Re: dinosaur synapomorphies?

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

>       Sereno himself points out that some of these synapomorphies are not
> present in Sauropods or other groups of dinosaurs.

A few reversals...

> And many of these
> synapomorphies involved the pelvis and hind legs, and being interconnected
> changes in the evolution of an "abductor-based balancing system", they
could
> have happened more than once (just like the development of the perforate
> acetabulum).

These are much easier to compare with outgroups -- *Lagerpeton* is AFAIK
still known only from its hindlimbs.
Isn't the _semi_perforate acetabulum still a valid character?

> In my opinion, skull character 1 is very weak.

IMHO it's very strong -- AFAIK everyone else except mammals and their close
relatives has postfrontals.

> I'm just
> looking for a few "strong" synapomorphies that I can really believe in,
but
> am not having much luck so far.  If there are a couple of strong ones,
then
> weaker ones can be used to support a case for holophyly for dinosauria.

Parsimony is not enough for you? :-)

And... where else should the dinosaurian groups have come from? I don't know
any better ideas than dinosaurian holophyly. (Old ideas that e. g. sauropods
descended from rauisuchians are IMHO totally refuted because people nowadays
know much better what a rauisuchian is than in the 60s.)

My comments to those characters I can comment:

> >>1. Postfrontal absent

or fused to postorbital very early in ontogeny; strong

> >>2. Frontal participates in supratemporal fossa

Does *Shuvosaurus* have it? Associated with jaw muscles, unrelated to
locomotion except maybe via metabolism; strong

> >>5. Posttemporal opening reduced to small foramen

Sounds very strong, but I don't know what the posttemporal opening is! :-]

> >>6. Dorsosacral (3 sacrals)

Wrong, see recent work by Galton.

> >>7. Ossified sternal plates present

I've seen that as a synapomorphy of _Diapsida_.

> >>9. Manual digit IV narrower than digits II and III without terminal
ungual

We need hands from other dinosauromorphs; anyway this is a very strong
character, showing the unique genetic decoupling of fore- and hindlimbs.
*Cosesaurus*, which superficially looks a lot like a lagosuchian, has much
more normal hands with a very long finger IV that AFAIK retains 5 phalanges
including a claw, and V is very short but still has a claw (unfortunately
www.pterosaurs.net is still not accessible). No dinosaur has more than 3
phalanges in finger IV.

> >>13. Cnemial crest present
> >>14. Astragalar ascending process present

Adaptations to erect-limbed cursoriality.

> >>18. Metatarsal IV shaft sigmoid in anterior view
> >>
> >>[...] Sereno codes [...] Sauropoda lacking [...] 18

Graviportal adaptation.