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Re: Protungulatum index; pterosaur finger. + Hennig comb



----- Original Message -----
From: "John Bois" <jbois@umd5.umd.edu>
Sent: Thursday, July 11, 2002 10:43 PM

> > Actually... I thought we were talking of how the very last pterosaurs,
all
> > of which were, as far as known to date, gigantic azhdarchids, died
out. --
> > Few really small adult pterosaurs are known. Adult *Rhamphorhynchus* and
> > *Pterodactylus* reached over 2 m wingspan.
>
> No, I think we are talking about the long decline including the
> denumen--why did small pterosaurs disappear?  It's a worthy question.  If
> specific birds did it, then these same birds may well have had an effect
> on other bird competitors.

I see. But still, really small adult pterosaurs aren't known, which may or
may not tell something, and if specific birds did it, why should these same
birds have done in Enantiornithes plus the giant pterosaurs _50 million
years later_?

> > > [...] feathers confer greater manueverability to creatures of equal
size
> > > [...]
> >
> > [...] cambered wings of bats give them the great
> > maneuverability [...]
>
> Right.  But pterosaurs had fewer adjustable wing surfaces, right--one
> finger, primarily

Well... 3 on the whole: a propatagium between elbow, shoulder and wrist
(pteroid bone), a brachiopatagium between 4th fingertip, trunk and at least
in some the knees, and a cruropatagium between the legs of at least some
(such as *Sordes* and *Jeholopterus*). But anyway, no pterosaur with a
typical bat lifestyle is known so far.

> (unless all the fossils morphed since Romer was writing
> back in the Jurassic).

Mmm... many of them actually did. There have been more extreme effects than
rising dinosaur tails. :-)

> > > - just as bats are banished (largely) from the day niche by birds, the
> > even less effective pterosaur fliers would be prey to Cretaceous
> > >equivalents (if any existed!)--predation is the key, here
> >
> > Just as passerines keep albatrosses from flying during the day --
oops...
>
> How does this relate?

Different ecological niches. It doesn't look like pterosaurs and birds
competed, unlike insectivorous bats and insectivorous birds that would
compete if they weren't segregated by time.

> > > -baby pterosaurs must be nurtured for longer than baby birds because
they
> > > are heavier and develop less thrust than baby pterosaurs (going out on
a
> > > speculative limb here).
> >
> > So speculative that I needn't even answer IMHO. Why "less thrust"?
> > Azhdarchids had powerful flapping abilities.
>
> There must be some science on this: how big must a juvenile feathered
> creatured be relative to a non-feathered juvenile?

What effect should age have here?

> I don't see why this should be speculative.

Firstly, you called it so. :-) Secondly, _nothing_ is known about baby
azhdarchids AFAIK.

> It's as if there is no value at all to
> feathers--which is why I asked the question in the first place.

Well... maybe... maybe there is no value at all to feathers, compared to a
patagium*. :-)

* Is there a more English expression? There's a more German one. My
dictionary isn't scientific enough to know either.

> > > This additional PI costs
>
> [...] Parental Investment.

OIC.

> > You're forgetting that
> > 1. rheas still aren't extinct. Even though for most of the Cenozoic
there
> > were predators that were able to run after them -- phorusracoids.
>
> [...]

I mean, even when rheas were in danger throughout their lives, not just as
eggs and young, they didn't die out. Now the adults are pretty safe, aren't
they, so their situation has already been worse?

> Pterosaurs are elegant and speedy walkers compared to what?

Penguins. Albatrosses. Maybe even ducks. I'll have to dig up the paper... I
remember a calculated speed of 1 m/s, even though the pterosaur was
relatively small.

> > > --must watch their babies more carefully.
> >
> > Maybe they did :-)
>
> All egg layers must.

Many don't. Turtles for instance.

> > One more question: Why didn't *Boluochia*, a real fossil
falconiform-mimic
> > bird, take over the world in the mid-EK?
>
> No idea.  And I'm not arguing that one bird--the falconiform if it
> existed--took over the world.  I'm only using it as an example.

So do you consider this specific example falsified?

------------------------
Now that I got used to counting spaces to make cladograms line up in
monospace fonts while Outlook Express displays plain text as Times New
Roman, I'm learning that there are people outside Europe who write
plain-text mails in such a program! :-) Here are both presentations of the
cladogram, lining up in Times New Roman:

--+--+------------A
    |    `--+--+------B
    |         |     `--+--C
    |         |          `--D
    |         `---------E
    `----------------F

--+--F
    `--+--A
         `--+--E
              `--+--B
                   `--+--D
                        `--C

Hope this helps. :-]