The
ceratopsid family also includes the small Protoceratopsids that are
equally distributed in North America and Asia (Dodson, 1996).
Protoceratopsids,
tend to be more rudimentary with respect to their headgear than other
ceratopsids, and presumably include the ancestors of the ceratopsids.
Recently
addmitted into the ceratopsid family was the small
Psittacosaurus from Asia.
Psittacosaurus
is considered to be the primitive, ancestral structure of Ceratopsia.
In fact, this genus is so generalized in its structure that it
doesn't have any horns and
displays only the most meager of frills.
Psittacosaurus
possessed all of the key evolutionary novelties of the Ceratopsia
even though it had only the most basic of frills (Lucas,
1994).
(Sims,
1994) Protoceratops
tends to be
more rudimentary with respect to its headgear than
ceratopsids, and presumably includes the ancestors of the
ceratopsids. (Carnegie
Museum, 1997) Psittacosaurus
is so
generalized in its structure that it doesn't have any
horns
and displays only
the most meager of frills.