CONICET | Buscador de Institutos y Recursos Humanos

The affinity and paleoecology of the body fossils of the terminal Ediacaran has been highly debated since the last century. Previous discoveries of late Ediacaran fossils in South America are restricted to biomineralized remains of the Nama Assemblage assigned to shelled metazoans, as Cloudina and Corumbella. Apart of some dubious occurrences in Brazil, there is no definitive record of Ediacaran body fossils recorded so far in South America. In this contribution, we firstly report the existence of hundreds of specimens identified as holdfasts structures of Aspidella terranovica Billings in the Cerro Negro Formation, Grupo La Providencia, Argentina. These discoidal fossils occur as positive epirelief associated with microbially induced sedimentary structures and sparse ichnofossils. The Fossils are preserved in fine grained sandstones interpreted as deposited in shallow-water conditions under tidal influence. Morphologic and taphonomic features suggest the ?Flinders-style? of preservation, typical of Ediacaran representatives found in Australia. The large number of individuals and the notable differences in size suggest that South American Aspidella lived in high-density assemblages, probably characterized by high rate of young individuals, with no size-selection during the mortality event, an episode of rapid sedimentation which caused community to smother. The presence of Aspidella in the Cerro Negro Formation, Argentina, places the unit in the latest Ediacaran, as reinforced by the presence of trace fossils. The new finding epitomizes the definitive record of Ediacaran soft-bodied fossils in South America and supports the cosmopolitan paleobiogeographic distribution of Aspidella. It also supports recently proposed scenario of the Clymene Ocean - a shallow sea covering most part of southeast Gondwana at the end of the Ediacaran.