Ediacaran microbial colonies
Version of Record online: 15 JUN 2007
Volume 40, Issue 3, pages 201–210, September 2007
How to Cite
GRAZHDANKIN, D. and GERDES, G. (2007), Ediacaran microbial colonies. Lethaia, 40: 201–210. doi: 10.1111/j.1502-3931.2007.00025.x
- Issue online: 15 JUN 2007
- Version of Record online: 15 JUN 2007
- Manuscript received on 21/01/07; manuscript accepted on 28/04/07.
- Ediacaran fossils;
- Flinders Ranges;
- White Sea;
Enigmatic discoidal fossils are common in Neoproterozoic sedimentary sequences and in the stratigraphic record pre-date the first appearance of diverse Ediacaran fossil assemblages. Termed ‘medusoids’, these Neoproterozoic discoidal fossils have generally been interpreted as coelenterate-grade organisms implying a radially symmetrical body plan for ancestral eumetazoans. Analysis of exceptionally preserved discoidal fossils from the White Sea area, however, indicates that most of these discoidal forms represent colonial microbes. Localized pyritization, for example, reveals the presence of a conspicuous filamentous substructure in Ediacaria, whereas concentric rings, radial sectors and central structures in Cyclomedusa and Paliella compare directly with Recent microbial colonies growing in a nutritionally heterogeneous environment. At least some Ediacaran discoids can be compared with extant concentric ring-shaped microbial colonies that grow in hypersaline microbial mats. Insofar as most of the remaining record of Ediacaran discoids can be attributed to the holdfast structures of non-radiate modular organisms, there is no support from the fossil record for identifying a radiate ancestry for the Metazoa.