Re: dinosaur taxonomy cont.

[pwillis@ozemail.com.au (Paul Willis)]

>The problem as I see it is this.  In order to make comparisons
>between taxonomic groups such as dinosaurs, birds, mammals, etc., I must
>use some taxonomic unit as a basis for comparison.  Let's say I wish to
>compare the body size of dinosaurs with that of extant mammals.  I could
>use the species as a unit of comparison, but many mammal genera have
>multiple species.  This is particularly true among the smaller mammals.  So
>a species-by-species comparison may be heavily biased.  Maybe I should try
>genera.  But if dinosaur genera are mostly monospecific, I'm basically
>comparing dinosaur species to mammal genera.  It is a problem and I suppose
>there is no easy solution.

I'm not sure I understand what you are comparing or why you would want to
do it. In the example you cite, what do you hope to achieve by comparing
body size? By and large, comparisons above the species level are irrelevant
when dealing with extinct animals.

>I take taxonomy above the species level to be about character variation,
>nothing more and nothing less.  This does not make it less "real" than
>species separations.  The two are about different things.  It happens to be
>true that most species show some degree of character differentiation.  But
>the issue of reproductive isolation does not bear on generic distinctions.

Don't sweat on it too much. Any taxonomic determinations above the species
level are essentially arbitary and set by consensus of the workers rather
than any real biological constraints.

>With regard to the issue of credentials, I'm not sure what constitutes
>"scientific" credentials.  I have a Master's Degree in Zoology, but I count
>this an academic credential not a "scientific" one.  In any case, I
>consider appeals to "credentials" to be no different in principle to any
>other ad hominiem attack.  Scientific discourse should in my view address
>the merits of the ideas being proposed, nothing more, nothing less.

Yes and no. I'm not sure how credentials came into this thread but the rule
of thumb is that the more familiarity a worker has with a particular group,
the more respectable their position should be on matters relating to that
group. This usually works but there are notable exceptions of experts whose
opinion isn't worth a pinch of poo and an non expert whose opinions carry
significant weight. Although degree of expertise is not necessarily
correlated to degrees and education, it usually is.

>In my field many papers in peer-reviewed journals cite books, and even
>popular magazines on occasion.  There is no particular effort to determine
>whether a given book is peer reviewed or not.  The content is evaluated by
>each author and each reader.  Nothing is accepted uncritically.

Generally, in taxonomy, peer-reviewed material is given more weight than
other publications because of the historical context that taxonomic
decisions form. There are many cases of taxonomic decisions (above the
species level) being made outside of peer review publication but theses are
largely ignored for the sake of keeping the taxonomic concepts clear.

>If someone has addressed each of the synomomies Greg proposed, on its
>merits, that is enough for me.

But it's probably not enough for the ICZN and that's the rule book the
taxonomists play by.

>Even Greg has no more than 8 species per theropod genus, and the vast
>majority of his genera are monospecific.  One wonders if this is a function
>of the selective fossilization of dinosaurs.  I would be interested in
>hearing any comments on this point.

If you are asking how this would compare to a taxonomy based on a more
complete knowledge based on the theropods being extant and available for
study, we will never know. There are no rules about how many species are
allowed in a genus or how many multiple species genera there will be in a
higher group.


Cheers,

Paul


Dr Paul M.A. Willis
Consulting Vertebrate Palaeontologist
Quinkana Pty Ltd
pwillis@ozemail.com.au

Interesting fact:
Lorne Greene had one of his nipples bitten off by an alligator while he was
host of "Lorne Greene's Wild Kingdom.