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Discovery of the oldest trace fossils?

on . Posted in General Ichnology

EdiacaraAlexLiu

One of our own, Alex Liu, has hit the headlines this week with the publication of his discovery of trace fossils in the Mistaken Point Formation at Mistaken Point itself (which is near Cape Race, Portugal Cove South, on the southern tip of the Avalon Peninsula, about 2.5 hrs drive from MUN).  Alex has a real eye for discovering fossils, which-when combined with his dedication to fieldwork-has led him to unearth new finds from localities thoughout the Avalon and Bonavista areas in localities that have been considered to be "done to death".

Alex made the discovery in the summer of 2008 while he was a visiting student with us at MUN (he is co-supervised by Martin Brasier at Oxford University and myself). 

My first knowledge of the material came from an excited but cautious e-mail from Alex send via the dodgy internet connection at Trepassey.  Alex sent an e-mail with photos attached for comment, I think he knew that they were trace fossils even then.  We had the normal to-ing and fro-ing between co-authors as we sought to exclude all abiogenic possibilities.  Alex and I sought to demonstrate that the traces were formed by an animal by studying the locomotory activity of a number of phyla in the MUN ichnology aquaria. 

The trace fossils are unusual in that they are surface trails with prominent lateral "levees" and arcuate internal ridges.  Some of the trace fossils end in a circular impression that resembles the cast of an anemone or the Ediacaran fossil Aspidella.  The only time I had seen anything similar was in my 3rd year biomechanics course at Manchester University as an undergraduate, when we studied anemone locomotion, so we decided to go and get some anemones from the local coastline (collected from under the dock at Ferryland with my youngest son Patrick) and specimens of a second species were donated by the Ocean Sciences Centre at MUN, and see what happens when you put them on a soft substrate (the local species are naturally hard-bottom dwellers).  Sure enough, they were unhappy enough with being on mud such that they started wandering around on the floor of the tank producing surface trails with prominent lateral "levees" and arcuate internal ridges!

So we had, to our satisfaction, demonstrated that a biological mechanism was possible if not even probable.  We now consider that the Ediacara did indeed include mobile animals as well as the sessile Ediacarans.  The big question is.... what role did they have in the Ediacaran ecosystems?

We have been asked, how come such things have not been seen before.  I would suggest that the trace makers are possibly  just a rare component of the fauna, or perhaps they just did not choose to wander around very much.

There are still lots of questions to be addressed, just get out there and let the rocks tell you their stories.

 

See:

http://www.newscientist.com/article/dn18479-found-the-first-ever-animal-trails.html

http://geology.gsapubs.org (February 2010)