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Re: Phytodinosauria status
In a message dated 6/18/01 2:06:50 AM EST, Adam.Yates@bristol.ac.uk writes:
<< Just a word about the pendant fourth trochanter in Massospondylus. George
has used it as a possible synapomorphy between the Ornithischia and
Massospondylidae but it is only present in one individual of Massospondylus!
There are dozens of other femora all of which have the typical non-pendant
shape. No other members of the Massospondylidae have one either (I include
Lufengosaurus, Yunnanosaurus, Jinshanosaurus and probably Coloradisaurus -
there is an undescribed postcranial skeleton of this guy). I think that the
one specimen that does have it is a pathologic individual (a bony lump
growing on the ventral corner of the 4th trochanter perhaps where the
caudofemoralis had been torn off at some point in its life). >>
I got the impression that Cooper had more than this, but unfortunately my
copy of his big paper is buried and I can't check it. If this is true, then
certainly that pendant massospondylid fourth trochanter is pathological and
taxonomically useless. But I think he may have used this character when he
set up Ornithischiformes. It has been years since I've looked at this stuff.
On another track, I think Massospondylidae right now includes only
Massospondylus. Lufengosaurus and Coloradisaurus are good plateosaurids, not
massospondylids; and Yunnanosaurus and Jingshanosaurus are good
yunnanosaurids. So if they didn't have pendant 4th trochanters, it's not
particularly relevant. I wouldn't consider ornithischians and plateosaurids
or yunnanosaurids particularly closely related.