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RE: The head of Arthurdactylus?




> -----Original Message-----
> From: David Peters [mailto:davidrpeters@earthlink.net]
> Sent: Tuesday, February 11, 2003 9:29 PM
> To: dinosaur list
> Subject: The head of Arthurdactylus?
>
>
> Well, here's what a cladogram can do:
>
> I've matched 60 pterosaur taxa against 170 characters and PAUP came up
> with a single tree. One of the interesting things to emerge was this:
>
> Cearadactylus, known only from a skull sans cranium, came out as the
> sister taxon to Arthurdactylus, known only from post-crania.
>
> I don't know whether to smile or scratch my head.
>
> Did PAUP put them together because they were the last two "wallflowers
> "in the clade? Or is this PAUP at its very best? Has this happened
> elsewhere on the family tree of tetrapods?

Hmmm...  When I see something like that result, I go back and double check
to make sure I didn't mistype a cell (which happens at least once or twice
per matrix).  My suspicion is that there is a single shared character that
is uniting them.

Otherwise, it isn't odd per se to get a head and a postcranium forming a
trichotomy with a third clade, if the head shares characters otherwise found
with that third clade and the postcranium similarly shares characters
otherwise found with that third clade.

If you have MacClade (or you want to use the various character diagnostic
search tools in PAUP), find out what character state change occurs at the
node uniting Ceara. and Arthur.  That is your culprit.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796>