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Re:Ceratopsid Question



----- Original Message -----
From: "T. Michael Keesey" <mightyodinn@yahoo.com>
To: "Alessandro Marisa" <amaris@tin.it>
Sent: Monday, March 25, 2002 9:30 PM
Subject: Re:Ceratopsid Question

> >Alessandro Marisa <amaris@tin.it> wrote:
> > The above mentioned genera are not Ceratopsidae, but basal NeoCeratopsia,
> > infact, Protoceratops andrewsi, Bagaceratops rozhdestvensky, Breviceratops
> > kozlowskii, and Microceratops  gobiensis (Graciliceratops mongoliensis (sensu
> > Sereno 2000))  form the Protoceratopsidae (sensu stricto), while
> > Udanoceratops tschizhovi is a member of the Leptoceratopsidae.
 
> I thought _Microceratops_ was more primitive than _Protoceratopsidae_ sensu
> stricto.
You is right if you take a look at the P.J. Makovicky 2001 analysis of basal Ceratopsian pubblished in "Vertebrate Mesozoic Life": Microceratops+(Protoceratops+Bagaceratops) in which Microceratops and Coronosauria shared squamosal T-shaped with a postquadratic process, temporal bars of squamosal posteriorly divergent, and frill fenestrated near posterior margin. But if you take a look at the P. Sereno 2000 analysis of basal Ceratopsian published in "The Age of Dinosaur in Russia and Mongolia" we can see that Protoceratopsidae included Graciliceratops mongoliensis, Protoceratops andrewsi and Bagaceratops rozhdestvenskyi that share three synapomorphies, a narrow strap-shaped paroccipital process, very small occipital condyle, and upturned dorsal margin of the predentary. I think that the position of Microceratops gobiensis within the basal NeoCeratopsian is based on  what do you think is the diagnostic material of Microceratops gobiensis, for example, Sereno in his 2000 analysis considered the HoloType of Microceratops gobiensis (Bohlin 1953) and the second species Microceratops sulcidens as a nomen dubia, and placed ZPAL MgD-I/156 referred to Microceratops gobiensis by Maryanska and Osmolska (1975) in a new genus and species Graciliceratops mongoliensis. In the new P.J. Makovicky (2002) analysis of Liaoceratops yanzigouensis is conding Graciliceratops gobiensis based on ZPAL MgD-I/156 which can be distinguished from other NeoCeratopsian based on differential diagnosed, but not autapomorphy.
The same thing could be applied to Breviceratops kozlowskii, only Chinnery and  Weishampel (1998) analysis of Montanoceratops cerorhynchus used this taxon, P. Sereno (2000) and P.J. Makovicky (2001, 2002) synonymized Breviceratops kozlowskii with other NeoCeratopsian (Makovicky 2002) and with Bagaceratops rozhdestvenskyi (Sereno 2000).
 
By
Alessandro Marisa