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Re: New review paper of tyrannosaur paleobiology in Science, with new phylogeny



2010/9/19 Jaime Headden <qi_leong@hotmail.com>:
>
>   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.
>
Forgive me for being ignorant of the literature covering this topic,
but I think the lack of arguments to decide whether a morphological
difference is intraspecific or interspecific is precisely one argument
against the current use of species in paleontology. Something similar
can be said with respect to recognition of differences due to
ontogenetic change vs. intraspecific+interspecific ones. In this
latter case, at least, to determine ontogenetic age of specimens we
have histology (which however should require to infer similar
ontogenetic hystological trajectories via an EPB or something) and
more interestingly (to me at least) from a theoretical point of view,
the parsimony method proposed by Brochu (1996). However, I have seen
the application of that method in few other works. As far as I
understand the method, however, it seems to me that
non-ontogenetically variable characters can be also erroneously
considered as ontogenetically variable, as may occur in a reverse
sense in phylogenetic analyses.

References:
Brochu, C. A. 1996. Closure of neurocentral sutures during crocodilian
ontogeny: implications for maturity assessment in fossil archosaurs.
Journal of Vertebrate Paleontology, 16: 49-62.