The return of the giant lichens?

Gosh, can someone tell me if this is bullshit or if he has a point? O.o

It’s rather annoying when a paper comes out that basically threatens to turn what you think you know on its head, and you’re simply not equipped to evaluate its claims. This is the case with Retallack (2012). I’m fascinated by early animals, and endlessly bewildered by the strange fossils of the late Precambrian. While I’m aware that Ediacaran fossils have been interpreted as everything from microbial mats through animals to giant protists, I had the impression that the non-animal interpretations of iconic fossils like Dickinsonia, Spriggina, Parvancorina or Charniodiscus have slowly retreated to the fringe in the decades since their discovery.

And now this guy, whose name I’ve heard enough times to pay attention, gets into Nature arguing that the namesake formation of the Ediacaran period actually originated on dry land, and the iconic fossils are preserved in a manner more like plants, fungi or lichens than animals.

The paltry one semester of introductory geoscience I did years ago is nowhere near enough to comment on all the stuff he says about soils and microbial mats and preservation. I feel completely out of my depth, rocking precariously at the mercy of the waves…

Obviously, this assessment of the original Ediacara site doesn’t affect every fossil site from the period. The latest Precambrian reefs of the Nama Group remain marine reefs containing the remains of unknown animals that grew some of the first mineralised skeletons.

My big question at the moment is how Retallack would interpret the preservation of the White Sea assemblage. This contains similar kinds of fossils to the sites he’s reinterpreted as terrestrial. There’s Dickinsonia and several others like it, there’s Parvancorina, there’s Cyclomedusa*. And this is where hundreds of specimens of my Platonic love Kimberella come from, often associated with crawling and feeding traces. That guy moved around and grazed – plants and lichens seldom do such things! So was Kimberella a land animal? That would be the biggest palaeontological sensation of the decade if not the century. Or did dickinsoniids etc. occur both on land and underwater? Or did the White Sea fossils span a wide variety of environments? (I’m not sure about the distribution of the various White Sea fossils relative to each other…)

Oh my. I wonder what will come out of this. Publication in Nature makes it dead certain that any expert who’d vehemently disagree will find the article. Let’s pull out the pop corn and watch…

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*It’s slightly odd that he seemingly treats Cyclomedusa and other “medusoid” fossils as though most people considered them jellyfish. That may have been their original interpretation, but I thought it was widely discredited now.

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Reference:Retallack GJ (2012) Ediacaran life on land. Nature advance online publication available 12/12/12, doi:10.1038/nature11777

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