Fossil Friday: Dickinsonia

by Rich Feldenberg

Welcome to the long forgotten Ediacaran Period (635-542 Million years ago) in the Precambrian.  An assortment of unusual and fascinating fossils have been found dating to this time period, when multicellular life was just getting large enough to make good fossil imprints.  It is sometimes known as "The Garden of Ediacaran" because it is thought that at this early stage of animal evolution most creatures were basically filter feeders, and no major predation had yet developed (including the tools used by predators such as teeth, eyes, or sophisticated brains).  In that sense it may have been a very peaceful and "innocent" chapter in the history of life, before an evolutionary arms race between predator and prey began in the Cambrian and continues on to this day.

One common fossil found in rocks of this age is that of Dickinsonia.  This little guy was round shaped with a bilateral symmetry - something that shows some level of sophistication from the even earlier radially symmetric ancestors.  It seems to have had a head-end and a tail-end and was divided into segments.  It is not clear what kind of animal Dickinsonia really was, and there is a great bit of controversy in the scientific community in regards to its proper placement on the tree of life.  It seems to have been capable of movement over the ocean floor, as there have been fossilized tracts found that are thought due to its movements.   It may have belonged to a phyla that went extinct by the end of the Ediacaran period, or alternatively it may be related to modern day creatures.  Some experts have speculated that it is related to modern day jellyfish and some even think it may be related to animals that eventually became vertebrates.  Others have even gone so far as to say that it was not an animal at all, but part of a short lived, and ultimately unsuccessful evolutionary experiment in some type of multicellular life form that went extinct half a billion years ago.  What ever Dickinsonia was it made beautiful fossils!