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ARCHOSAURIAN TURTLES?




<<The theory of relativity does predict events not available for study,
but so does cladistics. You said yourself we don't have all the
fossils, and one doesn't always get an "answer" they were looking for.
Take Olivier Rieppel at the Field Museum whose recent cladistical
analysis suggests turtles may be archosaurs! Since the common
"accepted" hypothesis was that turtles represented anapsids, the most ancient and "primitive" reptiles, Rieppel should have gotten what everyone else did if there was no real predictive power or everything was assumptions in cladistic methodology. Instead, many researchers have good reason to go back and look at turtles more seriously. Are they archosaurs? That's the risky prediction, without lots of fossils pointing the way.>>


Sorry in advance for the small font that hotmail sends out on every email. It truly isn't my fault.

Rieppel didn't suggest that turtles were archosaurs, that was Hedges and Poling (1999). Rieppel found out in his 1993 analysis trying to determine sauropterygian ("euryapsid" in the paper) relations, that turtles fall basal to diapsids (above captorhinids) as a whole with the particular data set he was using. Most prominently with Michael DeBraga (1997), Rieppel found that turtles are probably lepidosauromorphs, based on several features but most prominently the advanced mesotarsal ankle joint (note that Hedges and Poling have turtles as closer to crocodilians than birds, but it is the bird group that has the AM ankle). Rieppel (1999) summarized his findings quite eloquently in his commentary on Hedges and Poling's molecular analysis. Also of interest is that he cites a paper in prep with Riesz that shows (as his many earlier analyses did) that sauropterygians are probably the closest relatives to turtles. Rieppel (1998) shows Testudines as a sister-group to thallatosaurians+sauropterygians (another new arrangement).

I take this over Lee's turtle origins stuff.

Matt Troutman
m_troutman@hotmail.com


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