The Lena River and Aldan River flow through some of the wildest country in Siberia. The rocks exposed on their banks contain an enormously rich assemblage of Lower Cambrian fossils, documenting the earliest evolutionary radiations of animals with skeletons. Fossil mollusks, trilobites, brachiopods, and a large number of millimeter-sized, problematic fossils collectively referred to as "small shelly fossils" characterize the fossils of the region.
Localities on the Aldan River have been studied intensely by both Russian and foreign researchers. UCMP professor Jere Lipps was part of an international expedition to the region in 1990.
Bergeroniellus spinosus, a redlichiid trilobite
Pagetiellus sp., an eodiscid trilobite