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RE: Morpho v molecular (was Re: Tinamous: living dinosaurs)



Tim Williams wrote-

> Yes, but as you say, this study relies upon total evidence (morphology
> + molecules). As Spaulding &c themselves put it: "Trees based only on
> data that fossilize continue to show the classic arrangement of
> relationships within Artiodactyla with Cetacea grouping outside the
> clade, a signal incongruent with the molecular data that dominate the
> total evidence result." And among the other morphology-based studies
> mentioned by you are phylogenies that are at odds with both the
> "classical" topology (Artiodactyla and Cetacea as sister taxa) and the
> topology given by molecular-based phylogenies (Whippomorpha as the
> sister taxon to ruminants).
>
> So the Whippomorpha issue is 'messy' to say the least. The topology
> of Cetartiodactyla as given by molecular-based methods has varying
> support from fossil/morphological studies. Paleontologists who find
> support for some kind of hippo-whale clade (Cetancodonta/Whippomorpha)
> do not necessarily agree on the content and relative position of this
> clade.

Yet as I said, even using morphology-only, Spaulding et al. only barely 
supports cetaceans being outside of Artiodactyla.  Not enough to say morphology 
rejects Whippomorpha in my opinion.

And to answer David's question about the cetartiodactyl analyses, no the 
characters were not ordered. :|

As for the content and position of Whippomorpha within Artiodactyla, well 
that's a different matter.  A whippomorph-ruminant clade is pretty 
unparsimonious in Spaulding et al.'s data- it takes 31 more steps.  But there 
are lots of ways molecules conflict with morphology in current analyses.  In 
Squamata, molecular phylogenies don't have Scleroglossa.  In Mammalia, they 
don't have Ungulata.  Similarly, there are many molecular relationships that 
aren't backed up by morphological evidence (like you say for archosauromorph 
turtles), especially since many groups have historically been seen as bushes 
whose interrattionships are generally unknown (Percomorpha, Neoaves, 
Placentalia).  But remember my original statement was "I don't know of any 
molecular-based relationship which is consistantly found and which workers 
believe is wrong."  In none of these cases do most people think the DNA is 
wrong.  They generally recognize the morphological analyses suck, and the 
molecular analyses suck less, so they go with the latter.  When the two methods 
consistantly give different topologies, it's always the addition of new taxa 
and characters to morph analyses that move things closer to molecular results 
(e.g. the recently discovered amphibeanean fossil with lacertid charaxcters, 
which molecules predicted).  You never see more genes and sequenced taxa 
leading to molecular results that resemble the traditional morphological 
results after all.  The changes always seem to go one way.

Mickey Mortimer