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Re: Phytodinosauria status



> * << All basal dinosaurs, whether ornithischian, sauropodomorphan,
> >  or theropodan, are basally obligate bipeds; [...] >>
> >
> > I would disagree with this statement. The basalmost dinosaur could well
> have
> > been an obligate semisprawling quadruped (and arboreal into the
bargain).
> If,
> > as I think, the forelimb evolved gradually into a functioning wing
> > (progressively losing its outermost digits in the process) in a lineage
of
> > arboreal dinosaurs,
>
> Here you IMHO run into the same problems as Feduccia -- why should the
> forelimbs (and only they) evolve into wings in a quadruped, and why should
> they lose digits in an arboreal animal???<<
> *
> * The fingers get in the way of feathers?

Mmm... did I say that? ~:-| I didn't mean to, anyway. I wanted to say that,
as others have mentioned, a four-legged climber that begins to jump and
glide should end up with either no extremities (*Draco volans*,
Weigeltisauridae, Kuehneosauridae) or all (all gliding mammals; bats)
involved in the wings.

> I was talking to Phil Currie
> recently and we were talking about the third digit in early birds and how
he
> thought that they would have been enclosed in skin. I told him that I've
> seen two Confusisornis specimens that have the third digit perpendicular
to
> the other two fingers, in both wings. So, the feathers were over/on top of
> the digits.

Definitely. Apparently *Confuciusornis* was able to grasp between digits I
and III (while II, with its reduced claw, supported the primary feathers).

> > then the much larger ground-dwelling offshoots of this
> > lineage should display a trend away from quadrupedality toward
> bipedality:<<
>
> Apparently prosauropods and ornithischians display the opposite trend.<<
> *
> * Ah yes, Dryosaurs, hypsilophonds were quadrapedal.
> *

?
Is this ironic? I don't understand...

> > So: most primitive are the sauropods (still have the fifth toe), [...]
> > Next, prosauropods and ornithischians (fifth toe reduced or
> > absent, with mt V just a splint), then herrerasaurians, then other
> theropods,
> > etc.
>
> Losing the fifth toe is very easy, it seems. Considering how many times
> mammals have done it... and that *Psittacosaurus* has very reduced fourth
> and fifth fingers, unlike neoceratopsians...<<
>
> So, what mammals regrew them? None, that I know of. Of course I don't
really
> know mammals that much, but I disagree with 're-evolution' of a complete
and
> functional digit.

So do I. I should have elaborated more that I wanted to say that
*Psittacosaurus* must have reduced its IVth and Vth fingers independently of
everyone else, because neoceratopsians retained a more plesiomorphic
condition. In short, digit loss occurs all the time, and digit re-evolution
never.

> > A lot of this evolution happened in the Middle Triassic or even earlier,
> > among small forms (e.g., lagosuchians, which by their feet
>
> and, AFAIK, only by their feet
>
> > fit best between
> > herrerasaurians and later theropods);<<

> Ah, sarcasm.

No, why? I'd have added a smiley, such as B-) or :-> , if I had intended to
be sarcastic --


AFAIK, several plesiomorphies put them outside Dinosauria.

> This requires the existence of lots of undiscovered basal dinosaurs and
more
> basal dinosauromorphs with closed acetabula. AFAIK all basal
dinosauromorphs
> have partly open acetabula, haven't they?<<
>
> Then all the dinosauromorphs have been found and we know them all, right?

My error: "AFAIK all KNOWN basal dinosauromorphs"... and of those the ones
for which acetabula are known.

> Wait till you see what's coming from Europe!!!

Looking forward! :-9