Fossil Organisms of the Kotlin Regional Stage of the Upper Vendian of the Northwestern Russian Platform (Leningrad Region)

The environments of the Upper Vendian microscopic and macroscopic fossil organisms of the northwestern Russian Platform were reconstructed, and vertical distribution was analyzed. Five assemblages of the Kotlin age were determined: one impoverished transit assemblage and four abundant ones. A monographic restudy of the following filamentous algae was carried out: Aataenia reticularis Gnilovskaya emend. and Bicuspidata fusiformis Assejeva, emend. The latter was compared to cyanobacteria of the order Oscillatoriales. A new acritarch species Pterospermopsimorpha rigida sp. nov. was described.