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Two genera of fusulinids, Pseudoschwagerina and Paraschwagerina, long recognized as stratigraphic guides to Lower Permian beds, contain more than 100 species which can be grouped according to their morphological similarities and differences into twelve phylogenetic lineages. The primitive species complexes that initiated these lineages began near the beginning of the Permian in the Western Hemisphere. Their widespread migration and subsequent restriction led to the evolution of more advanced lineages of which several had times of widespread, but commonly brief, distribution.
The most primitive pseudo-schwagerinid complex, the Pseudoschwagerina beedei complex, arose from inflated Triticites ancestors probably in the Andean geosyncline. This complex gave rise to the P. uddeni complex, which attained both Eurasian and Western Hemisphere distribution, and the P. d'orbignyi complex which is known from South America and southern Europe. The P. heritschi, P. carniolica, and P. miharanoensis complexes are largely restricted to Eurasia or to small areas of the Eurasian fusulinid province. The ancestors of each of these three complexes are poorly known but they apparently arose from advanced species in the P. uddeni lineage. Both the P. yabei and P. stanislavi lineages appeared very late in the evolution of the genus. The P. yabei complex ranges into strata of Leon rdian age in southern Europe and Asia and the P. stanislavi complex occurs in strata of Leonardian age in Eurasia and North America.
The most primitive paraschwagerinid species complex, the Paraschwagerina gigantea complex, is apparently related to the genus Schwagerina but its ancestry is not well known and species of Schwagerina that would form typical ancestors for Paraschwagerina did not evolve until Paraschwagerina itself was nearly extinct. Of the younger and more advanced complexes, the P. plena
complex is restricted to western North America and the P. roveloi and P. endoi complexes are known from both North America and Asia.
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