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Re: Dinos' loss was not mammals' gain
Olaf R. P. Bininda-Emonds, Marcel Cardillo, Kate E. Jones, Ross D. E.
MacPhee, Robin M. D. Beck, Richard Grenyer, Samantha A. Price, Rutger A.
Vos, John L. Gittleman & Andy Purvis: The delayed rise of present-day
mammals, Nature 446, 507 -- 512 (29 March 2007)
So... they constructed a gihugrongous supertree, and fed it into a molecular
dating program after aligning 66 genes for as many species on the tree as
possible. I don't see why we shouldn't just regard the results as yet
another set of molecular divergence date estimates. 30 calibration points
were used. I'll try to get the supplementary information tomorrow to check
what they are.
The calibration points were used as minimal ages only*. Had they used
maximal ages, too, I bet the results would have been different.
* One exception: the Bathonian age of *Ambondro mahabo*, narrowed down by
fiat to 166.2 Ma, was used as the precise age of the mammalian crown-group.
Having a fixed age for the root makes molecular dating easier, but I can't
see how that justifies putting so much confidence in the Middle Jurassic
terrestrial fossil record...
There are only three outgroups in the tree: *Gallus gallus*, *Xenopus
laevis* and *Xenopus tropicalis* (...isn't that *Silurana tropicalis*?).
This increases the risk for their branch lengths having unwanted effects on
the branch lengths in the ingroup.
Just over 3 months from reception to acceptance, and just under 2 from
acceptance to publication. Fast.