How dinosaur arms turned into bird wings

September 30, 2014, Public Library of Science

Although we now appreciate that birds evolved from a branch of the dinosaur family tree, a crucial adaptation for flight has continued to puzzle evolutionary biologists. During the millions of years that elapsed, wrists went from straight to bent and hyperflexible, allowing birds to fold their wings neatly against their bodies when not flying.

How this happened has been the subject of much debate, with substantial disagreement between developmental biologists, who study how the wings of develop in the growing embryo, and palaeontologists who study the bones of dinosaurs and early . A resolution to this impasse is now provided by an exciting new study publishing on September 30 in PLOS Biology.

Underlying this striking evolutionary transformation change is a halving in the number of wrist bones, but developmental biologists and palaeontologists have different names for most of them, and seldom agree on the correspondence between specific and those of their bird descendants. Indeed, each field has radically different data sources, methods, and research objectives, talking little to each other.

The critical advance made in the new study involved combining these two strands of research. Using an interdisciplinary approach, the lab run by Alexander Vargas at the University of Chile has re-examined fossils stored at several museum collections, while at the same time collecting new developmental data from seven different species of modern birds. Joao Botelho, a Brazilian student in Vargas' lab, developed a revolutionary new technique that allows him to study specific proteins in 3D embryonic skeletons. By combining these data from both fossils and embryos, the research team has made a major step forward in clarifying how the bird wrist evolved.

From early dinosaur ancestors with as many as nine , birds have only kept four during the course of evolution, but which of the original bones are they? The identity of each of these bones was debated. For instance, the late Yale professor John Ostrom famously pointed out in the 1970's that the wrists of both birds and bird-like dinosaurs possess a very similar, half-moon shaped called the semilunate, and that this bone resulted from the merging of two bones present in dinosaurs. This formed part of Ostrom's then-controversial argument that birds descended from dinosaurs. However, the failure of to confirm this raised doubts that it was the same bone, and even that birds came from dinosaurs.

Now, the new data obtained by the Vargas lab has revealed the first developmental evidence that the bird semilunate was formed by the fusion of the two dinosaur bones. They go on to show that another bone – the pisiform – was lost in bird-like dinosaurs, but then re-acquired in the early evolution of birds, probably as an adaptation for flight, where it allows transmission of force on the downstroke while restricting flexibility on the upstroke. Combined, the fossil and developmental data provide a compelling scenario for a rare case of evolutionary reversal.

The study by the Vargas lab also settled the identity of the other two bones of the bird wrist, which were commonly misidentified in both fields. This emphasizes the downsides of not integrating all data sources, and reveals a situation perhaps akin to that of astronomy and experimental physics in the pursuit of cosmology: Together, palaeontology and development can come much closer to telling the whole story of evolution – this integrative approach resolves previous disparities that have challenged the support for the dinosaur-bird link and reveals previously undetected processes, including loss of bones, fusion of bones, and re-evolution of a transiently lost bone.

Explore further: Dinosaur family tree gives fresh insight into rapid rise of birds

More information: Botelho JF, Ossa-Fuentes L, Soto-Acuña S, Smith-Paredes D, Nuñez-León D, et al. (2014) New Developmental Evidence Clarifies the Evolution of Wrist Bones in the Dinosaur–Bird Transition. PLoS Biol 12(9): e1001957. DOI: 10.1371/journal.pbio.1001957

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Sep 30, 2014
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Steve 200mph Cruiz
5 / 5 (12) Sep 30, 2014
Verkle, this adaption took place during the Triassic period, there are plenty of fossils of what they are taking about. One of the first things some dinosaurs evolved after the permian extinction was bird like features. They have similar skulls, many dinosaurs had feathers, and things like ostriches and emus not only occupy the same niche, they have almost the exact same bone structure of certain dinosaurs.

Dinosaurs never went extinct, just the famous ones did.
4.6 / 5 (10) Sep 30, 2014
@verkle - shut up adults are talking!
5 / 5 (11) Sep 30, 2014
"Evolutionists are some of the most deluded of all scientists."

Fundamentalist that think the Bible is a science text are delusional.

