Origin of turtle shell

[stemturtle]

A paper in Current Biology, Evolutionary Origin of the Turtle Shell, re-examines Eunotosaurus as a stem-turtle.  Candidacy of this Permian parareptile will face challenges from the archosaur camp of turtle ancestry as that molecular evidence continues to build.

[stemturtle]

Chuckwalla, Sauromalus alter (Skillcraft)

Here is the best approximation of a Eunotosaurus model that I could find.  It is the chuckwalla from the Skillcraft Reptile and Amphibian kit.  Length is about 6 inches (15 cm.). Juveniles can have a color pattern similar to the popular restoration of Eunotosaurus.  The chuckwalla would make a more convincing representation if it had swallowed a tennis ball.   

EDIT: The correct spelling for Skillcraft is Skilcraft.  My bad.

[tyrantqueen]

Nice model, I have the Skillcraft chuck too. Did you paint it yourself?

[stemturtle]

Nice model, I have the Skillcraft chuck too. Did you paint it yourself?

Thanks, Tyrantqueen.  Yes, I painted it to illustrate this topic.  Over 40 years ago, I saw several chuckwallas in the desert while taking a field class at the UC Riverside.  I prefer the drab, adult coloration.  I did not link to your walk-around of the chuckwalla in the Animal Toy Forum because the image would not load.  Let's hope it starts working again.

[Balaur]

That's actually a really cool news item. I thought that Euntosaurus wasn't a turtle ancestor. It does look like a turtle. That's really cool. I am very intrested in how evolution creates such awesome creatures, and right now I'm very intrested in pterosaur evolution, and I think that turtle evolution is very cool.

Turtles all the way down. 

[stemturtle]

That's actually a really cool news item. I thought that Euntosaurus wasn't a turtle ancestor. It does look like a turtle. That's really cool. I am very intrested in how evolution creates such awesome creatures, and right now I'm very intrested in pterosaur evolution, and I think that turtle evolution is very cool.

Turtles all the way down. 

Here is a link to an article by Michael Lee responding to the hypothesis that Eunotosaurus is a stem turtle, "Turtles in Transition."

If the genomic evidence is true that turtles and archosaurs are sister groups, then:
analysis is required to reclassify Eunotosaurus as an archosaur rather than a parareptile, or
if Eunotosaurus is a parareptile then it shows convergent evolution with turtles in the development of the shell.
Lee would like to see further studies, especially about shared characteristics of the skull of Eunotosaurus and the skull of turtles.

It will be fascinating to follow future developments.