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Re: turning turtles

--Original Message-- From: Bill Adlam <sagitta_elegans@yahoo.com>To:  list :
Wednesday, February 24, 1999 04:28 PM

>I've now got my hands on the Hedges & Poling turtle  paper in Science.
>It's entitled 'A molecular Phylogeny Of Reptiles' (by reptiles they
>seem to mean all non-mammalian amniotes).
>To summarise, the maximum likelihood phylogeny, based on 11 nuclear
>proteins (1943 amino acids) was:
>(Rodents + Primates) + (Squamates + (Birds + (Crocs + Turtles))).
>Tuataras weren't included due to lack of data.
>A consensus phylogeny based on 4 genes (785 amino acids)
>(Rodents + Primates) + (Squamates + (Turtles + Crocs + Birds +
>To me the big surprise is not so much that turtles are grouped with
>archosaurs as that they come within archosaurs, closer to crocs than
>to birds.  This node is very strongly supported, with various
>techniques giving confidence measures of 97 to 100%.  The
>turtle-croc-bird node is supported 66 to 90%.

Proteins behave differently at different temperatures.  Warm-bloods might be
expected to have protein strucutres that worked well over a limited range,
but "cold"-bloods probably have pressures converging their proteins to
optimum behaviour over a wider range of temperatures.  I would expect a
clustering effect inside groups with similar thermal modes.