[Taxacom] More evidence turtles are diapsids

[John Grehan]

In this case the morphology may corroborate the molecular prediction,
but what would have happened if it did not? Would the morphological
evidence have just been dismissed as it is in the hominid field?

I read the arguments over testing and deduction, which seem to have been
around for as long as I can remember. Whether or not it is a 'test' or
not, morphology represents a source of evidence that may or may not
corroborate linear molecular similarity. If the results of each are
incongruent the decision to accept the molecular result renders the
fossil record for that group uninformative. This is what has happened
with Ardipithecus where the fossil is said to belong to a group that
cannot be substantiated by any direct evidence and yet this is able to
be said without anyone batting an eyelid.

John Grehan



> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> bounces at mailman.nhm.ku.edu] On Behalf Of mivie at montana.edu
> Sent: Friday, October 16, 2009 12:20 PM
> To: Kenneth Kinman
> Cc: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] More evidence turtles are diapsids
> 
> This turtle study is an excellent example of how the
> molecular-morphological issue SHOULD work.  There is an established
> morphology-based system, challenged by new data from molecules,
setting up
> a test of competing hypotheses.  The test then causes new character
> systems to be found and evaluated, leading to progress in the
> whole-evidence understanding of the group.
> 
> Why this is so seldom done in the great apes is a mystery.  The recent
> Discovery special on Ardi was a perfect example of nonsense
pseudoscience
> being presented to the  public about great ape origins.  In the
program,
> they kept saying they expected a human ancestor that was chimp-like,
> showing a phylogram with chimps and humans having a most recent common
> ancestor. Then, when they found something non-chimp like, they just
drew
> the same phylogram LONGER!  They never dealt with the idea of
refutable
> hypotheses, nor that fact that the common ancestor of humans and
chimps
> (at whatever level it existed) would not be expected to look like
either.
> No wonder so much of the public has a misunderstanding of evolution if
we
> teach them about it with such sensational and misleading stuff!
> 
> Makes me understand more why this drivel drives John G over the edge.
> 
> Mike Ivie
> 
> 
> 
> > Dear All,
> >       A recent paper provides more evidence that turtles are well
within
> > the diapsid clade of reptiles (and therefore not true anapsids).
The
> > citation and abstract are given below.
> >      Note that they use the clade name "Pantestudines" in the title,
> > which I believe should actually be spelled "Pan-Testudines".  If we
are
> > going to have to put up with all these new PhyloCode clade names,
the
> > "Pan-" names should be hyphenated to clearly distinguish them as
such
> > (and I believe that PhyloCode is going to mandate this).
> >       --------Ken Kinman
> > ------------------------------------------------------------
> > An Archosaur-Like Laterosphenoid in Early Turtles (Reptilia:
> > Pantestudines); by Bhullar and Bever, 2009.   Breviora, 518:1-11.
> >
> > Abstract
> > Turtles are placed with increasing consistency by molecular
phylogenetic
> > studies within Diapsida as sister to Archosauria, but published
gross
> > morphology-based phylogenetic analyses do not recover this position.
> > Here, we present a previously unrecognized unique morphological
> > character offering support for this hypothesis: the presence in stem
> > turtles of a laterosphenoid ossification identical to that in
> > Archosauriformes. The laterosphenoid is a tripartite chondrocranial
> > ossification, consisting of an ossified pila antotica, pila
metoptica,
> > and taenia medialis + planum supraseptale. It forms the anterior
border
> > of the exit for the trigeminal nerve (V) and partially encloses the
> > exits for cranial nerves III, IV, and II. This ossification is
unique to
> > turtles and Archosauriformes within Vertebrata. It has been
mistakenly
> > dismissed as anatomically dissimilar in these two groups in the
past, so
> > we provide a complete description and detailed analysis of
> > correspondence between turtles and Archosauriformes in each of its
> > embryologically distinct components. A preliminary phylogenetic
analysis
> > suggests other potential synapomorphies of turtles and archosaurs,
> > including a row or rows of mid-dorsal dermal ossifications.
> >
> >
> >
> >
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