Monday, December 01, 2008

Special Shout-Out to Nick Gardner

I have to thank Nick Gardner, who as you may remember, hates theropods. He (and Will Baird, actually) has been hounding me about my mispeakings regarding Odontochelys and turtle origins. I have never understood the morphological basis for a diapsid origin for turtles, and grew up with the dogma that Testudines are the only living group of anapsids whose closest (extinct) relatives were the pareiasaurs like Scutosaurus.

Well, Nick pointed me in the direction of an important paper by Reippel & Reisz which gives said morphological basis. I would be remiss were I not to pass this information along:

Rieppel & Reisz (1999). The origin and early evolution of turtles. Annu. Rev. Ecol. Syst. 30: 1-22.

And I found an alternate, albeit much older opinion by William Gregory comparing turtles to pareiasaurs and placodonts. Although probably outdated, this paper contains absolutely wonderful illustrations. You don't see this anymore.

Gregory, W. K. (1930). Pareiasaurs versus placodonts as near ancestors of turtles. Bull. Am. Mus. Nat. Hist. 86: 275-326.

I will have more to say on this topic after fully digesting both papers. Thank again, Nick!

1 comment:

Will Baird said...


Geneticists are not that whacked out. Their work is another tool and we need to look at what they have and calibrate it based on the fossil record: there may be instances where the genetic clock they are working with has sped up and slowed down.

Two thoughts: first that the anapsids might be a early divergence from the diapsids. It's always possible that the Permian anapsids are completely unrelated to chelonia too.

OTOH, I have to wonder, based on these new fossils, if turtles are really monophyletic. It looks like there are two different, very different, lineages here with the osteoderms and without.

Then again, I could be completely wrong. It's happened before! Really!