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Re: Phytodinosauria status



If something went out earlier, I'm sorry, it was not my
intention.

Jordan Mallon (j_mallon@hotmail.com) writes:

<<I'm just curious as to whether or not anyone still subscribes
to Bakker's "Phytodinosauria", as mentioned in his _Dinosaur
Heresies?>>

and George Olshevsky (dinogeorge@aol.com) wrote:

<Most dinosaur paleontologists think Saurischia and Ornithischia
are the fundamental dichotomy of Dinosauria, but the 17 or so
characters that supposedly support this seem very equivocal to
me.>

  Which characters and how do they seem equivocal to you? Unlike
traditional taxonomy, the pelvic arrangement is not one of
these.

<Just a little nudging of the cladogram would move Ornithischia
into Saurischia as prosauropod descendants (Prosauropoda is a
paraphyletic group, I think, and may number both ornithischians
and herrerasaurians among its Late Triassic descendants)>

  Prosauropoda probably is paraphyletic, and includes about
three distinct groups: Plateosauria, which is monophyletic and
is strictly defined; *Thecodontosaurus*, which is possibly the
most basal member of Sauropodomorpha; and anchisaurs, which are
between thecodontosaurs and plateosaurs + sauropods. The more
basal forms *Saturnalia* and *Guaibasaurus* seem to show a
radiation of an as yet even more basal
sauropodomorphan/saurischian, and a truly basal saurischian
which seems to be more primitive than herrerasaurus _and_
"prosauropods". Predation seems to be the basal type of tooth
and anatomical specialization, and in this "prosauropods" are
derived in being apparently adapted to herbivory. As a group, or
trend, not a miscellaneous collectiveand well-supported
dichotomy and its present supporting characters.

<closely related to Massospondylidae--which makes a great deal
more sense to me than leaving ornithischians to evolve a lot of
dinosaurian features on their own, independently of
"saurischians.">

Read Novas, 1991, his PhD thesis (I haven't, but it apparently
goes in further detail?), Arcucci, 1989, 1990; and Sereno and
Arcucci, 1993, 1994, for further studies on basal dinosaurs and
their outgroups, especially with tests to dinosaurian monophyly.
Zhao, 1985 (_Acta Palaeontologia Polonica_), tested monophyly in
dinosaurs, as well, in a non-cladisitic fashion, but it is
Arcucci, Novas, and Sereno who've found the essential
characters.

<Then the fundamental dichotomy of Dinosauria would be into
Phytodinosauria (sauropods, prosauropods, ornithischians) and
Aves (herrerasaurians, theropods, and birds). Phytodinosauria
Bakker 1986 was earlier named Ornithischiformes by Michael
Cooper in 1985.>

  I'd like to know what the strict support is for this
arrangement. Greg Paul's 1984 analysis falls apart with
homoplasies, meaning I'd like to see it refined.

  Earlier, you said that prosauropods probably gave rise to
herrerasaurs, yet here you group prosauropods in phytodinosaurs,
and herrerasaurs in avians...

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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