Twelve Permian stages, each characterized by distinctive levels in ammonoid phylogeny, can now be defined; all have a geographic derivation in reference areas of the Urals, West Texas, Timor, Armenia, Pakistan, or

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south China. Four series (Sakmarian, Artinskian, Guadalupian, and Dzhulfian) correspond to a traditional zonation of the past half-century, except that the non-marine sequence of the Russian Platform is regarded as an impractical reference. No pronounced break exists within this series of faunas. There is a perceptible difference between Upper and Lower Permian, but the extinction of six familial groups and introduction of two at the end of the Wordian Stage (basal Upper Permian) marks the greatest numerical change. Despite these differences, the Wordian-Capitanian boundary lies within the known range of seven familial groups constituting all the common ammonoids of the Guadalupian Series. The ammonitic Perrinitidae and Cyclolobidae serve collectively as primary zonal indices throughout the Permian. Where perrinitids are lacking, as in the Ural sections, and cyclolobids are too rare to be effective references, an additional five or six evolving groups can be employed to supplement the regular index forms and substantiate a sequential arrangement.

Twenty-eight ammonoid stocks of familial or subfamilial rank are recognizable in the Permian. Eleven of these phylogenetic units are represented in the Upper Pennsylvanian, but only one transgresses the Triassic boundary (as now defined). Directly ancestral forms are known for an additional four familial groups introduced at the base of the Permian. Two such stocks continue into the Triassic under different familial designations.

Extensive sequences of Permian ammonoid faunas have been found at only a few areas. Those of the Sakmarian and Artinskian Series are best known in the type area of the Ural Mountain region and to a lesser extent in Texas. A knowledge of the Guadalupian Series is based largely upon a combination of sections in Coahuila and West Texas, although the most diverse single fauna is from Sicily. Timor Permian ammonoids span all of the system except the Upper (Dzhulfian) Series. Late Permian has its best development in the eastern Tethys region.

Most Permian ammonoid families were cosmopolitan and many species had a worldwide distribution. A few genera within the Artinskian Series were endemic. Also, some goniatitic genera appear to have persisted in high latitudes, but such a relationship is obscured by range extensions of other forms within the Tethyan Upper Permian.

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