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

Re: Whose definition of Dinosauria?



Thomas R. Holtz, Jr. wrote:
>"Regrettably, it was only later that T.R. Holtz (personal communication)
>suggested that the first two described dinosaurs, Megalosaurus and
>Iguanodon, included in Owen's original Dinosauria, would have been more
>fitting end members than birds and Triceratops!" - p. 178

>Padian, K. 1997.  Dinosauria: Definition.  pp. 175-179.  In Currie, P.J. and
>K. Padian (eds.) Encyclopedia of Dinosaurs.  Academic Press. 
        It seems apparent, at least from the standpoint of dinosaur
systematics, that some measure of review might be in order. Since the rise
of a (more or less)standardized method of phylogenetic taxonomy (generally
through the activities of De Quiroz and Gauthier), there seems to have been
a lot of interest in the idea. However, this seems to have been manifested
mostly in a "rush" to name taxa. This "rush" seems  based on practical
rather than egotistical motives, but has resulted in some controversy (e.g.
crown clades), some poorly thought out applications (e.g. using only
node-based taxa), some consensus (e.g. a general distate for apomorphy-based
taxa), but little synthesis.
        As far as I can see, there are several potentially serious flaws in
how PT is practiced today. Most of these are philosophical rather than
practical, however, if a dippy grad student can see them, I'd be surprised
if the serious practitioners [sic] haven't. Some of these revolve around a
lack of rigorous consideration of the potential results of a definition
(e.g. Def. of Dinosauria); others stem from the fact that just because the
composition of a group *can* change in PT doesn't mean we should define it
without any inherent stability (my oft harped on Dromaeosauridae example).
Others stem from impercision in defintion, or assumption of a particular
phylogeny a priori during definition (not bad, but the consequences must be
accessed). These problems are all interwoven, and it is difficult, even
after a year of considering them on my part, to disentangle the various
components.
        As Dr. Holtz points out above, there are some practical difficulties
which do seem to be widely recognized. Some of these revolve around the
(biologically sound, if not always practical) use of crown clades. Others
revolve around the phylogenetic definition of traditional taxa to reflect
one workers concept of the phylogeny, rather to give the best probability of
continued easy access to the literature.
        PT has had somewhere around a decade to grow (including time before
De Quiroz and Gauthier, when similar practices were followed under different
conditions). It seems that now would be a good time for everybody
(biologists, paleontologists, etc. etc.) to get together and work out the
kinks. Something like one big theoretical meeting, to iron out some of the
kinks (would be kind of fun to do anyway). This could be followed by a
series of smaller meetings, organized roughly by clade, which would have
"plenary powers" (perhaps refereed by a panel of acceptable
mediators(!?!?!)) to reorganize definitions with prioirty suspended, and set
them finally in stone. A referee committee could then be elected, perhaps
equably amongst clades, to judge future disputes (under specified criteria:
e.g. demonstrable possibility of paraphyly inherent in definition [which
does seem possible], potential loss of access to literature, unclear
defintion, etc.). After such a series of meetings, priority could be
reinstated as of the end date of the conference, with further difficulties
moderated by the elected referees.
        While this seems like a rather unprecedented step, both in the
concept of a conference to decide the future of taxonomy, and in the
possibility of wide-scale supression of priority. On the other hand, how
often do we see revolutions in science which are this broad in scope, narrow
in focus, contentious, yet nitpicky and somewhat arbitrary? 

        Wagner

        "Arthur... monkey from nowhere!" - The Tick
----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
        "Chimp here does the killing." - Doug Mackenzie