Introduction

On the following plates are illustrated microfossils from 48 geologic units (representing about 10% of the units listed in Table 22.3). Although coverage is by no means exhaustive, the fossils illustrated are representative of the diversity and level of organization exhibited by particularly well-preserved Proterozoic assemblages. In selecting the fossils illustrated, emphasis has been placed on inclusion of holotype specimens, particularly holotypes of taxa described from the Soviet Union, relatively few of which have been previously illustrated in the non-Russian language literature (and none of which has been previously illustrated using interference contrast optics). As summarized below, emphasis has also been placed on illustration of assemblages of Middle and Late Proterozoic age; this atlas therefore complements, but does not duplicate, illustrations of Early Proterozoic communities included in Hofmann and Schopf (1983). The atlas contains more than 300 new illustrations, including photomicrographs of specimens not previously figured from the Dismal Lakes Group, River Wakefield Subgroup, Skillogalee Dolomite, the Gunflint Iron Formation, and the Gaoyuzhuang, Galeros, Kwagunt, and Myrtle Springs Formations.

Acknowledgments

Soviet type specimens were provided for study by E. Aseeva, T. N. Hermann, T. Jankauskas, N. Mikhailova, V. Sergeev, and A. Weiss; photomicrography of these specimens was carried out by C. V. Mendelson, J. W. Schopf, and G. Vidal; this work, conducted at the Palaeontological Institute in Moscow, was facilitated through the courtesy of M. A. Fedonkin and B. S. Sokolov. Studies of new material from the Gaoyuzhuang Formation were carried out in collaboration with R. Mikawa (University of Chicago); studies of new specimens from the River Wakefield Subgroup and the Skillogalee Dolomite were carried out by or in collaboration with T. R. Fairchild (Universidade de Sao Paulo, Brazil).