Total extinction of fusulinacean foraminifera near the close of Permian time corresponds with extinctions among many families of Paleozoic animals. The tendency, however, is to think that these extinctions were rather abrupt, which carries a connotation of catastrophic biological revolution. Amongst the fusulinaceans, however, it can be demonstrated that the tendency toward extinction of the group had a rather early beginning accompanied by: (1) massive migrations away from former centers of proliferation, and (2) experimentation in shape, size, coiling, tunnel number and position, and shell composition. The absence of large genera, such as Polydiexodina, in latest Guadalupian rocks and the development of minute, complicated forms with possibly different shell compositions, point toward gradual, but extreme environmental changes. It is believed that these changes developed in response to geotectonic activity of a global nature. If it is true that continental masses were breaking up as early as Late Permian time, some knowledge of the loci of such pull-apart activity should help in reconstructing paleogeography for the time prior to the separation. Rather than making the picture more complicated, this reconstruction should help in deciding upon major stage boundaries within the Permian. Fusulinacean history offers important criteria for these boundary problems.

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Most fusulinid specialists have commonly regarded the Polydiexodina faunas of North America so coeval with those of Asia (Turkey, Afghanistan, etc.). The so-called Polydiexodina of southern Asia, however, corresponds more closely to Skinnerina, an Early Guadalupian (Wordian) genus. This is extremely important because the true Polydiexodina faunas of North America probably correlate with the Yabeina Zone of Japan. The minute Yabeina texana Skinner and Wilde, of the Lamar Limestone (Upper Capitan) of Texas and New Mexico, seemingly represents a late, dwarfed representative of the genus.

The Lepidolina Zone equivalent in North America is probably post-Guadalupian (Early Ochoan), and is represented only by the Paradoxiella-Paraboultonia-Codonofusiella-Reichelina faunas. Palaeofusulina has not been found in North America, and its occurrence with Codonofusiella and Reichelina elsewhere probably corresponds to the Late Ochoan (Late Dzhulfian) Stage.

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