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JEHOLOSAURUS PHYLOGENY



With the help of Mickey Mortimer, I constructed a preliminary phylogenetic
analysis of some basal ornithischian taxa to help me figure out where
Jeholosaurus may fit in.  I still don't know :-)

The analysis had 17 OTUs, 34 characters, and came up with 51 equally
parsimonious trees.  One portion of the tree, came up consistantly:

--+--Hypsilophodon
 +--+--Tenontosaurus dossi
    +--+--Tenontosaurus tilletorum
       +--+--Gaspirinisaura
          +--+--Dryosaurus
             +--ANKYLOPOLLEXIA

The rest of the tree however is pretty unstable, mostly having to do with the
large amount of missing data in Thescelosaurus, which jumped around as 1) the
sister taxon to Thyreophora 2) the sister taxon to Heterodontosauridae +
Marginocephalia 3) the sister taxon to Jeholosaurus 4) the sister taxon to
Agilisaurus 5) the sister taxon to "Y" multidens + Zephyrosaurus 6) the
sister taxon to Euornithopoda and 7) somewhere out in Theropoda (kidding on
that last one).  Hopefully the new skull and skeleton of "Willow" will clear
this up a lot, as more than half of Thescelosaurus' skull data is question
marks.

Mickey and I then re-ran the matrix without Thescelosaurus and came up with
most parsimnonious trees, and a heck of a lot more stability.  The results
consistantly demonstrate that Jeholosaurus is outside of the Ornithopoda.  It
appears to be outside of Agilisaurus + Cerapoda as well, though sometimes
groups as the sister taxon to an exclusive (Agilisaurus (Heterodontosauridae,
Marginocephalia)).

The consensus tree is as follows:

--+--Lesothosaurus
 |--Jeholosaurus
 |--Agilisaurus
 |--THYREOPHORA
 |--+--"Y" multidens
 |  +--Zephyrosaurus
 |--+--HETERODONTOSAURIDAE
 |  +--MARGINOCEPHALIA
 +--+--Hypsilophodon
    +--+--Tenontosaurus dossi
       +--+--T. tilletorum
          +--+--Gaspirinisaura
             +--+--Dryosaurus
                +--ANKYLOPOLLEXIA

But a phylogeny that might be a little closer to the truth is:

--+--Lesothosaurus
 +--+--THYREOPHORA
    +--+--Jeholosaurus
       +--+--Agilisaurus
          +--+--+--HETERODONTOSAURIDAE
             |  +--MARGINOCEPHALIA
             +--+--+--"Y" multidens
                |  +--Zephyrosaurus
                +--+--Hypsilophodon
                   +--+--Tenontosaurus tilletorum
                      +--+--T dossi
                         +--+--Gaspirinisaura
                            +--+--Dryosaurus
                               +--ANKYLOPOLLEXIA

I believe this because many of the characters linking Agilisaurus and
Marginocephalians are likely to be convergences, so the trees favoring
Agilisaurus outside of Cerapoda carry a little more weight in my subjective
mind, see the following for an explanation of Agilisaurus Marginocephalian
convergences:

http://www.cmnh.org/fun/dinosaur-archive/2001Jun/msg00378.html
http://www.cmnh.org/fun/dinosaur-archive/2001Jun/msg00519.html

That's it for now... keep finding these ornithischians, they're super cool
:-)  Much more exciting that theropods any day of the week.

Pete Buchholz
Tetanurae@aol.com