RE: Megalosaurids

["Steve Brusatte" <dinoland@lycos.com>]

On Tue, 23 Jul 2002 10:40:33  
 Thomas R. Holtz, Jr. wrote:
>Greetings, everyone,
>
>I'm back from an education conference in Vermont, and have seen many
>interesting things pop up on the list!  I'm VERY VERY VERY happy to see that
>the spiky _Psittacosaurus_ sp. (so noted as the skull is exposed primarily
>in ventral view, so the specific diagnostic characters are not easily
>visible) has been published.

Interesting...I didn't know the skull was in damned ventral view.  However, 
there are some psittacosaurid diagnostic characters that are not related to the 
skull or should be visible in ventral view.  For instance, _P. xinjiangensis_ 
is diagnosed by an elongate postacetabular process of the ilium and the 
posterior expansion of ossified epaxial tendons onto the anterior half of the 
tail.  (It is also diagnosed by a tooth character-maxillary crowns with 
denticulate margin curving posteromedially onto the side near the crown 
base-but I'm cautious with tooth characters in this genus).  _P. 
meileyingensis_ is diagnosed by its unique ventral dentary flange, which can be 
seen in ventral views of its skull.  _P. neimongoliensis_ has an ischium that 
is much longer than the femur, and is also diagnosed by an ischium with a 
distal end that is not horizontally flattened.  

The skull must be preserved so badly in the bristled specimen, or, perhaps it 
displays an odd suite of characters found in other species while at the same 
time displaying few or no true apomorphies.  I'll have to get this paper and 
look at the figures to perhaps deduce more.

And, yes, I second the excitement of seeing this thing published.  Now we can 
talk about it more freely.

Steve

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Steve Brusatte-DINO LAND PALEONTOLOGY
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