THE EVOLUTION AND DISPERSAL OF THE PERMIAN FUSULINID GENERA PSEUDOSCHW AGERINA AND PARASCHW AGERINA

Abstract

The protozoan superfamily Fusulinacea M6ller (1878) includes a great number of marine species, most of which evolved rapidly and flourished extensively during the Pennsylvanian and Permian Periods of geologic time. This superfamily of the Foraminifera became extinct near the end of Permian time, but its geologic and geographic occurrences are known in considerable detail because paleontologists and stratigraphers have studied the diverse evolution and nearly world-wide distribu-. tion of many genera and species in order to establish age relations between fusulinidbearing strata. The two genera Pseudosckwagerina and Paraschwager,ina considered in this paper are conspicuous forms having coiled calcareous tests about 15 mm long (fig. 1). These genera first appeared near the beginning of Permian (Wolfcampian) time and became extinct before late Permian time. Pseudoschwagerina and Parasclwagerina, like the remainder of the fusulinids, are found only in rocks that are considered to have been deposited in shallow seas. These two genera occur most commonly in or near small patch reefs or bioherms where they are associated with flora and fauna of algal, brachiopod, bryozoan, and crinoid fragments that probably represent a photic zone assemblage. Thompson (1948), Miklukho-Maklai, Rauser-Chernoussova, and Rozovskaya (1958) suggested phylogenies of the fusulinid genera, and F. Kahler (1939) briefly studied the faunal succession of Pseudoschwagerina and Paraschwagerina in various geographic regions. Considerably more data are now available concerning Pseudoschwagerina and Paraschwagerina, and it is the purpose here to summarize these data and to suggest a possible phylogeny and dispersal pattern for the species placed in these two rapidly evolving genera.