Chapter One
Basal Ceratopsia
YOU HAILU
PETER DODSON
Ceratopsia consists of Psittacosauridae and Neoceratopsia, the
latter formed by numerous basal taxa and Ceratopsidae. Consequently,
this chapter on basal ceratopsians includes psittacosaurids
and nonceratopsid neoceratopsians. Psittacosauridae is
a monogeneric (Psittacosaurus) clade consisting of 10 species,
while basal Neoceratopsia is formed by 11 genera, with 12 species
of basal Neoceratopsia being recognized (table 22.1). Psittacosaurids
are known from the Early Cretaceous of Asia, whereas
basal neoceratopsians come from the latest Jurassic (Chaoyangsaurus
youngi, Zhao et al. 1999; Swisher et al. 2002) to the latest
Cretaceous in Asia and North America. Basal ceratopsians are
small (1-3 m long), bipedal or quadrupedal herbivores (figs.
22.1, 22.2). Several taxa are extremely abundant and are represented
by growth series from hatchlings to adults. Sexual dimorphism
in Protoceratops is well supported (Dodson 1976;
Lambert et al. 2001; Tereshchenko 2001). Basal neoceratopsians
evolved larger skulls relative to their postcranial skeletons and
more developed frills than psittacosaurids.
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