Attachments of Vendian fossils: Preservation, morphology, morphotypes, and possible morphogenesis

摘要

A recent study has revealed the problematic nature of "cyclic" and "radial" fossils which represent a mixed group of organisms and are most abundant in the Vendian. As a result, the validity of dozens of genera and species has become ambiguous. The situation has emerged after descriptions of variation in fossil preservation and discovery of attachment discs which have the same morphology as "cyclic" and "radial" imprints. In this paper we attempt to describe basic morphotypes of the attachments using system-structural analysis and summarizing previously known taphonomic and morphological data. The morphotypes are arranged in a matrix table with basic lines such as "Cyclomedusa" (discs) and "Hiemalora" (rootlike offshoots). Members of mean matrix points are selected according to the basic features of the attachment discs, a possible hierarchy of these objects and the stratigraphic position of the specimens. The reconstructed pattern (morphogenetic?(?) trends) appears to be similar to that in the root system of plants (or homologous parts). Flavostratum incrustatum gen. et sp. nov., a new benthic organism with a substrate-encrusting filmlike attachment is described from the Zimnegory Formation (Upper Vendian of the Arkhangelsk Region).