L. Pennsylvanian-Permina Fusulinaceans of the Big Hatchet Mountains, New Mexico. New Mexico Museum of Natural History and Science Bulletin 38 (2006). Albuquerque, New Mexico.
Credits: Text and references; JM