[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
They haven't been. We still get long monographs (Clarke's on Ichthyornis,
Chure's upcoming on Allosaurus, etc.),
To be fair, Chure's has been upcoming for years. How old is his thesis? --
In that thesis he describes a complete skeleton (with furcula, gastralia,
and apparently everything else you might wish for) as the holotype of the
new species *Allosaurus jimmadseni*, we all know it, and we're all not even
allowed to use the name. It's not validly published.
and short papers existed in the past
too (ever seen any original descriptions by Marsh?).
Or Cope, for that matter. Horrible. Typically, it seems, a few small pages
of pure text where 3 vertebrae are "described" as 2 new taxa. "Pure text" as
in "no illustration whatsoever".
From your description of the labile nature of current results, it should
clear identifying basic evolutionary patterns is NOT complete. Most
published morphological cladistic analyses are crap. Too few characters
taxa, too subjectively defined states.
The same applies to most, or perhaps all, molecular analyses published
before 2001... and to several younger ones as well. The main reason is
painfully obvious -- computers would have needed months (or would simply
have crashed) trying to process today's matrices.
You change some assumptions in Hutchinson's running model,
and come up with completely different results. ;)
Yes, the elasticity of the tendons is probably an example... :o)
Human thought is inferior to PAUP when it comes to calculating most
parsimonious trees in a realistic time.
In fact, most of classical guesswork at phylogenetic trees is parsimony with
one character, or two, or five. Typically supported by ideology like "in
Carnivora only the braincase is phylogenetically informative, because it
isn't subject to adaptive pressures apart from some stabilizing selection".*
I have seen computer-free cladistics, however. Ax's recent three-volume book
on systematic zoology is an example. It simply uses very few taxa and very
few characters. Consequently, the results are very unreliable. Take the
place where he explains why he thinks Articulata is monophyletic -- most of
the characters there are of doubtful primary homology, and IIRC not a single
proposed morphological synapomorphy of Ecdysozoa even gets considered.
For 9 taxa there are 135135 possible unrooted trees without polytomies.
Almost regardless of the number of characters, it takes PAUP* less than a
second to find out which of those are most parsimonious _in an exhaustive
search_. Try to do that by hand. You will then understand why Hennig
preached (and computer-free cladists still follow it) that the direction of
phylogenetic reconstruction is opposite to that of cladogenesis** -- we are
supposed to take one taxon and look for its sistergroup, then look for the
sistergroup of the clade composed of the first two, and so on. It goes
without saying that this approach routinely fails to take the real sister
taxa into consideration.
* Which of course doesn't mean that the braincase is immune to _random_
convergence -- but people used to simply overlook that. However, the
probability that the braincases will converge _in the same direction_ as the
jaws and forelimbs and necks and whatnot is probably quite low -- and
therefore ALL of those characters and more should be used, instead of
declaring 90 % of them irrelevant.
** Which Hennig called speciation, trying to solve the species problem by
Okay, it technically does include a page of comparison with some
other theropods, but you get the idea.
And I'd rather have that than unresolvable 'which
character is more important' debates any day.
See above. Braincase! Braincase! ;-)
- RE: Resending
- From: Michael Mortimer <email@example.com>