[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Fwd: Removing segnosaurs from Theropoda



Jason Head wrote:
>
>        Only if you're a bad cladist!!  as for circular arguements,
>studying morphological characters that are convergant will lead OF COURSE
>reveal their convergant nature (In the dictionary: for redundant, see
>redundant).  Nobody performing an in-depth analysis of comparative anatomy
>would confuse sharks, ichthyosaurs, and dolphins (not nowadays, anyway).
>Overall, gross convergances between taxa are easily spotable, but the list
>of convergant characters that were previously deemed homologous via apriori
>reasoning is quite long.  Obviously, at a basal level some subjectivity
>comes to play in analysis, it is the nature of the beast.  However,
>deciding that pes structure or possession of interdentary plates is
>convergant between two dinosaur taxa, before phylogenetic analysis, is an
>apriori assumption, that smacks of a desire to see a particular
>relationship instead of a desire to see whatever relationship unfolds in
>the mix.  I say this w/out intending to "flame" anyone in particular, but
>with the future of paleontology in potentially dire straits (a la
>congress/Ralph Reed- told you I'd start talking  about religion and
>politics), we all need to dot our "i"s, cross our "t"s, and perform the
>most scientifically accurate work possible.  This means formulating our
>ideas upon the results of analysis, not shaping analysis to conform to our
>ideas.
>
>        All My Best,
>

Fine James, but blindly scoring characters is no substitute for detailed
morphological analysis in the first place. The idea that "score enough
characters and eventually you will get the right answer" seems to be a
modern analogue of Darwins argument of "split enough rocks and one day you
will find every intermediate stage between amebo and man". It might sound
good but the real world is not that kind. Sure, a good analysis will reveal
homoplasy in a group but that is no reason to ignore possible convergent
characters in the initial morphological study. As for the "bad cladist"
crap, I try to avoid such tautologies (madly refrains from adding
emoticon). Surely it is time to realise that cladistics is only a tool, not
a religion. It does get results, good ones at that, but it should not be
used to the exclusion of other approaches or the application of common
sence.

Cheers, Paul

pwillis@ozemail.com.au