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Steve Brusatte wrote:
<<All over the place in Asia, yes. Mostly northern China and Mongolia, as
Peter
said, but there is also P. sattayaraki from Thailand (which is so
fragmentary...has this one been debunked yet?). However, northern China and
Mongolia, although very, very large, is still the same general area. Now,
we
only need more stratigraphy and temporal data, which is always hard to come
by.>>

Psittacosaurus sattayaraki has not been âdebunked.â I did not include it
because I do not consider it complete enough to be considered a valid
species. The jaw IS from a psittacosaur that is similar to P. mongoliensis
and P. meileyengensis, but in my opinion should have been described just as
Psittacosauridae indet.

Additionally, I think youâre still not understanding the point I was trying
to make.  The very, very large range in Asia that psittacosaurs lived in,
as well as the probably very extensive temporal range that psittacosaurs
lived demonstrates that they didn't all live together and weren't competing
directly.  In fact, you'd be hard pressed to find two species of
Psittacosaurus
that even SAW each other alive, save for P. sinensis and P. youngi.Â
Insisting
that all the various species of Psittacosaurus must be lumped into one or two
is like insisting that all the various fossil equids in North America must be
lumped into one or two equid species because they lived in North America and
lived during the Cenozoic.

About Psittacosaurus youngi being removed from P. sinensis:
<<Well, you wrote above that Sereno considers the two synonymous. What is
different between his analysis and yours? Sereno, in my opinion, is the
world
expert on these guys, so if he said that P. sinesis and P. youngi were one
and
the same, then I would tend to support him. However, I would need to be
able
to study the specimens myself...>>

Granted I have not seen the specimens, so I cannot be 100% sure, but unless
Sereno is illustrating the specimens with massive inaccuracy, theyâre very
different. P. sinensis has absolutely gigantic jugal horns that point
horizontally and nearly double the skull width. Additionally, the rostral
edge of the jugal horns are nearly perpendicular to the skullâs midline.

P. youngi on the other hand does not have the derived horns of P. sinensis.Â
Instead, they are shorter and back-swept like those seen in P. mongoliensis
and P. neimongoliensis. Additionally, the predentary of P youngi is very
short caudorostrally, and very deep dorsoventrally, which is unlike the
condition seen in P. sinensis, or any other psittacosaur except P.
neimongoliensis.

<<However, I still think that six species of Psittacosaurus was an awful
large
amount, especially if they were the same general size and had the same
general
diet.>>

Perhaps if you were to explain WHY you think each of these species should
be sunk, I might be a little more open to the idea. Instead however, you
insist on sinking the species because it doesnât sit well with you that
there was a diversification event that spanned most of the Early Cretaceous
and nearly all of Eastern Asia.

Conversely, perhaps your contention is based on the fact that most other
dinosaurs are generically oversplit. Take hadrosaurids for example: do
Anatotitan and Edmontosaurus really need to be in different genera? Do
Hypacrosaurus, Corythosaurus and Lambeosaurus need to be in different
genera? Probably not for both questions. If psittacosaur species would
have been given different generic names, perhaps this wouldnât be an issue.

<<P. neimongoliensis is very similar to P. mongoliensis, judging by what I
have read. Some of these similarities have been mentioned in previous
posts.
These two may be prime candidates for grouping. However, this is just based
on
my readings and no examination of the specimens whatsoever.>>

This is untrue. P. mongoliensis has a very long skull with a
prominent dentary ridge. P. neimongoliensis on the other hand has a
foreshortened face, lacks the dentary ridge and has a very deep predentary
reminiscent of that seen in P. youngi.

In fact, the only possible specific sinking that I could think of is putting
P. neimongoliensis into P. youngi, as they both have the very deep
predentary and not very prominent, somewhat backswept jugal horns.

The following is a rough âcladogramâ of how I am thinking psittacosaurs
might have diversified:

--+--+--Psittacosaurus mongoliensis
 | |
 | +--P. meileyengensis
 |
 +--+--P. youngi + P. neimongoliensis
 Â |
 Â +--+--P. ordosensis
    |
    +--+--P. sinensis
   Â   |
       +--P. xinjiangensis


As an aside.... The 6.8 earthquake here (Seattle) last week surprisingly
didnât knock over the two large bookshelves in my house, but simply knocked
my shampoo bottles into the bathtub. Anyway... on to psittacosaurs.

Pete Buchholz
tetanurae@aol.com

âI feel fine.â
 ------ âViceâ President Richard âDickâ Cheney