Ars Technica is reporting on a paper published on 7 July 2022 in the journal Science, where researchers believe they've identified one of the first vertebrates.
From the article:
A group of organisms called yunnanozoans had gills, precursor to jaws.
Because we're a member of the group, it's easy to see vertebrates as the pinnacle of evolution, a group capable of producing bats, birds, and giant whales in addition to ourselves. But when they first evolved, vertebrates were anything but a sure thing. They branched off from a group that lived in the mud and didn't need to tell its top from its bottom or its left from its right, and so ended up losing an organized nerve cord. Our closest non-vertebrate relatives re-established a nerve cord (on the wrong side of the body, naturally) but couldn't be bothered with niceties like a skeleton.
How exactly vertebrates came out of this hasn't been clear, and the probable lack of a skeleton in our immediate ancestors has helped ensure that we don't have a lot of fossils to help clarify matters.
But in Thursday's issue of Science, researchers have re-evaluated some enigmatic fossils that date back to the Cambrian period and settled several arguments about exactly what features the yunnanozoans had. The answers include cartilaginous structures that supported gills and a possible ancestor to what became our lower jaw. In the process, they show that yunnanozoans are likely the earliest branch of the vertebrate tree.
[...]
You can get a sense of what a yunnanozoan looks like from the image above. The soft tissue down its flanks was divided into segments, a feature in both our closest living non-vertebrate relatives (the amphioxus or lancelet) and is present in vertebrate embryos but generally gets lost as they proceed through development into adults. Near the animal's head—and it does have a clear head and mouth—there's also an array of arched structures that look a lot like the similarly located gill arches found near the head of modern fish.
Journal Reference:
Qingyi Tian, Fangchen Zhao, Han Zeng, et al., Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans, Science, 377, 6602, 2022. DOI: 10.1126/science.abm2708
(Score: 3, Informative) by tangomargarine on Thursday July 14 2022, @05:03PM (2 children)
"They think that gills *evolved into* jaws? I have a hard time believing that..."
The gills and the precursor to jaws are two different things, not the latter an appositive for the former.
I see that our schools are continuing to do an excellent job of training people for a career in journalism.
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 3, Informative) by NotSanguine on Thursday July 14 2022, @07:26PM
I can't agree.
While the sentence:
is a little awkward, it certainly can be read as:
"A group of organisms called yunnanozoans had gills as well as a precursor to jaws."
Which TFA makes perfectly clear that's what they mean.
The bolded sentence is a sub-heading after the headline which provides a brief summary. That's pretty common journalistic practice for such sub-headings.
Feel free to disagree, and if you don't like John Timmer's prose in Ars Technica, then just read the paper.
That said, I found it fascinating that researchers were able to identify gill-like structures and jaw precursors (made of cartilage, not bone) from 400+ million year old fossils.
No, no, you're not thinking; you're just being logical. --Niels Bohr
(Score: 3, Informative) by Immerman on Thursday July 14 2022, @07:39PM
I think you're just misreading that. Try parsing it the same way you would:
It's a pretty common phrasing. It's not like they said:
which would be required for a grammatically correct expression of your interpretation, and would be legitimately ambiguous.
(Score: 1, Interesting) by Anonymous Coward on Friday July 15 2022, @02:28PM
https://en.wikipedia.org/wiki/The_Ancestor%27s_Tale [wikipedia.org] (by Richard Dawkins and Yan Wong)
There's a discussion there about the earliest vertrebates (as well as most other "interesting" ancestors of humans, from an evolution perspective).
I mentioned the book also because the summary talks about "nerve cord on the wrong side of the body". Dawkins and Wong actually talk about the fact that, most likely, nerve cords first appeared on the "down" side of the body, then one of our ancestors turned its head by 180 degrees, and so we now have it on the "up" side of the body. Furthermore, they provide examples of fish that are doing the reverse now (and actually there is a species of fish that has turned "upside down" completely). I *believe* it's this thing http://animaladay.blogspot.com/2014/02/blotched-upside-down-catfish.html [blogspot.com] (most importantly, the dark color is on "belly" rather than "vertebrae side", so there is active selection for swimming with vertebrae "down"); I may be wrong and the book may have a better example, I don't have it on hand here.
Notably, Terry Pratchett and friends, in one of their "science of discworld" volumes, say that this turning of the head by 180 degrees is probably responsible for breathing tube intersecting our feeding tube, which anatomic peculiarity is fascinating because it introduces the possiblity of choking, which sounds like a big argument against survivability...