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re: Brusatte et al. 2008



David Peters wrote:

>1. The [theropod + theropod-like forms] form a clade separate from
>[the rest of the dinosaurs + pterosaurs  + 'Crurotarsi.']

Hi David, I'm not seeing this.  Please clarify.

>2. The above-named clades all have the low-slung, low-skull, naris-on-
>top Proterochampsidae as their closest known sister taxon succeeding
>Euparkeria and Erythrosuchus as more distant outgroups.

In the published tree Proterochampsidae is the sister taxon to Archosauria
as is common in many analyses.  Again, I'm not understanding your point.
Please clarify.

Again another interesting tree (a super tree) and character set, but I
think that we are still quite a few studies (and new specimens as well)
away from something meaningful. To be fair, the Brusatte et al. cladogram
was derived as a tool to determine evolutionary rates within clades, NOT to
provide a new phylogeny (this from Steve himself and in the paper).   I'm
looking forward to Steve's next phylogenetic analysis paper (in review) as
well as results of PhD research by Sterling Nesbitt and Randy Irmis (who
are dealing with the pseudosuchian and ornithodiran clades respectively)
which should all add tons of new information.  I'm also hoping that a full
description and coding of Revueltosaurus (in the works) will help polarize
some characters and thus clarify relationships within Pseudosuchia.  LOTS
more to do.

Bill

************************************************************************
Bill Parker
Vertebrate Paleontologist
Division of Resource Management
Petrified Forest National Park
P.O. Box 2217
1 Park Road
Petrified Forest, AZ 86028
(928) 524-6228 x262


|---------+---------------------------->
|         |           David Peters     |
|         |           <davidpeters@att.|
|         |           net>             |
|         |           Sent by:         |
|         |           owner-DINOSAUR@us|
|         |           c.edu            |
|         |                            |
|         |                            |
|         |           09/13/2008 12:32 |
|         |           PM EST           |
|         |           Please respond to|
|         |           davidpeters      |
|---------+---------------------------->
  
>------------------------------------------------------------------------------------------------------------------------------|
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                                                 |
  |       To:       DML list <dinosaur@usc.edu>                                 
                                                 |
  |       cc:       (bcc: William Parker/PEFO/NPS)                              
                                                 |
  |       Subject:  re: Brusatte et al. 2008                                    
                                                 |
  
>------------------------------------------------------------------------------------------------------------------------------|




Having seen the paper and supporting materials, I see that Brusatte
et al. 2008 have a very interesting cladogram.

1. The [theropod + theropod-like forms] form a clade separate from
[the rest of the dinosaurs + pterosaurs  + 'Crurotarsi.']

2. The above-named clades all have the low-slung, low-skull, naris-on-
top Proterochampsidae as their closest known sister taxon succeeding
Euparkeria and Erythrosuchus as more distant outgroups.

3. Scleromochlus, with its teenie-tiny hands and spike like digit V
is the sister taxon to pterosaurs. Sister taxa just outside of this
clade don't have a long manual digit IV or a long pedal digit V
either. In fact, those are hard to find anywhere here [Proterosuchus
is not included]. Was there a miracle in the appearance of wings and
toes? Maybe Hone and Benton can help here.

I know all this represent the traditional paradigm. I've seen
variations on this cladogram many times before, so you won't win
anyone over by tossing in refs that suffer from the same problems.

The big question for you to ponder is this: do all these nestings
make sense in terms of gradualism in evolution? If 'sister taxa'
don't blend morphologically from one to another, isn't that a red flag?

I've written to Steve Brusatte asking for the MacClade file. So
that's step one.

David Peters
davidpeters@att.net