RE: "real" opisthopuby (very speculative)

["Michael de Sosa" <ofsosa@uclink4.berkeley.edu>]

> what was even more interesting was that in this paper the main
> lines of the
> ornithischians are thought ot come from a hypsilophodontian
> "plexus" instead
> of a simple line, with things like iguanodonts beig a grade.
> further more,
> he lists stegosaurs as being completly unrelated to ankylosaurs, and
> actually has stegosaurs, ankylosaurs and the hypsolophidont plexus all
> originating near simulatneously from the pseudosuchian stock.  Of course,
> this is back in 1971, and i just note it as its interesting to
> see how much
> has drastically changed since then, while, say, Ostrom's dromaeosaur idea
> has survived (for nearly as long i think right?).

If you like that, you should see Zhao (1983), which puts dinosaurs into
seven (!) separate lineages originating from "Pseudosuchia"... Sauropoda,
Plateosauria (=Prosauropoda), Coelurosauria, Carnosauria, Armatosauria
(=Thyreophora), Pachycephalosauria (=Marginocephalia), and Ornithopoda.

What I learned from this paper:

1) Sauropods and prosauropods are not related at all. Not even as sister
groups.
2) Ditto for carnosaurs and coelurosaurs.
3) Ornithomimids were the only Late Cretaceous coelurosaurs.
4) Ankylosauria is paraphyletic with respect to stegosaurs.
5) Heterodontosaurs should really be called tianchungosauroids. It makes
sense to rename a group after a recently-named, most poorly known genus
instead of the (second) oldest and most complete genus. Priority schmiority.
6) Heterodontosaurs are basal members of the marginocephalian lineage (hey,
I like this one!)
7) Ceratopsians and pachycephalosaurs are indeed sister groups, but
psittacosaurs are their immediate outgroup.
8) Ornithopods are boring and no matter how funky the rest of the tree gets,
their basic phylogeny never changes.

It is fun to see how science has changed, isn't it?

Ref: Zhao, X.J.  1983.  ?Phylogeny and evolutionary stages of Dinosauria.?
Acta Paleontologica Polonica 28: 295-306.

Mike de Sosa