STRANDED AND STRETCHED IN THE EDIACARA MEMBER (RAWNSLEY QUARTZITE, SOUTH AUSTRALIA): PRESERVATION OF THE TAPHONOMICALLY ELITE BODY FOSSIL, DICKINSONIA
Fossils on these beds, and in other localities preserving fossils of the soft-bodied Ediacara Biota, are largely interpreted to be in situ. However, recent discoveries indicate that Dickinsonia can be preserved after enduring significant biostratinomic processes. For example, a considerably “ripped” specimen of a Dickinsonia rex, over 30 cm long, is preserved in a ripple trough and draping over several ripples. The integrity of the ripples is not affected but a nearby well-preserved Dickinsonia tenuous dampened the underlying ripples and was presumably preserved in life position. Deformed and stretched Dickinsonia also occur rarely.
Dickinsonia specimens are also preserved in incomplete “roll-up” positions, along with Charniodiscus, within massive sandstones interpreted as high-energy channel fills. The fossils are interpreted to have been “caught up” in the channel sands as they were being deposited. The preservation of these transported soft-bodied animals is remarkable. While the phylogenetic association of Dickinsonia is the subject of some debate, these occurrences indicate that Dickinsonia was constructed of a relatively tough material able to hold up not only through casting by overlying sands typical of all Ediacara Member fossils but that the body of Dickinsonia had enough integrity to withstand considerable transport and high-energy events and still be intact enough for species-level identification.