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558-million-year-old Dickinsonia are identified as world’s oldest animals

Alessandra Kelley

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Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals

Confirming the identity of early animals

The first complex organisms emerged during the Ediacaran period, around 600 million years ago. The taxonomic affiliation of many of these organisms has been difficult to discern. Fossils of Dickinsonia, bilaterally symmetrical oval organisms, have been particularly difficult to classify. Bobrovskiy et al. conducted an analysis using lipid biomarkers obtained from Dickinsonia fossils and found that the fossils contained almost exclusively cholesteroids, a marker found only in animals (see the Perspective by Summons and Erwin). Thus, Dickinsonia were basal animals. This supports the idea that the Ediacaran biota may have been a precursor to the explosion of animal forms later observed in the Cambrian, about 500 million years ago.

This is very cool! And solves a mystery that has been argued about for 75 years. The Ediacran Biota is stonking weird and predates the Cambrian Explosion. Dickinsonia looked like a flat oval with striations and no one knew if it was animal, plant, fungus or what.
 

Chris P

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Way cool indeed!

Stephen J Gould's book Wonderful Life covers much of what was known as of the early 1990s about Ediacaran life. It's a good introduction if you can stomach Gould's smug biases and strawmen.
 

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This has been surmised for a long time, but it's nice to see they can use such sophisticated means for confirming it. But Dickinsonia didn't exist all by itself in the Ediacaran fauna. There were numerous other species of metazoans, all pretty strange by more modern standards, all soft-bodied. Hard skeletal parts came along shortly after, at the beginning of Cambrian time, which is based on the appearance of such. The preservation of such fragile creatures at Ediacara is rare and remarkable, but the strong suspicion is that there was a pretty varied metazoan biota present well before Cambrian time allowed the preservation of those hard skeletal remains. Ediacara is the most famous locality where such things have been seen, but I think there have been similar findings in at least a couple of other places.

caw
 

Helix

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If you're in Australia, head out to the South Australian Museum in Adelaide, where you can see (and touch) slabs of rock containing impressions of the Ediacaran fauna. The fauna is diverse. Heck, even Dickinsonia is diverse. The biggest species on display is D. rex. it's the size of a door mat!

And after visiting the museum, drive to the Flinders Ranges, where you can see Ediacara fossils in situ. And if you know where to look, you can visit the location where the Ediacaran period officially starts. It's the boundary between the glacial tillites of what's thought to be the Snowball Earth phase and the metamorphosed sandstones that bear the Ediacaran fauna.

(I'm all over this, because I did the trip in July.)
 

Alessandra Kelley

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If you're in Australia, head out to the South Australian Museum in Adelaide, where you can see (and touch) slabs of rock containing impressions of the Ediacaran fauna. The fauna is diverse. Heck, even Dickinsonia is diverse. The biggest species on display is D. rex. it's the size of a door mat!

And after visiting the museum, drive to the Flinders Ranges, where you can see Ediacara fossils in situ. And if you know where to look, you can visit the location where the Ediacaran period officially starts. It's the boundary between the glacial tillites of what's thought to be the Snowball Earth phase and the metamorphosed sandstones that bear the Ediacaran fauna.

(I'm all over this, because I did the trip in July.)

Ooh, lucky!

Snowball Earth is such a fascinating phenomenon. I want to make a big cartoon explaining it, and what came out of it. The Ediacran Biota (I guess they can call it Fauna now, or at least some of it) is weird and interesting. It’s neat how such ridiculously fragile lifeforms could fossilize so cleanly.
 

Helix

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Do the cartoon!!!

The biochemical evidence is brilliant.

Among the fossils are tracks and feeding trails, and some of the fossils, such as Kimberella, have an orientation (with an anterior and a posterior) and bilateral symmetry, so those have been considered to be animals for quite a time. But what sort of animals*?

*Probably a protomollusc in the case of Kimberella**

**And some of the others might be cnidarians***

***But there are some really, really weird things all right.
 

MaeZe

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That's fantastic! I so want to go back to Oz.

Did I tell you I have a couple dinosaur bones from a hadrosaur that, believe it or not, I found in a box of rocks at a yard sale? Kids were selling grandpa's things, didn't know what they had. I didn't either until I took them to the U of WA's, Burke museum's 'Artifact Day'.

The professor was excited enough to take us downstairs to the back rooms so he could look at them under a microscope. What I thought might be part of a spine was actually a foot bone like a metatarsal. One of the bones was part of a jaw, with teeth.

Hadrosaurs are also called duck-billed dinos but they don't have bills, they have teeth. They are plant eaters. I also thought they were from Alberta, Canada because there are some fossil fields there. But they were probably from around the Badlands of North Dakota.

Still, nothing compared to the natural wonders in Australia.
 

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What a cool find, MaeZe. How exciting!

If you return to Oz, make sure you head up to Winton, Hughenden and Richmond (western Qld) a.k.a. the Dinosaur Triangle. Australia doesn't have a huge variety of dinosaurs compared with the other continents, but there have been some interesting discoveries, including titanosaurs, ankylosaurs and some 'raptors'. Oz does have a good selection of Cretaceous marine reptiles from the Eromanga Sea (western Qld). The skeleton of the terrifying Kronosaurus (on display at the MCZ) was excavated from Hughenden in the 1930s.
 

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As an aside, there is a really good four-program set of documentaries about the geology of Australia, titled "Australia's First Four Billion Years." I use the first episode, and occasionally another one, in my intro geology classes at the local university It is narrated, wonderfully, by an Oz biologist named Richard Smith, and the production values are fantastic. In the first episode, he visits the original Ediacara fauna discovery site, among many other fascinating places. Worth a look.

caw
 

frimble3

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At a rate of one billion years an hour? That must an impressive show of editing! The world in fast-forward?