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Re: Brrr, bone chilling paleopolar summers(Polar dinosaur growth and other new papers)



2011/8/8 Jaime Headden <qi_leong@hotmail.com>:
>
>   But that's my point. I'm not saying that the reptiles (however narrow that 
> concept seems to me now, and it should) could not migrate, but that migration 
> if it were applied from the mammalian type to the reptilian would involve 
> necessary signatures: We should find similar arctic to subarctic patterns in 
> reptiles as in mammals.
>   Do they exist?

The example of Dermochelys migrating was not put forward to indicate
metabolic similarity between mammals and reptiles. It seems not
sequitur that a similar response, as migration in this case, indicates
a similar metabolism (although it may indicate similarity in activity,
at least that required for migrating), as in the example of
Dermochelys, for it has quite a lower resting metabolism than mammals.
I put forward that example because of being under the impression that
you suggested Gregory Paul required to hypothesize a similar
metabolism for Mesozoic marine reptiles and mammals to dismiss the
evidence from Mesozoic marine reptiles in northern latitudes, while he
was supporting no ectotherm reaches the northern slope.

>    I am also certain that the hot air I spew here is tempered by the fact of 
> missing information: we are not so fully well-sampled that we can make such 
> bald assertions without being vulnerable to attack... Greg Paul is relying on 
> the fact that we lack the distribution of fossils to assert that we are 
> correctly sampling the fauna in order to constrain our theories to fit. This 
> is easily assailable because it's reflected by sampling biases. Supporting a 
> sampling vacuum as a reflection of the real faunal record does us no good.
>
I do not agree too much. While you are right that his hypotheses may
not be true, we always base our hypothesis on the information
currently available, do not wait till all the information possible is
available to reconstruct the more likely scenarios. So knowledge is
perfectible, yes, but thanks to this, we can use our recently
generated theorization (if logical) for application, or, more
basically, to test. If scientists find only a skull, they start
theorizing about its phylogenetic relationships, instead of waiting
until the rest of the skeleton is found to be sure it does not
contradict (which it may conceivably do) the relationships they
inferred from the skull. After all, most of our phylogenetic
hypotheses can turn out to be wrong when new specimens (thus
information) appears or when some brilliant dude recognizes new
characters. Even functional hypotheses may conceivably be challenged
by new information. I do not think either that we need to hypothesize
the sampling is enough to propose hypotheses: how would we be sure
sampling is enough, if conceivably we may never know the actual
original diversity of an ecosystem now associated in a fossil site?
What we are left with, in my view, is that Gregory Paul's hypothesis
of faunal composition is the one requiring less ad-hoc hypotheses
(hypotheses of presence of taxa) and thus, the most parsimonious, even
if not certain, and thus, should be the most favoured.