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Adam Maloof - Research

Digital Fossil Reconstruction

While studying the evolution of pre-, syn-, and post-glacial environments associated with the Marinoan (~640 Ma) ice age in South Australia, our group puzzled over strange red cm-sized flecks and blobs (see cover image below) frequently found within stromatolite flake breccias of the Trezona Formation (just stratigraphically below the glacial deposits).  We tried to convince ourselves that the red shapes were just mud chips, but eventually the constant recurrence of rings, anvils, wishbones and perforated blobs made us suspect a biological origin.  Because these organisms would be large, complex, and older than the younger of two snowball Earth episodes that punctuated the Cryogenian Period, we were particularly eager to figure out what these fossils might be.

However, because the red fossils are essentially identical in density and solubility to the matrix around them, they were impossible to image with x-rays or extract with acid-dissolutions.  All we had to work with was the color contrast.  So first, we selected a sample, cut it into a slab, and used a precision grinder to remove 50 microns at a time from one side (the same kind of serial grinding routine employed by Wes Watters and John Grotzinger to reconstruct Namacalathus fossils from 550 Ma limestones from Namibia).  After each pass with the grinder, we photographed the surface, so that we ended up with nearly 500 precisely aligned photographs separated by 50 microns in the z-direction (see figure below). Next, we embarked on a collaboration with Situ Studio to develop software to autotrace objects of interest based entirely on the color-contrast of the red fossils, without human bias.  The result was a stack of 500 polygons representing the outlines of individual fossil specimen.  Then we modeled these contours as a volume that we could interpret in terms of functional morphology, in the context of the evolutionary tree of life.  We interpreted the fossils as sponge-grade metazoa with an internal water canal network. Animal-grade organisms before the snowball Earth!

ngeocover

Please find a link to our paper here [pdf], and have a look at some of the media related to this work:

[BBC World Service] [Nature Geoscience] [News & Views] [Princeton] [Science] [NSF] [Philadelphia Inquirer] [Trenton Times] [New York Times T] [New York Times] [New Scientist] [Discovery] [LiveScience] [ScienceNews] [The Guardian] [Daily Mail] [BBC Radio4] [Situ Studio] [CBS] [Highly Allochtonous] [Slashdot] [Wired] [Discover] [Astrobiology] [Australia] [Deutschlandfunk] [ScineXX]

Currently we are working together with Situ Studio to build an automated serial grinder/imager for digital fossil reconstruction that will be significantly more precise and efficient than currently available technologies.