[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: some questions

In a message dated 97-05-08 08:34:18 EDT, th81@umail.umd.edu (Thomas R.
Holtz, Jr.) writes:

<< Well, they are all stegosaurians.  No one has published a phylogenetic
 analysis with an explicit data matrix out there for these guys yet...>>

There's really little point in it, since after going to all that trouble the
cladogram will almost certainly come out pretty much the same as when I
worked it out for the Kyuryugaku Saizensen article. The Weishampel-Fastovsky
cladogram is nearly identical to mine. Stegosaurs wear their characters on
their sleeves; with only 3-4 good skulls known, there's little anatomical
digging around that can be done in that region of the skeleton for cladistic

<< They neglected Regnosaurus (which can be forgiven, as it's stegosaurian
 nature was realized until this book was in press)...>>

Unforgiveable, since I outed _Regnosaurus_ as a stegosaur in the Kyoryugaku
Saizensen article >two years< before Barrett & Upchurch's cladistic study of
the type specimen confirmed it. Unlike Peter Galton, who was convinced by my
descriptions, W&F evidently weren't. I feel like Cassandra sometimes.

<<...and Wuherosaurus (less
 forgiveable!).  Presumably, the former is somewhere near the base of the
 tree (with Huayangosaurus or Dacentrurus) and the latter is at the crown of
 the tree (I am quite favorable to Olshevsky's hypothesis that Wuherosaurus
 and the species of Stegosaurus are sister taxa). >>

Yes, _Regnosaurus_ is a very primitive stegosaur. In the Kyoryugaku Saizensen
article, I put it in the then new family Dacentruridae, just above
Huayangosauridae; Barrett & Upchurch later put it in Huayangosauridae itself.

Likewise, I found _Wuerhosaurus_ to be a very derived form right up there
with _Stegosaurus_ at the crown of Stegosauria.

One stegosaur that everyone else has overlooked (I published this in the
ankylosaur article for Kyoryugaku Saizensen) is _Emausaurus ernsti_, which
shows a number of huayangosaurid stegosaur characters in the skull and
mandible and is in fact the world's oldest and most primitive stegosaurian.
It's >not< a thyreophoran, nor is it an ankylosaur close to _Scelidosaurus_
and _Scutellosaurus_ as many have it. There's at least one relatively large,
flat but spinelike stego plate associated with the type specimen, too.

Finally, Thyreophora is almost certainly diphyletic. Ankylosaurians derive
from much more primitive ornithischians than do the stegosaurians, which are
the sister group of the heterodontosaurians (=heterodontosaurids +
marginocephalians) plus ornithopods. (I can't off the top of my head recall
Sereno's name for the latter clade.)

My revised cladogram (excluding the non-stegosaurian _Dravidosaurus_, which I
had a really difficult time analyzing and now I know why) will appear in
_Historical Dinosaurology_ #1. This year, I hope.