RUGOSOOPSIS: A NEW GROUP OF UPPER RIPHEAN ANIMALS

Abstract

The Upper Riphean Lakhanda biota (from the Uchur-Mayai region of SE Siberia) contains abundant, well preserved and highly biodiverse microfossil assemblages including Rugosoopsis microfossils, characterized by a uniform shape, with prominent closely transversely spaced wrinkles on the outer surface. Rugosoopsis are the oldest, microscopic vermiform organisms, with a typical morphology of closely spaced wrinkles on the body's outer surface resembling the Late Vendian-Early Cambrian Sabellidites, and even more the smallest representatives in the genus Sokolovina Kirjanov, 1968 (Sokolov 1997). Different types of Rugosoopsis preservation can be explained by the presence of numerous bacterial microorganisms on the body of Rugosoopsis and on organic films. Rugosoopsis organisms inhabited the bottom, where they likely existed alongside saprophytic microbes in finely dispersed organic debris. The community of Rugosoopsis and bacteria appears to represent a stable trophic system. The exceptional preservation of these microfossils is due to the favourable sedimentary environment in the Lakhanda Basin.