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Re: turtles, mammals and rattlesnakes...
>> According to the NH article, turtles evolved during the Permian period
>> from a group of animals known as pareiasaurs. What I'm wondering is
>> a) how secure is the conclusion that turtles arose via that lineage,
>> and b) given that we accept it, how much help does that give us in
>> determining where the turtle/snake/mammal splits occurred?
>This probably refers to the work by Michael Lee, who has described several
>shared derived characteristics linking turtles to pareiasaurs. I believe it
>has been published in Science. I have seen him present this work, and
>discussed it with him, and it seems very convincing. As pareiasaurs were
>previously thought to be a sister group to Chelonia, I don't see how this
>adds to the mammal/reptile relationship debate..
At present, I believe that there are two main camps concerning turtle
origins. Both agree that turtles are within a group (Parareptilia) which
contains several extinct forms. Lee favors a relationship with
Pareiasauria. Reisz and others think that pareiasaurs are the sister group
to the Chelonia-Procolophonida clade (procolophonids are small forms which
looked like fat spiky lizards). Personally, I'm a little far removed from
this debate. Either idea seems reasonable to me.
Thomas R. HOLTZ
Vertebrate Paleontologist, Dept. of Geology