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Re: Copeing with mammals
> > It argues _for_ some kind of deficit relative to other clades.
> How? How does it?
Please. _If_ it was long and slow, there are only two possible
hypotheses. A gradual global replacement by better competitors,
or an incredible run of bad luck. To argue the latter you have to say
that if a pterosaur died out there was always a neornithine competitor
waiting in the wings (as it were),
Well. -- It doesn't have to be "always", a majority will suffice; and
"waiting in the wings" is probably a stronger expression than necessary,
it's enough if birds were for some reason able to evolve into empty niches
faster than pterosaurs in (again) a majority of cases.
And this boils down to the same thing.
Not in the least. In the first scenario, birds can actively push pterosaurs
out of ecological niches; in the second, they can only evolve into empty
So, I'm afraid you'll have to make your bed in a massive terminal
With that kind of fossil record next to nothing can be said about this.
> > I have proposed a reasonable problem--that juveniles (or adults, for
> > that
> > matter) were not as agile in the air as neornithines, and were
> > therefore
> > more susceptible to predation/general harrassment.
> But you haven't provided any shred of evidence for this speculation.
Most agree that the two clades had significantly different flight
Then why don't you take a look at precisely what those differences are, and
use that knowledge to _base_ a hypothesis of competition upon it?
> The keyword is "if". Not to mention the problems associated
> with evolving into an occupied niche.
But that is exactly what better competitors do!
Yep -- and it seems to occur extremely rarely. Every university course and
textbook on ecology insists that there is natural selection against
competition because even for the best competitor competition needs more
energy than no competition. This is given as the explanation for why
biodiversity is as high as it is: in order to escape competition, species
specialize into smaller and smaller ecological niches. High biodiversity is
"the ghost of competition past".
Unless you are hardline Etheridgian (one who says that
_all_ species distribution is a result of
past catastrophies and species taking advantage of open niches).
I've never heard of this view, but I don't agree with it. When species
split, their ecological niches usually split with them.
> However, never forget how poor the fossil record of pterosaurs in the LK
> We don't _know_ if _any_ pterosaur clade that is known from the EK went
> extinct before the K-Pg boundary. The most extreme examples are the
> anurognathids: although known from the MJ to the EK, they have to date
> _only_ been found in Konservatlagerstätten. Outside they seem to have
> _no trace_ across some 60 million years!!! I don't know of a LK
This is astonishing, indeed. So, you suspect that pterosaurs were fully
diverse till the end?
I'm pretty certain that we have no reasonable idea whatsoever of how diverse
pterosaurs were at the end -- within some 2 orders of magnitude. This, in
turn, leads me to the conclusion that we can't base a hypothesis about
pterosaur extinction on the known diversity of pterosaurs.
While I am at it, I can turn everything on its head. We can be quite certain
that there were no more pterosaurs in the middle Eocene; Messel, the Green
River Fm and the like would have preserved them. We can also be pretty
certain that the Eocene whale-bearing sediments of much of the world would
have preserved large marine pterosaurs. But the Paleocene... the entire
positive evidence for the absence of pterosaurs in the Paleocene is that
there are plenty of reasons to think that pterosaurs wouldn't have survived
the conditions of the K-Pg boundary impact.