There, I fixed it for you verikle.
Captain Stumpy
4.6 / 5 (10) Sep 30, 2014
What an unfounded statement!
personal conjecture not based upon evidence
please show links/proof from a peer reviewed reputable source with an impact in biology/genetics that disproves the statement and the study
Where is the scientific proof of such a ridiculous statement?
did you read the study and read the evidence for yourself? i didn't think so
a renewed look found support in both data sources for a composite radiale+intermedium, which had often been simply labelled as the radiale in both fields. The evidence for a composite semilunate cartilage shows how, despite claims to the contrary, avian development contains signals that are consistent with their origin from dinosaurs, which is a well-documented fact of palaeontology.
READ IT next time before commenting and proving to the internet world you are not only ignorant and uneducated, but a stupid acolyte of a religious order which aims to suppress science and intelligence
Captain Stumpy
4.6 / 5 (10) Oct 01, 2014
There should be millions of these such fossils if it were true!
part two
There are many, but you willfully refuse to admit the evidence as well as ignore the science. also, you make a fallacious statement based upon the assumption that all deaths formed fossils
But alas! they don't exist.
Evolutionists are some of the most deluded of all scientists
Personal conjecture based upon blatant stupidity and continuing to ignore empirical evidence presented factually over links as well as other media
see also: http://www.tim-th...ils.html





3.9 / 5 (7) Oct 01, 2014
Thanks Captain, those are great posts! Amazing amount of info on that site.
Captain Stumpy
4.5 / 5 (8) Oct 01, 2014
Thanks Captain, those are great posts! Amazing amount of info on that site.
you are welcome.
I was pointed towards it by Tim Thompson as well as a few others

another good site full of technical info (regarding evolution and Lenski, specifically) is this one: http://myxo.css.m...dex.html

there is a LOT of good info there! check it out

and if you have AAAS then keep your eyes on the Science Mag posts too...

3.4 / 5 (9) Oct 01, 2014
"They go on to show that another bone – the pisiform – was lost in bird-like dinosaurs, but then re-acquired in the early evolution of birds"

Bones may stretch or shrink, but once they are gone they are gone for good. The ancestor of birds has to be an as yet undiscovered bird-like dinosaur that retained the pisiform bone.

No, dormant gene.

Chickens still have a dormant gene for teeth, but you virtually never see a chicken with teeth.

that whole "backup copy of a gene" thing making sense now?

Once you've solved a problem, if you keep a "record" of the solution, it's a lot easier to solve if you encounter it again.
1 / 5 (4) Oct 01, 2014
In response to Verkle, I believe Verkle is a creationist that expresses himself in a confrontational manner. I am also a creationist with respect for other beliefs and their right to have them. I was not created to force my beliefs upon others simply to stand in them. I enjoy science and the theories developed by the scientific community. Please let us express ourselves without getting personal or offensive.
Thank you for reading my post and I welcome your comments.
4.2 / 5 (5) Oct 01, 2014
Returners may not notice he has proved there is no 'intelligent' design
Once you've solved a problem, if you keep a "record" of the solution, it's a lot easier to solve if you encounter it again.
Your statement above is predicated upon probability, therefore no design as such as you say "..if you encounter" etc.

Just because we as yet have not discovered the probabilistic sequence that goes from amino acids to genes does not mean such a route does not exist. Computing resources applied to combinatorial evaluations of the permutations in biochem are in their infancy and even so we have proven through genetic algorithms that complexity does arise from simplicity...

Besides who would want an 'intelligent designer' that ensures all life suffers, does not last long enough to reduce the suffering in any meaningful way of all life and that all life is part of the brutality of nature ie. "Eat and be eaten" ?

Is this consistent with the loving god of verkle, moses or Returners ?
4.6 / 5 (9) Oct 01, 2014
Please let us express ourselves without getting personal or offensive.
No. Posting creationist drivel on a science site is being offensive, so expect abuse.
Argument doesn't work with fundies. Look at any thread that verkle has posted. He, likek all creationists, are not interested in learning anything, just preaching. Go away.
5 / 5 (6) Oct 02, 2014
I am also a creationist with respect for other beliefs and their right to have them.

While that is certainly commendable, you may not be aware that it is the very thing that riles rationalists.

See, you can't just say "I respect Christians, Hindus and Scientists". It is not a form of faith. Science studies the natural. Religion studies (?) the supernatural. There is *by definition* no intersection of interest.
1 / 5 (2) Oct 02, 2014
You can say or believe whatever you want as you have that right.

Historically and today we have many scientists of faith. We would not have advanced to this point if these great minds did not have passion.

Verkle I'm not sure why evolutionary theory is so upsetting to you and what your alternative is because you always seem to stir the pot and take off. Hopefully you read the following posts. Some of you science kids might appreciate them as well.

5 / 5 (5) Oct 02, 2014
"And sometimes, one side crosses a boundary in its claims. For example, when religious tenets make strong claims about the natural world (e.g., claiming that the world was created in six days, as some literal interpretations of the Bible might require), faith and science can find themselves in conflict."

That quote from your first link is why verkle runs away.
4 / 5 (4) Oct 03, 2014
Well, I thought you guys were being harsh but in review of some of his nonsense I have altered my opinion, you could not be harsh enough.
That being said, I hold by the right of anyone to say or believe what they want even if it is lacking.
3.7 / 5 (3) Oct 04, 2014
yep maybe had too much unresolved idealism with this comment
..I hold by the right of anyone to say or believe what they want even if it is lacking.
As a general rule - I don't ie.

