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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?
--Boycot Taco Bell's "Texas Tacos" and "Border Light" menu items.