shakeup for the tree of life

monty

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There's a paper in Nature this week that is full of interesting stuff, including several curve-balls, resulting from a very comprehensive molecular evaluation of relationships between animal groups.

On topic first: molluscs are monophyletic.

Now that I got that out of the way, the non-ceph but most astounding part: Ctenophores (comb jellies) are a separate group from the rest of the metazoans, including sponges. So the metazoa/eumetazoa split is wrong.

In other words, we're more closely related to sponges than to comb jellies. In fact, jellyfish are more closely related to us and sponges than they are to comb jellies.

The article also resolves controversies and validates morphological taxons to some extent: Protostomia, Ecdysozoa, and Lophotrochozoa come out winners, spiral cleavage not so much (in terms of clades, anyway). And the coin "clade A," "clade B," and "clade C" where "clade C" contains our friends the molluscs and clade B, which is a bunch of worms and brachiopods and stuff. Clade C is all the animals that have or whose ancestors had shell-like bits of a certain sort, including mollusc shells. Read the paper if you know/care about these details, 'cause I'm not really qualified to discuss 'chitinous chaetae.' Also, some juggling of the arthropods is described (sorry, Roy, no stomatopods).

The abstract is at

http://www.nature.com/nature/journal/v452/n7188/abs/nature06614.html

and if you have institutional access, the PDF is at

http://www.nature.com/nature/journal/v452/n7188/pdf/nature06614.pdf

There's a mainstream science press article that's got some horrible misrepresentation in it here:

http://www.livescience.com/animals/080410-first-animal.html

but while reading that one, keep in mind that their use of "first animal" is horrible misleading... what they really mean is "last common ancestor between comb jellies and other animals," which was certainly not anywhere close to a "first animal," and shared common traits between apes, octopuses, sponges, and comb jellies, so may not have looked any more like a comb jelly than like an ostrich. Anyway, there were certainly many ancestors leading up to that last common ancestor, and we even know a little about what some (the Edicarian fauna) looked like... like these, for example:

http://www.reuters.com/article/scienceNews/idUSN2040405820080320?sp=true
 
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I just finished my exam for invertebrate zoology, and in it we learned all of what you are saying has changed. As upsetting as it may seem to have my knowledge of inverts be based on false assumptions, I think it's really cool how they can use molecular evidence to sort it out.
 

Steve O'Shea

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..... Heather, what we were taught years ago differs from what you were taught, and from that presented in this Nature article.

There never is a 'last word' in phylogenetic matters. Believe me, this will all change again. If we were to uncritically accept everything that was published, even in Nature, we'd go ever-so-slightly insane.
 

monty

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Yeah, this is a sign that you're not in a boring, stagnant, stodgy field. But rather a wet, squishy, and slimy one. Er, as well as a vibrant, growing, exciting one!

Plus, you probably didn't have to look up the Latin names for water bears and velvet worms and such like I did...
 

monty

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Tintenfisch;115058 said:
Cool about the velvet worms being a sister-group to arthropods! I'll have to see if I can get hold of this.

I suspect Hallucigenia would have preferred to be a sister to cephalopods, but so it goes. The water bears being so far separate is interesting as well.
 
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Steve O'Shea;114969 said:
..... Heather, what we were taught years ago differs from what you were taught, and from that presented in this Nature article.

There never is a 'last word' in phylogenetic matters. Believe me, this will all change again. If we were to uncritically accept everything that was published, even in Nature, we'd go ever-so-slightly insane.

On the last day my professor told us not to look at our notes 20 years from now expecting them to still be valid because things would have changed by then. I just didn't expect this to happen so soon. Really all it means is that there is always going to be a lot of opportunities in science, which is nice.
 

Octodude

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You know, I was about to leave for class, it got cancelled, I came on here and stumbled across this, and am a much happier person. This great reading I have to say, thanks for posting.
 

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