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

Re: worrying decline



>Chris Brochu wrote:
>
>"The trend I'm seeing is toward morphological cladistic analyses that
>rely on museum collections rather than the (untrustworthy) literature"
>
>  I agree with that, in principle. But something keeps worrying me.
>  If it is accepted a priori that no morphological information can be
>gathered from primary descriptions in the literature, what is the point
>of producing such works at all?
>  It is well known that primary descriptions are long lasting pieces of
>work (some more reliable than others, but well), while phylogenetic
>analysis are (and should be) temporary.
>  Therefore, under this point of view - with primary descriptions viewed
>as not precise useless stuff, and phylogenetic analysis so trendy
>nowadays - I am afraid that we will soon stop seen the primary data
>printed (what is already sometimes the case), having instead only
>hypothesis that are to be modified next week.
>



There are different levels of unreliability in the literature.  Some papers
are unreliable for the obvious reason - the person/people who wrote them
did a poor job.  Any systematist can name one or more people who have
worked on their group who fall/fell into this category frequently.

But more common are ambiguities caused by different norms of practice over
time.  In the past, for example, it was considered perfectly acceptable to
figure a restored fossil, with little attention paid to what was real and
what was not.  And some of these restorations were very, very good - one
has to get really close to tell the difference between bone and plaster.
Anyone who's gotten a close look at "Nanotyrannus" knows what I mean.
Coding from the figures and not from the specimen, one might get the
impression that the fossil is more complete than it actually is; and since
the restoration was often driven by the set of relationships favored by the
restorer, there will be a bias toward "features" that may not pertain to
close relatives as currently understood.

Older descriptions often figured just one specimen (or an idealized drawing
thereof), which could give one the impression of morphological uniformity
when a feature is actually quite variable in the museum-curated sample,
most of which was not figured or discussed in the literature.  THis may not
be a really fair criticism of older work, because the technology available
for quality photo reproduction is much better now than it was 100 years ago.

Different aspects of morphology have gotten different levels of emphasis
over time.  Anyone who's tried to look at archosaur braincases from
literature descriptions knows what I mean - these were not always described
as completely as other parts of the skull.  And the postcranium often got
very brief attention (if any attention at all, and if it was even collected
in the first place).

This isn't really a criticism of our predecessors - after all, how could
Richard Owen have known that the sutural relationships on the inside of the
croc Meckelian fossa would be important to some Late-20th-century loser
like myself?  I'm sure someone will come along in a few years and (in
writing!) give me a new blastopore for having ignored some significant
aspect of morphology.  This is why I will never publish on any fossil not
bound for a museum collection (and why I encourage all of my colleagues to
adopt the same policy) - I don't want people relying on me, but on the
fossil, and the fossil MUST be available to future generations.

I don't like to think about the unreliability of the literature; but my
experience with two prominent groups of archosaurs forces me to accept it.
The literature is a great place to start, but I would be very, very
skeptical of any taxonomic revision that did not include first-hand
examination of the actual material.



chris

_________________________
Christopher A. Brochu
Department of Geology
Field Museum
1400 S. Lake Shore Drive
Chicago IL 60605

312-665-7633 voice
312-665-7641 fax
cbrochu@fieldmuseum.org