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Re: Large last gasp of pterosaurs




On Wed, 21 Jan 2004, James R. Cunningham wrote:

> Essentially, I do think the impact triggered a period of weather
> unsuitable for soaring flight.  Pterosaurs in general were unable to fly
> continuously by other means. If they can only 'crow hop', they don't
> feed.  If they don't feed, they don't survive.  That's not circular.

OK.  This is  a reasonable hypothesis.  And this is a casual dialogue.
But unfortunately many consider this a closed case.  There is no direct
evidence of bad flying weather.  Without that all you have is the timing.
And, as I have argued, you can't use one phenomenon (disappearance of Q)
to support the effects of another phenomenon (K/T weather).  Nor can you
use an unkown phenomenon (K/T weather) to support a causative hypothesis
of Q extinction--but I'm getting quite dizzy thinking about it.

A big yes on your discussion of energetics.  Thank you.

> > I understand
> > about vultures being able to stay aloft, and eagles diving on prey--but
> > how do you see this in relation to Q. and would-be bird
> > competitors/predators?
>
> See above.  Also think about the competition between vultures and
> hyenas.

Different, I think: aerial vs. terrestrial scavangers.

> You're making the implicit assumption that pterosaurs are more subject
> to predation by birds than birds were subject to predation by birds.
> Why is that?

Birds were more likely to be on even footing with other birds because of
morphological similarity.  Ptrerosaurs were different.  I'm hypothesizing
this difference led to a deficit on land, that they lacked terrestrial
agility relative to birds.

> What makes you think that pterosaurs were particularly limited in their
> terrestrial agility?  I've not seen any evidence of that in either their
> skeletons or their trackways.

I'm a victim of pop science portrayal of guy on crutches hypothesizing Q
terrestrial movt on Making of WWD--was this way off?  Sorry.

> > you would want to distance
> > yourself from predators--this is especially true if you are migratory and
> > have the choice of remote/low predator density locations, e.g., geese,
> > albatrosses, penguins.
>
> Should I take this as an expression that access to remote locations
> provide equal advantages to both pterosaurs and birds capable of making
> the flight?  I have no problem with that.

Yes.  But if birds became able to reach previously inaccessible
places...then the competition/predation could begin for remote laying Q.
just as it had for more local pterosaurs.

> > But the guess is informed by the problems
> > and amazing solutions supplied by extant birds.  I do feel that in an
> > Olympic games of nesting, birds would win.
>
> This is a leap of faith that I can't follow.  Show me solid proof and
> I'll let you lead me by the hand.  This appears to me to be the essence
> of your argument. Is it?

Yes. And I would be very interested to hear your opinion of ptrerosaur
nesting habits.  I suppose the best extant models would be island
battles--bird on bird at nesting sites.  It's quite ferocious.  Birds seem
able to hover and snatch (how about small pterosaurs?)  And then my
impression is that birds are able to compact themselves more than
pterosaurs--i.e., access more hidden nest sites.

>   This is not to say
>   that birds did not also have amazing abilities--just that pterosaurs
> may
>   have had the edge here.

Hey, you know what--I'm guilty of the same circularity as the bolide
arguments for Q. extinction: birds must have had the edge because
pterosaurs are extinct.