[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Protoceratopsidae's relations
> Within the family Protoceratopsidae, there seem to be two subgroups, the
>Leptoceratopsians (_Leptoceratops_, _Bagaceratops_) and Protoceratopsians
>(_Protoceratops_, Montanaceratops_). The Leptoceratopsians are considered
>more primitive because of their lack of facial horns and smaller frills, and
>therefore closer to Psiticosaurs than are the Protoceratopsians; and the
>Protoceratopsinas more advanced because of facial horns and large frills,
>therefore closer to "Ceratopsids" than are Leptoceratopsians.
> However, the short, "finback" tails that are possessed by both groups
>suggest that neither group is ancesteral to true "Ceratopsids". Question: is
>the family Protoceratopsidae paraphyletic (or polyphyletic, I can never
>remember which) with the Leptoceratopsians closer to Psiticosaurs than the
>are to "Ceratopsids", and the Protoceratopsians closer to "Ceratopsids" than
>they are to Psiticosaurs - with the "Ceratopsid's" lack of the "finback" tail
>seen as a reversion - ; or are Protoceratopsians ancesteral to nothing and
>the features that would seem to link them to "Ceratopsids" just convergent?
You forgot Asiaceratops (not a problem - it is very forgettable) and
Udanoceratops (the most primitive known protoceratopsid).
Dodson & Currie believe that Protoceratopsidae is monophyletic, and thus the
frills in advanced protoceratopsids are convergent with those of
Ceratopsidae. Sereno (and some others) hold that the protoceratopsids are
the paraphyletic sister taxa of Ceratopsidae, with Protoceratops and
Montanaceratops being very close to the ancestors of the ceratopsids.
Take your pick (or find some new characters or taxa to analyse!).
Thomas R. Holtz, Jr.
Dept. of Geology
University of Maryland
College Park, MD 20742