Re: synapomorphies not created equal

["David Marjanovic" <david.marjanovic@gmx.at>]

>       In my opinion, the one synapomorphy of Mammalia, the movement of the
> three ossicles from the mandible into the ear of the first mammals, was
> strongly selected for and occurred relatively rapidly.  It is thus a very
> strong synapomorphy.

Not much has migrated here*, the real feature here is the new jaw joint
between the squamosal and the dentary. The whole rear half of the lower jaw
was involved in the ear in early therapsids (the logical place for animals
stemming from rather deaf lizardlike ancestors that spent most of their time
with their lower jaws lying on the ground). Regarding the fact that
*Probainognathus* had _another_ new jaw joint -- between the _surangular_
and the squamosal --, I'm not sure that the dentary-squamosal joint was so
terribly unlikely to evolve twice (though I won't doubt that it didn't,
given our present knowledge of the fossil record).

*Though the bones do migrate in the ontogenies of living mammals.

>      In fact, that one mammalian synapomorphy may be stronger than all the
> dinosaur synapomorphies (proposed by Sereno and /or Gauthier) put
together.

>       I've been thinking very hard about this, and I am still not
convinced
> that all synapomorphies are created equal.  Some are "stronger" than
others
> no matter how long or big the evolutionary gap happens to be in which it
> falls.

This is simply not the issue. The issue is parsimony, which only involves
large _numbers_ of synapomorphies.

>   One mammalian synapomorphy has stood the test of time, for a very long
> period of time.

IMHO it's just coincidence that people got it right from the beginning :-)

> The fact that Gauthier and Sereno felt compelled to compile
> a long list of dinosaur synapomorphies indicates to me that they have no
> strong confidence in any of them.

To the contrary. The longer the list, the more stable the node. Confidence
isn't parsimonious.

>      This almost cries out for the need for these purported synapomorphies
> to be evaluated, and that the strongest be identified and carefully
> scrutinized.

Of course -- it's science after all! :-)

> The therapsid-to-mammal transition is just as well documented
> (if not more so) as that of the transition to "non-dinosaurs" to
dinosaurs.

A lot more so, rather like the beginnings of birds.

> Therefore the lack of a strong synapomorphy in the latter should be taken
as
> a strong signal that a comprehensive reevaluation is required.

Not in the least. Nothing against a comprehensive reevaluation, aka
scientific testing, but nothing is crying for that at the moment.

> I believe than Crurotarsi will probably not
> survive, and it is still a toss-up whether Dinosauria will survive as a
> clade.

Why? Please tell us why... :-)

> Therefore those who have challenged me to come up with an
> alternative set of synapomorphies

along with an alternative phylogeny -- few people will believe you if you
just say "however it was, it was not _that_ way"...