Soft-bodied macroscopic fossils have long been known from upper Neoproterozoic (Ediacaran) rocks, but they continue to generate much excitement among geologists. Biologic interpretations of Ediacaran organisms have been all over the map. Many Ediacaran fossils appear to be animals, but some paleontologists have interpreted them as lichens or giant protists or members of an extinct kingdom.
One of the quintessential examples of an Ediacaran fossil is Dickinsonia. Prima facie, it appears bilaterally symmetrical, but it does have subtle asymmetry. It has the general appearance of a flattened worm with a stretched pancake body. These Dickinsonia specimens are from the Flinders Ranges of South Australia, one of the world’s classic localities for Ediacaran fossils. As do most Ediacarans, these Dickinsonia display soft-part preservation in a matrix of clean, quartzose sandstone.
Dickinsonia costata (~7.7 cm long), SAM P13750/P40679 (South Australian Museum, Adelaide, Australia)
Dickinsonia costata (~7.2 cm long), SAM P41125 (South Australian Museum, Adelaide, Australia)
Dickinsonia costata (centimeter scale), YPM 35467 (Yale University's Peabody Museum, New Haven, Connecticut, USA)