Of Turtle Shells and Turtle Beaks


" Eorhynchochelys isn’t the only kind of early turtle that scientists have discovered – there is another early turtle with a partial shell but no beak. Until now, it’s been unclear how they all fit into the reptile family tree. “The origin of turtles has been an unsolved problem in paleontology for many decades,” says Rieppel. “Now with Eorhynchochelys, how turtles evolved has become a lot clearer.”

The fact that Eorhynchochelys developed a beak before other early turtles but didn’t have a shell is evidence of mosaic evolution – the idea that traits can evolve independently from each other and at a different rate, and that not every ancestral species has the same combination of these traits. Modern turtles have both shells and beaks, but the path evolution took to get there wasn’t a straight line. Instead, some turtle relatives got partial shells while others got beaks, and eventually, the genetic mutations that create these traits occurred in the same animal."

Anybody have an idea how that happens via common descent only? How did the genetic information for the shells get to the ones who only had the beaks, and vice-versa? Are they saying these traits evolved independently in several strains until the strain which made it had them all?


These are excellent questions @anon46279830. Perhaps @T.j_Runyon can comment, but I’m going to read up a bit on this specific discovery before I can comment.

@swamidass I am curious as to why you are editing the title to make the look somewhat less like the title from the original story. At other forums I have participated in they encouraged using exact wording to reduce the chance someone else posts the same article by mistake. Any guidance on that for here?

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Oh, I just do this to make it clearer at the top level where the conversation is going. Do you think we should adopt this policy?

I am possibly okay with this. However, it leaves out the reason we are bringing it up. I’m okay having an article more than once, if the discussion and focus is different each time. What do you think?

I don’t have a strong opinion on it. I do think that if the site gets much larger we will have several people posting the same article without knowing about it. I realize a side bar comes up saying “this is similar to X” but when there is a list of those it sort of undermines the point. People see the wording is somewhat different and think the article has not been posted before. I don’t think it should be a rule, just a good habit. What puzzles me is intervention going the other way- to make it less like the original title. I suppose the site is not big enough yet for it to be a real problem now though.


I was trilled that you posted a science topic! Thanks I find turtle evolution interesting. Although I have to admit that I was looking for something about the Earth sits on top of turtles all the way down.


Rieppel is the guy who wrote “Turtles as Hopeful Monsters,” and apart from being Mr Turtle Evolution, he has interesting views on the mechanics of macroevolution.

I think I mentioned elsewhere that he’s also a pattern cladist, so can take a discovery like this more dispassionately than some others would. The whole story of turtle evolution (like that of virtually any group one cares to look at) is about the ambiguities in the “tree of life” - hitherto (and maybe still, for all I know so far) widely different groups were posited as their ancestors, with good evidence for each.

From Mark’s summary, we have an interesting question about the proposed loss and re-evolution of beaks, and that is what it is about being turtle-like that makes that likely. They appear not to have evolved even once in most reptile groups. This seems to be an example of the falsification of Dollo’s law, a law which made good sense under even today’s evolutionary theory.


I noticed some time ago the claim that "evolution doesn’t work backwards. Lot’s of smart people assure us that it works great going forwards and I kinda get what they are saying but then we see something like this article. It is a stronger example of what we see a lot- including with what is claimed about human evolution. Different key traits show up in different families of creatures before they all show up together in the modern form. And I’m like “are you sure that’s not a sign of a Creator playing around with different features before putting them all together in one new animal? Because that looks like a Creator playing around with different features before putting them all together in a new animal.”

I don’t believe in the kind of God who needs to design test-prototypes! Nevertheless, it’s an odd thing to have features evolving, disappearing, and appearing again in a mix and match like this. It makes evolution looks like drawing existing features of a shelf as required.

It doesn’t help that in these days of neutral theory, we can’t say the features meet any particular need (though beaks and shells have stabilised out in turtles for a decidely long time now). The neutral theory doesn’t seem much better - all the genes for beaks get switched off, perhaps, but the pseudogenes miraculously hang around for millions of years until, presto changeo, they switch back on again.

It makes that old chestnut of transitional forms more fun though - “the giraffes had short necks, long legs and stripes, then long necks, short legs and stripes, then at last long necks, long legs and spots. Once you know it was all going back and forth like tennis, the transition is obvious!”

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Who said anything about “needs to”? I would have played around with it in the same situation just for fun. Wouldn’t you?

PS- I really think its more of a case of helping Creation along with obeying His commands. It is not He who needs to design test-prototypes, but the Creation which is fulfilling His commands.

“Hey guys - look at this turtadactyl - a beak, a shell AND wings!” :grinning:


I feel like I should know more about turtles. My last museum did work on them including this recent find:

But I really don’t know much about them but I could definitely talk to those who do. Including the authors of the paper of the above find. Drew Gentry was always working in the lab across from mine. Talked to him here and there.


You can never know too much about turtles! :grinning:

Having at last read the press-pieces, the real progress seems to be that it has settled the question of turtles origins in the diapsids - which occupied a good deal of Rieppel’s book.

The interesting thing is that it’s done so by opening cans of worms about mosaic evolution, and it’s still unclear how that can work. To gain a beak you lose teeth - to lose a beak you have to get the teeth back. And tout encore if you want to evolve a beak a second time. Meanwhile shells and ribs are also dancing the same polka.