Ancient worm fossil rolls back origins of animal life

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#1

https://www.nature.com/articles/d41586-019-02556-x

The fossil, which formed some time between 551 million and 539 million years ago, in the Ediacaran period, joins a growing body of evidence that challenges the idea that animal life on Earth burst onto the scene in an event known as the Cambrian explosion, which began about 539 million years ago.

“It is just pushing things further and further back into the Ediacaran,” says Rachel Wood, a geoscientist at the University of Edinburgh, UK. The Cambrian explosion no longer appears to be such an abrupt event in the history of life on Earth, she says.

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#2

Man, those paleontologists and geologists must have sharp eyes, I probably would’ve just chucked it across a pond. :wink:

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#3

Yet another lengthening of the increasingly ill-named Cambrian Explosion. :exploding_head:

A YEC once tried to pin me down on the sudden appearance of trilobites, but a quick Google showed multiple more recent discoveries pushing the evolution of trilobites back by … a lot … 60 million years comes to mind, but no time to fact-check just now…

#4

I’m unaware of that and also dubious. Could you try that Google again?

Note: I tried Google, and I couldn’t find anything older than Cambrian Stage 3, the base of which is actually defined by the earliest appearance of trilobites, at 521ma. Clearly, though, this is a taphonomic artifact and presumably represents the evolution of a calcified exoskeleton in a previous existing but unpreserved arthropod that already looked like a trilobite.

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#5

I can Google the recent discoveries, but not the claim I was debunking.

Memory jogged! The claim was about the miraculous appearance of life during the Cambrian Explosion, with the example of trilobites with fully formed nervous system, and no precursor fossils. Maybe this or some similar discovery:

The assumption that amongst internal organs of early arthropods only the digestive system withstands fossilization is challenged by the identification of brain and ganglia in early Cambrian fuxianhuiids and megacheirans from southwest China. Here we document in the 520-million-year-old Chengjiang arthropod Fuxianhuia protensa an exceptionally preserved bilaterally symmetrical organ system corresponding to the vascular system of extantarthropods
https://www.nature.com/articles/ncomms4560.pdf?origin=ppub

I was able to find new discoveries of older fossils, several since 2013, though not so well preserved. Goalpost were quickly moved! :wink:

I agree 60M wrong, but there are some fossils indicating the CE may be much longer than originally thought, and what might be where 60M popped into my head. Sorry for my confusion.

#6

That’s what I was asking about.

Yes, that’s what I’m asking about. Did you find trilobites older than the base of Cambrian Stage 3 (or the based of the Atdabanian, or 521ma)?

This raises the question of what “Cambrian explosion” means and what would signal its beginning. I would claim that the traditional start of the explosion, at the aforementioned 521ma, is a double taphonomic artifact: the coincidence in time of mineralization in trilobites with the proper conditions for Burgess-type preservation in several localities. By the time we can get a good view of the explosion, most of it is over. We are left with tantalizing clues: the small, shelly fauna and the ichnofossil record. I don’t think anything has extended that in time.

#7

To paraphrase Dr. McCoy …

Dammit Jim, I’m a statistician not a paleontologist! :t_rex:

:slight_smile:

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#8

/argument/artifact/

#9

Being unsure of my own reference, I can only say the age of the oldest known trilobite fossil had been pushed back by millions of years. A current casual search turns up the oldest as ~540ma.

#10

According to what source?

#11

The first hit today is Wiki. Not a great source, I know, but I can’t reconstruct my entire pattern of thought+search for you.

Here is another claiming 540ma:
https://ucmp.berkeley.edu/arthropoda/trilobita/trilobitafr.html

#12

Based on my casual search, I think the older dates are spurious, as they refer to the same trilobites found at the base of Cambrian Stage 3.

That would appear to be based on some very outdated dates for the start of Cambrian Stage 3 (and also for the end of the Cambrian, which is now 488ma, not 500ma), which was once also considered the start of the Cambrian. Now in fact, the Cambrian now starts at 542ma, and most of the Early Cambrian happens before the known appearance of trilobites, again at 521ma.

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#13

OK guys, I’ll cry UNCLE. I was recounting how I was to refute a bad claim with better information, and now it seems the whole thing has shifted out from under me. My information may be out of date, but I’m not trying to lie to you.

#14

Won’t work with out the s & p.

#15

Did you just make a sed joke?

#16

I miss stuff and walk over stuff all the time. Then the guy behind me will find it. My mentor has amazing eyes. He will see the sun glistening off something