Dickinsonia
costata
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)