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RE: New review paper of tyrannosaur paleobiology in Science, with new phylogeny
You know what? Yes. You can essentially determine almost ANYTHING to be
"individual variation," or "likely" to be such, or just "ontogenetic," and
dismiss it; or instead determine that such features must automatically be such
as they would seem to be so in some taxon. For the most part, this is little
debated, because sample sizes are either low or artificially composed. I've
talked about the latter (a form of confirmation bias) when it comes to some
authors subjectively assembling a series, and then saying "hey, look! an
ontogenetic series!" without any such thing as a derived sense of understanding
about how to verify this in the first place.
We can say they may be wrong, but we, too, are subject to verification. But
no matter, the next study will have to assess the varification for a premise
that did little to assess its own hypothesis in the first place; or, as
commercial customers say "I'm job security!" There will always be work for
further studies to test previous ones ... but I'd rather those "to be tested"
studies not come from a small group of people, as they tend to. You guys are
all smarter than that, try to show it.
If *Alioramus remotus* is a juvenile or subadult, it may be justifiable to
doubt characterizing it. But based on the data, juvenile *Tarbosaurus bataar*
(from the Nemegt Formation and associated with adults), show more rounded,
robust, and blunter cranial proportions than does *Alioramus remotus*, implying
different yet similar ontogenetic trajectory or conditions at a similar size.
This may relate to differential final growth, faster rates in some, more
paedomorphic trends in another, but that would be justification for separation,
wouldn't it? That's generally why I've sided with Thom Carr and Steve Brusatte
on this issue (regarding the ontogeny) without siding with them on the
taxonomic issue (I would need to see more data).
Jaime A. Headden
The Bite Stuff (site v2)
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion
> Date: Sat, 18 Sep 2010 17:27:20 -0600
> From: firstname.lastname@example.org
> To: email@example.com
> Subject: RE: New review paper of tyrannosaur paleobiology in Science, with
> new phylogeny
> On Thu, 16 Sep 2010, Jaime Headden wrote:
> > ...
> > However, I think it is possible, if not likely, that some taxa can
> > have ontogenetically "juvenile" features while still being adult
> > (paedomorphism). When it comes to generally "juvenile" skeletal and
> > proportionate features in otherwise fundamentally "adult" skeletons that
> > exhibit various other "adult," proportional or ossification trends, one
> > may be permitted the ability to assume or propose a slight paedomorphic
> > trend. Note, for example, that *Xiongguanlong* has an enormously slender
> > and elongate skull, large rounded orbit, and extremely elongate
> > preorbital skull, and large skull relative to its body, but is
> > nonetheless not apparently a juvenile. There should be no constraint
> > that a juvenile morphology should suppress any and all conclusions
> > toward a more mature status, especially given the meagre study so far
> > produced for the taxa presented.
> Couldn't some of this just be considered as individual variation?