Re: Bainoceratops & other basal neoceratopsians

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

>In a message dated 5/29/03 1:52:55 PM Pacific Daylight Time, 
>qilongia@yahoo.com writes:
>
><< *Chaoyoungsaurus* lacks the "jugal thingie" which I assume is used to
> refer to an apicular lateral and ventral expansion of the lateral jugal. >>
>
>Someone else said Chaoyangsaurus (it's easy to check spelling if you're in 
>doubt; just go to my Dinosaur Genera List and click on C) had a "jugal 
>thingie," 
>which I believe is better known as a "jugal boss" (and I should have called 
>it that originally in this thread). As with so many morphological 
>minifeatures, 
>we have no idea whether this is a true synapomorphy or some kind of 
>homoplasy; we just plug it into our PAUP programs and let them chug away.

I'd have to actually examine the material to be sure, but I would agree that 
_Chaoyangsaurus_ does preserve a jugal boss (=thingy).  The midsection of the 
jugal shows a minor lateral projection, which I believe was referred to as a 
"boss" in the original description of this taxon.  But, this "boss" is quite 
different than the marked dorsoventral projection seen in _Psittacosaurus_ and 
more derived ceratopsians.  Instead, it is more similar to the form seen in 
heterodontosaurs.  

Again, although I would have to get my hands on the original material to even 
start to offer any concrete hypotheses, my preliminary view is that these are 
two different characters: a lateral projection of the jugal (which is a 
synapomorphy of a very inclusive group including heterodontosaurs, 
_Orodromeus_, _Chaoyangsaurus_, _Psittacosaurus_, and other ceratopsians or a 
convergent feature between some of these taxa) and a bona fide, strong 
dorsoventral crest (which is a synapomorphy of _Psittacosaurus_ and 
Neoceratopsia).

Steve  

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Stephen Brusatte
Geophysical Sciences
University of Chicago
Dino Land Paleontology-http://www.geocities.com/stegob
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