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Protungulatum index; pterosaur finger.




Bois asked David M. about the spontaneous generation of Paleocene mammals:

> > Did it ride in on
> > the bolide?  Did it fly in from the coast?  It was right there at the
very
> > earliest Puercan 1...
>
> When? 1 Ma after the K-T? 5 Ma?

No, right at the very start--time zero!  Pu2 starts at about 400,000 years
after the K/T; but Protungulatum is there--I believe it's the idex
fossil!--right at the beginning of Pu1.

> > Bois said about pterosaurs:
> > >> Here you may be up against absolute limits in structural design.
Come
> to
> > >> think of it, good reason to go extinct.
> > >
> > > Then please suggest some structural constraints.

Quoting Romer: "It seems obvious that (pterosaurs) were not so well adapted
for (flying) as birds...The pterosaurs appeared first in the field...but, by
Upper Cretaceous times, highly developed flying birds had been evolved;
competition with them may have been a factor in the elimination of the last
of the pterosaurs."

OK.  He was writing before the bolide was discovered.  But his hypothesis
must still be taken seriously.  If he is right about birds' abilities
relative to pterosaurs', the following behaviors should be considered:
- mobbing of larger falconiforms by smaller pterosaurs would be unlikely
because feathers confer greater manueverability to creatures of equal size
(therefore, larger birds could be just as--or more--manueverable as smaller
pterosaurs)
-large flying pterosaurs would be sitting ducks.  Falconiforms drop on them
from on high, etc., etc.
- 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
-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).  This additional PI costs and make pterosaurs
inferior competitors to birds leaving the nest earlier
-birds like caracara hawk perch near nests of larger rhea...rhea can attack
and kill the hawk except that it just flies away...waiting for the rifght
moment it snatches the less agile parent's chick and flies off with
impunity.  Hoplelessly clumsy pterosaur walkers--relative to nimble waiting
fliers, at least--must watch their babies more carefully.  More PI
needed...therefore they are less competitive.

...for starters.