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Re: bats



Stephan Pickering (stefanpickering2002@yahoo.com) wrote:

<I think Jaime is mistaken on several levels. One: I think it likely, on
the basis of available molecular data when viewed through the prism of
cladistic analyses of chiropteran phylogeny, that bats (perhaps not as
agile and swift as the Cenozoic forms, but still bats) arose before the
end-Cretaceous.>

  Cladistic analysis does not tell us the timing of divergence, Stephan. I
would like to know where you extrapolated this.

<Not all pterosaurs were extinct by the end of the Cretaceous, and so,>

  Uhm, what pterosaurs were alive by the end of the Cretaceous, pray tell?
I beleive Jim Cunningham is also curious about the answer.

<two: this means sympatric overlapping of population dynamics.>

  Misuse of the term "sympatric", which involves relationship, not
ecology.

<In other words: the feathered dinosaurs, the small pterosaurs, the
proto-bats (I don't know what else to call them) were alive during the
same period, viz. may have co-existed in the same geographical regions.>

  There is no proof for anything you have so far written. All pterosaurs
in the Maastrichtian were fairly large, including Nyctosauridae,
Azhdarchidae, and possibly Pteranodontidae. There is no evidence of bats
in the Maastrichtian, or pterosaurs in the Danian of the Paleocene.
Similarly, the biggest bird in the Cretaceous was terrestrial, as were
other comparative Maastrichtian birds (*Gargantuavis*) though some French,
Romanian, and NA birds were apparently small and flightless, with some
French flighted birds (again, small). This argues there was no comaprative
competitive niches that would have resulted in the dynamic that you,
Stephan, have described.

<There is, admittedly, no evidentiary basis for my supposition, just the
"hunch" that the earliest,>

  Hunches? This is based on hunches, right, and not science? Hasn't this
been my entire point?

<One other thought: Gregory Paul has observed that pterosaurs and bats
share similarities, but with one fundamental difference (as examinations
of skulls demonstrate): bats are bigger-brained. Coupled with being
faster, and able to "out-think" pterosaurs, it could be that our imaginary
end-Cretaceous protobats survived into the Cenozoic for the same reasons
the feathered, flying and secondarily flightless, theropods survived.>

  The discussion by Greg Paul in _Dinosaurs of the Air_ on bats is
essentially true, but his comparisons to pterosaurs and birds are not,
given the arguments revolving around _camber_ (pg. 302; basal birds have
strong camber, essential in the true and waterfowl, and all birds with
"stubby" or rounded wings also have strong camber), tail evolution in bats
(pg. 302; there is no evidence that bats were originally short-tailed, and
in fact all other sister groups [basal archontans like colugos,
scandentians, and primatomorphans] for bats are long tailed, and early
fossil bats also have fairly long tails), arguments over avian speed-based
superiority (pg. 303; basal birds are slower than advanced avian
aerialists, including ducks, turkey, pheasant, etc., and speed adaptations
are based on wing-shape with faster birds occuring within clades, not at
their bases). Pauls' only argument toward pterosaurian and chiropteran
similarity is in the natutre of the wing membrane, but the chiropteran
wing is supported by multiple fingers, versus a single finger in
pterosaurs with actinofibril support. All three animals have differences
in the wing design that cannot be related to one another as easily as
membrane versus non, keels versus non, etc. The wrist and airfoil design
are each unique, as are the shoulders, and assuming similarities must take
these into account, which I have not yet seen. Instead, we are arguing
about assumptions of timing, ecologies that are not in evidence, and so
forth.   

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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