Erratum


Today, I was reading the headlines on LiveScience and came across this article on the Sea Urchin genome. It's interesting to me because the HGSC at Baylor did most of the work. George Weinstock, the fellow quoted in the article - he's two offices down from me. (Note that this doesn't mean he has any idea who this lowly graduate student is...)

Anyway, about halfway through the article, I noticed a sentence that said that sea urchin research would be useful, because they are the first chordate to be sequenced.

Say What?!

Here's a quick lesson in the relevant taxonomy (don't let your eyes glaze over - this is interesting stuff!) Chordates are members of the phylum Chordata. Phyla are large taxonomic groups (remember the acronym?) and Chordata includes all vertebrates, along with just a few invertebrates. I'm almost positive that Homo sapiens was the first Chordate to be sequenced. It wasn't until after the human genome that we moved on to other mammals and more far-flung creatures like the Sea Urchin.

That's not even the worst part_ Sea Urchins are actually members of the phylum Echinodermata, which means they aren't chordates at all! Their phylum includes species like starfish and sea cucumbers.

I let the folks at LiveScience know through their contact form, and to their credit, they re-checked their facts and made some changes to the article. The section now reads_

They belong to the phylum Echinodermata, which includes starfish and sea cucumbers, whereas humans belong to the phylum Chordata, or all animals with backbones. Both the echinoderms and chordates belong to a larger group called the deuterostomes.

This relationship means sea urchins can serve as a model for understanding how the group of animals that includes humans split off and evolved different traits.

Kudos for them for being quick to respond.

Update: As RPM points out in the comments, they're still wrong. The offending passage_

humans belong to the phylum Chordata, or all animals with backbones.

Chordata, as I said above includes all vertebrates and some invertebrates. They're characterized by having a dorsal nerve chord at some stage in their development. Looks like it's time for another email.

Comments

Written by RPM -

Chordates are members of the phylum Chordata - a large group fairly high up on the tree of life that includes all vertebrates, along with just a few invertebrates. I didn't know we could measure the height of taxa in a phylogeny. What algorithm do you implement for such an analysis? And they're still wrong_ humans belong to the phylum Chordata, or all animals with backbones. Chordates all have dorsal nerve chords. Vertebrates are the ones with backbones. Vertebrates are nested within the chordates.

Written by Chris -

> I didn't know we could measure the height of > taxa in a phylogeny. What algorithm do you > implement for such an analysis? You're right that I phrased that poorly. I was trying to give an idea of what a phylum was to my non-science readers. Conceptually, it's a subdivision that's higher on the tree of life than, say genus or species level splits. I rephrased it in the article to make it more clear what I was talking about. > > And they're still wrong_ > > humans belong to the phylum Chordata, or all animals with backbones. > > > Chordates all have dorsal nerve chords. Vertebrates are the ones with > backbones. Vertebrates are nested within the chordates. > Ha - you're right! I was so happy that they made the quick change that I missed the new glaring error (even though I talked about that earlier in the post!) Looks like it's time for another email...

Written by RPM -

It looks like I just misread what you wrote. I thought you were implying that chordates are "higher eukaryotes". It's a pet-peeve of mine when people do this. If you were simply saying that phylum is a broader classification than genus or species, it came out unclear.

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