I don't believe the uneducated have a right to blurt idle opinion without research either in person or on forums disrupting dialectic on technical issues they don't understand & have no knowledge of. Eg. AGW deniers claiming AGW is a 'lie' when they havent achieved an education in basic physics.

I don't believe anyone should attack the character of scientists when their own argument is dismissed due to lack of rationale.

I don't believe the angry or stupid should claim people have indulged in criminal behaviour when there is no evidence or if the matter is before the courts.

I don't believe religionists should try to "convert" anyone; atheists, anti-theists or other religious devotees etc Eg trying to do this to embarrass or disrespect or ignore their rationale.

more later...
Captain Stumpy
5 / 5 (4) Oct 04, 2014
Please let us express ourselves without getting personal or offensive
Thank you for reading my post and I welcome your comments
there is a distinction between faith and science, allowing scientists (even of faith) to supersede faith during research (unless you are delusional like jvk)

This is the essence (IMHO) of NOM and animah's posts... a rational scientific process can be changed with empirical data which allows it to adapt and change over time, which makes it refine itself and become MORE correct over time (like physics, for example)

whereas the faith based belief system is stagnant and solidifies over time forcing those who believe differently to break off into factions (see xtianity) as well as competing for resources, which leads to argument and conflict (see the middle east)

It is the RIGHT of anyone to say what they believe, but it is SCIENCE to back up that with empirical evidence... which is the failing of faith
5 / 5 (5) Oct 04, 2014
That being said, I hold by the right of anyone to say or believe what they want even if it is lacking.

Fair enough, but in the appropriate forum; with rights come responsibilities. Is it OK to go into a church during every service and interrupt every sermon with interjections that the speaker is talking rubbish?
If I did that I would rightly expect to be turfed out on my ear as it is rude and disrespectful. Anyone constantly interjecting that science is WRONG and religion is "the truth" on a science forum is going to be treated the same way.
1 / 5 (1) Oct 05, 2014
Yes, I am an optimist with idealistic tendencies.

"You may say I'm a dreamer. But I'm not the only one"
3 / 5 (2) Oct 05, 2014
ref: Shitead/returners
"They go on to show that another bone – the pisiform – was lost in bird-like dinosaurs, but then re-acquired in the early evolution of birds"

Bones may ...

No, dormant gene...

developmental biology/embryology has examples of such structures created, absorbed , and repurposed . recapitulation .
1 / 5 (3) Oct 05, 2014
No. Posting creationist drivel on a science site is being offensive, so expect abuse.

science is the child of philosophy and philosophy may well be the child of religion .
abuse is unjustifiable . it's neither justice nor example .

religion and science are both filled with believers , faith , dogma , and people that don't know what their talking about . religion has its inquisition , science has its eugenics.
the difference between prediction and prophesy is connotative error in terminology and field .
1 Thessalonians 5:21 is the scientific method
1 Corinthians 13:1-13 through a glass darkly ,
and the difference between educated and wise is that wisdom doesn't flaunt it's wealth or denigrate the poor .
1 / 5 (2) Oct 05, 2014
@verkle @Mike_Massen
if there is such a thing as intelligent design , my guess is its in setting up of the dominoes.
its in the creation of the degrees of freedom that allow the emergence of the inherent properties of physics .
the illusion or reality of randomness may be , according to Heisenberg , unknowable in hindsight but that doesn't mean is was unknowable apriori.

emergent complexity is chaos theory not genetic algorithms . its a feedback process at a boundry condition ? emergent order in genetic algorithms is a result of a feedback loop implementing a cost function in place of natural selection

nature created pain , yet you would blame god for natures whip , for granting nature the degrees of freedom that life explores through evolution .
while lions seldom lie with lambs , nature appears to be evolving beyond eat or be eaten .
man has yet to evolve beyond self destruction much less make pets of all life on earth and then teach them to behave. there may be time , if not will
Captain Stumpy
5 / 5 (2) Oct 05, 2014
science is the child of philosophy
but like the mentioned evolution above, it has evolved into something far different than the faith based tenets of yesteryear. Science requires empirical evidence which allows it to continually refine knowledge to be more accurate over time, whereas the tenets of a religion solidify over time making them more rigid and divisive
Your examples are perfect to prove this: eugenics did not survive peer review and was based upon prejudice, not science, and the inquisition survives still today (albeit less bloody except in certain countries) as xtian's often persecute those who's beliefs or actions are outside the tenets of their belief (homosexuals, other religions,etc)
plus there is proof galore about the divisiveness of religion: choose ANY religion and see how many factions it has
once someone proclaims a different way to understand something, a new faction is born causing friction and prejudice
religion is only good for controlling people

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