New stem-turtle Pappochelys rosinae

[stemturtle]

A new stem-turtle, Pappochelys rosinae, was discovered in Germany. Pappochelys has a diapsid skull, and at 240 MY is midway between Eunotosaurus and Odontochelys. Turtles are sister group to Sauropterygia. Thanks to amargasaurus cazaui for alerting me to this news. https://app.box.com/s/vm4mfkfk8z6cpoja9firy117ahb65iuu

[amargasaurus cazaui]

A new stem-turtle, Pappochelys rosinae, was discovered in Germany. Pappochelys has a diapsid skull, and at 240 MY is midway between Eunotosaurus and Odontochelys. Turtles are sister group to Sauropterygia. Thanks to amargasaurus cazaui for alerting me to this news. https://app.box.com/s/vm4mfkfk8z6cpoja9firy117ahb65iuu

A stem turtle here...a stem turtle there...everyone should have a  stem turtle !!!!

[CityRaptor]

Papo should make one.  Papo Pappochelys 

Guess we also finally know where turtles belong.

[amargasaurus cazaui]

Stemturtle is easy to shop for...I go through the Paleowiki listings once a day to see what books, articles of papers can be gleaned. I grab anything dinosaur related and if anything says turtle in the title I post it to Mr. Stemturtle...if anyone else has a single word topic for me to watch for........

[Balaur]

So, sister group to Sauropterygia... That's interesting and cool!

[Balaur]

Actually, now that I think about it, I'm not sure if we can say that the phylogenetic placement of turtles is closed and solved. Listening back to a few episodes of the Tetrapod Zoology Podcats, Darren Naish seems to think that we've been duped by morphology. He mentions that most genetic studies seem to place turtles within archosaurs. I think it's a matter of what do we believe in more. Morphology can get us an idea of what are the defining features of an animal, but we also have to consider the possibility that they might have convergantly evolved. I'm more inclined to go with genetics right now... Oops, I should've read the paper before posting all of this. Also, does anybody know where in Diapsid's Eunotosaurus belongs too?

[SBell]

Actually, now that I think about it, I'm not sure if we can say that the phylogenetic placement of turtles is closed and solved. Listening back to a few episodes of the Tetrapod Zoology Podcats, Darren Naish seems to think that we've been duped by morphology. He mentions that most genetic studies seem to place turtles within archosaurs. I think it's a matter of what do we believe in more. Morphology can get us an idea of what are the defining features of an animal, but we also have to consider the possibility that they might have convergantly evolved. I'm more inclined to go with genetics right now... Oops, I should've read the paper before posting all of this. Also, does anybody know where in Diapsid's Eunotosaurus belongs too?

You could have just modified your post! 

I was listening to Hans Dieter-Sues talk about the find on the radio today, and he explained it pretty nicely; basically, turtles's skulls 'lost' the characteristic two holes of the diapsids. So they are nested in there pretty convincingly. Or as he said it, turtles are directly related to the reptiles; not part of the early stem tetrapods. He actually referred to their group as 'reptiles' because that man has been doing this a long time--and knows how to make sure an audience can understand what he's talking about.

[Balaur]

Actually, now that I think about it, I'm not sure if we can say that the phylogenetic placement of turtles is closed and solved. Listening back to a few episodes of the Tetrapod Zoology Podcats, Darren Naish seems to think that we've been duped by morphology. He mentions that most genetic studies seem to place turtles within archosaurs. I think it's a matter of what do we believe in more. Morphology can get us an idea of what are the defining features of an animal, but we also have to consider the possibility that they might have convergantly evolved. I'm more inclined to go with genetics right now... Oops, I should've read the paper before posting all of this. Also, does anybody know where in Diapsid's Eunotosaurus belongs too?

You could have just modified your post! 

I was listening to Hans Dieter-Sues talk about the find on the radio today, and he explained it pretty nicely; basically, turtles's skulls 'lost' the characteristic two holes of the diapsids. So they are nested in there pretty convincingly. Or as he said it, turtles are directly related to the reptiles; not part of the early stem tetrapods. He actually referred to their group as 'reptiles' because that man has been doing this a long time--and knows how to make sure an audience can understand what he's talking about.

Oh, I believe that turtles are diapsids, (I never believed that they were Anapsids or Parareptiles) but I'm just skeptical that they are a sister taxon to Sauropterygian's.

[Halichoeres]

The most common molecular result I've seen lately (last 6 or 7 years) is that turtles are sister to the crown Archosauria, but they could simultaneously be the sister to the crown Archosauria AND sister to the Sauropterygii, theoretically, if it turns out that sauropterygians are archosauromorphs. That is, they're not mutually exclusive propositions. That would make sauropterygians stem turtles, which should make stem-turtle very happy. 

[Dinoguy2]

The most common molecular result I've seen lately (last 6 or 7 years) is that turtles are sister to the crown Archosauria, but they could simultaneously be the sister to the crown Archosauria AND sister to the Sauropterygii, theoretically, if it turns out that sauropterygians are archosauromorphs. That is, they're not mutually exclusive propositions. That would make sauropterygians stem turtles, which should make stem-turtle very happy. 

This is exactly what a 2013 study found that combined molecular and morphological data. When they ran a morphological analysis constrained by the molecular data, turtles were archosauromorphs and so were sauropterygians. Some recent studies have even pulled ichthyosaurs into this group!

[stemturtle]

Grandfather turtle is important as a transitional fossil, so I am pleased to see responses from our members: amargasaurus cazaui, CityRaptor, Balaur, SBell, Halichoeres, and Dinoguy2. Thanks for your comments.

The cladogram in the paper that places turtles as sister group to sauropterygians is an hypothesis. We can expect to see it challenged. I like the idea of classifying sauropterygians as archosauromorphs. Stay tuned for future developments.

[Plasticbeast95]

If turtles are placed in the archosauromorpha, does that mean they have a secondarily anapsid condition? Perhaps caused by the same pressures that resulted in the evolution of a shell?

[Halichoeres]

If turtles are placed in the archosauromorpha, does that mean they have a secondarily anapsid condition? Perhaps caused by the same pressures that resulted in the evolution of a shell?

The anapsid condition is almost certainly secondarily derived, as both morphological analyses of fossil taxa and molecular analyses of extant taxa routinely find turtles nested within the Diapsida at the very least. They have strange masseter attachments as a corollary, and the evolution of that condition probably did go concurrently with shell evolution.

[Plasticbeast95]

If turtles are placed in the archosauromorpha, does that mean they have a secondarily anapsid condition? Perhaps caused by the same pressures that resulted in the evolution of a shell?

The anapsid condition is almost certainly secondarily derived, as both morphological analyses of fossil taxa and molecular analyses of extant taxa routinely find turtles nested within the Diapsida at the very least. They have strange masseter attachments as a corollary, and the evolution of that condition probably did go concurrently with shell evolution.

I see, interesting...

[stemturtle]

I came across a blog in Scientific Ramblings that concludes with comments on the possible ancestry of the early stem-turtles: "Eunotosaurus, Pappochelys and the crisis in reptilian phylogeny". The blogger, manasataramgini, calls the gap between the first diapsids and the split into archosauromorphs and lepidosauromorphs a period of "great obscurity." While we wait for greater resolution, I am content with the hypothesis of descent from Eunotosaurus to Pappochelys to Odontochelys.