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Re: Cladograms
Anthony Chiu (theanthonychiu@hotmail.com) wrote:
<I've been doing some research into two pretty-good dinosaur cladograms.
However, i don't know if there are any others that are better, or as
respectable. I'm talking about Sereno et al (1999) and the Keesey one
(dinosauricon).>
A complete systematic analysis of Dinosauria has yet to be performed.
The most complete analyis, Sereno 1999, was in actuality 6 separate
analyses that was conjoined based on common taxa. The analysis of the
Dinosauricon, not to step on Mike Keesey's toes, is an amalgam of lots of
cladograms and some guesses, as many taxa included have never been run in
an analysis yet. In exception to this, a total analysis would contain over
500+ taxa, over 2,000 characters, and probably take weeks to run on the
computer. Basal dinosaurian taxa, such as analyses run by Novas in the
early 90's and by Gauthier in 1986 (published from a 1984 thesis), have
been superceeded by those today and are no longer consistent in both
characters, and taxa. Benton (1999), ran an analysis using some basal
dinosaurs, pterosaurs, and *Scleromochlus* with the intent to determine
arrangement of taxa, and this suggested what has pretty much been known
before, about the basal arrangement of dinosaurian groups, Sauropodomorpha
+ Theropoda = Saurischia, and Saurischia + Ornithischia = Dinosauria, with
successive outgroups *Pseudolagosuchus,* *Marasuchus,* and *Lagerpeton.*
With the discovery of *Silesaurus,* either a basal dinosaur, basal
ornithischian or --- most likely in my observation --- non-dinosaur
closely-related to the origin of dinosaurs. This would have ramifications
on the distribution of characters and order of some taxa, and has yet to
be seriously tested. Both Langer (2002) and Yates (2002, 2003) have
performed basal saurischian and sauropodomorphan analyses that are
reshaping the order of taxa, so that now, *Anchisaurus* may be a sauropod,
and many other taxa are arranged in groups outside of Sauropoda, and
Wilson and Sereno (2000) and Wilson and Upchurch (2001) have performed the
most concise analysis of sauropods, largely resulting in various
placements for *Omeisaurus,* *Shunosaurus,* and titanosaurs. Sereno (1986)
and (1999) performed the most in-depth analysis of Ornithischia, but this
has been superceeded by new analyses and theories on ornithopod and
marginocephalian species. Holtz (1999, 2000, and 2001) has performed the
most in depth analysis of theropods to date, including over a hundred taxa
and 300+ characters, but this is being reshaped by newer discoveries.
Rauhut (2002) published his thesis and it's characters and taxa are
largely different than Holtz' but the results are largely unique, and
similar to those of Allain (2001) in revising basal tetanuran
relationships. Maniraptoran taxa have received the most attention,
especially in the last few years, with extensive analyses from Xu et al.
(2000, 2001) and Hwang (2002, 2004).
Cheers,
=====
Jaime A. Headden
Little steps are often the hardest to take. We are too used to making leaps
in the face of adversity, that a simple skip is so hard to do. We should all
learn to walk soft, walk small, see the world around us rather than zoom by it.
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
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- References:
- Cladograms
- From: "Anthony Chiu" <theanthonychiu@hotmail.com>