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Re: Declining pterosaur diversity

John Bois (jbois@umd5.umd.edu) wrote:

<Alroy's thing is that nothing important happened until the K/T event;
that this lead to a subsequent radiation of mammals that have the signal
traits of extant mammals.  Crown groups are important to Alroy, no? And
what about me?  I would like a finding of mammals (and birds) that
increase predation/competition pressure over the Cretaceous.  Crown groups
would ne nice but not necessary.>

  Okay, first, there don't appear to be that many fossil representatives
of any mammal crown groups, and only some questionable avian crown groups
have been identified, including an undescribed "loon," etc. A crown clade
does not include its fossil ancestors.

  The point of my identifying this "discussion" as being too brief is that
the only evidence they cited to suggest it, was a contradiction. To
continue with this, I had written:

<< ...the authors support the declining diversity they see as evidence for
this replacement regime. We need more evidence for this, not ghost
competitors to explain a problem with the extinction scenario.>>

Yo which John Bois replied:

<One of the most important functions of a scientist is to propose testable
and alternate hypotheses.  This paper is very much in this spirit.>

  The hypothesis must be based on a phenomenon that can be described, and
having evidence to lead to it. Penny and Phillips did NOT offer any such
evidence, or why this scenario was plausible, rather they just created a
"just-so" story to "refute" other models. While the idea is good to start
on, it's an idea until there can be found support for it. Only then does
one test. There is no such published support for this "K/T Event caused
virtually no conditions contributing to the demise of the pterosaurs and
dinosaurs" idea. If their hypothesis requires a competitive or replacing
models for ecological niches, then where are those replacements for the
dead dinosaurs and large pterosaurs from the Maastrichtian? Saying it
leads to a replacement scenario requires a replacing phenomenon, which is
absent as presented.

  (As a note on dinosaur diversity, I'm sure I can lump five taxa into
one, thereby "proving" dinosaurs were reducing in number. This is how
those who assess dinosaur diversity measure it. Doesn't that sound wierd?)


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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