Area cladograms produced by parsimony analysis of endemicity coupled with seriation, paired group cluster, principal coordinates, and detrended correspondence analyses demonstrate endemic associations of Mississippian-age bryozoans. These methods identified three major biogeographic associations (North America I, North America II, and Old World Realms), and nine minor associations (Waverly, Keokuk, Warsaw, Burlington, St. Louis, Chester, Tethys I, Tethys II, Russia, Kazakhstan-Siberia Provinces). These associations, along with latitudinal diversity gradients, provide support for an early closure of the tropical seaway (Rheic Ocean) that existed between Laurussia and Gondwana, along with support for faunal shifts due to the onset of Gondwanan glaciation and the restriction of North American faunas from the more eastern Tethyan faunas.
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