 The clade Neoceratopsia includes all ceratopsians more derived than psittacosaurids . Another subset of neoceratopsians is called Coronosauria , which currently includes all ceratopsians more derived than Auroraceratops . Coronosaurs show the first development of the neck frill and the fusion of the first several neck vertebrae to support the increasingly heavy head . Within Coronosauria , three groups are generally recognized , although the membership of these groups varies somewhat from study to study and some animals may not fit in any of them . One group can be called Protoceratopsidae and includes Protoceratops and its closest relatives , all Asian . Another group , Leptoceratopsidae , includes mostly North American animals that are more closely related to Leptoceratops . The Ceratopsoidea includes animals like Zuniceratops , which are more closely related to the family Ceratopsidae . This last family includes Triceratops and all the large North American ceratopsians and is further divided into the subfamilies Centrosaurinae and Ceratopsinae ( also known as Chasmosaurinae ) . 
 The clade Neoceratopsia <a href='uninflect' title='1'><mark>includes</mark></a> all ceratopsians more derived than psittacosaurids . Another subset of neoceratopsians is called Coronosauria , which currently <a href='uninflect' title='2'><mark>includes</mark></a> all ceratopsians more derived than Auroraceratops . Coronosaurs show the first development of the neck frill and the fusion of the first several neck vertebrae to support the increasingly heavy head . Within Coronosauria , three groups are generally recognized , although the membership of these groups <a href='uninflect' title='3'><mark>varies</mark></a> somewhat from study to study and some animals may not fit in any of them . One group can be called Protoceratopsidae and <a href='uninflect' title='4'><mark>includes</mark></a> Protoceratops and its closest relatives , all Asian . Another group , Leptoceratopsidae , <a href='uninflect' title='5'><mark>includes</mark></a> mostly North American animals <a href='null_relcl' title='6'><mark>that</mark></a><a href='drop_aux' title='7'><mark>are</mark></a>more closely related to Leptoceratops . The Ceratopsoidea <a href='uninflect' title='8'><mark>includes</mark></a> animals like Zuniceratops , which <a href='drop_aux' title='9'><mark>are</mark></a>more closely related to the family Ceratopsidae . This last family <a href='uninflect' title='10'><mark>includes</mark></a> Triceratops and all the large North American ceratopsians and is further divided into the subfamilies Centrosaurinae and Ceratopsinae ( also known as Chasmosaurinae ) . 
Da clade Neoceratopsia include alll ceratopsians more derived than psittacosaurids . anotha subset of neoceratopsians is called Coronosauria , which currently include all ceratopsians more derived than Auroraceratops . Coronosaurs show the first development of the neck frill and tdafusion of the first several neck vertebrae to support thdancreasingly heavy head . Within Coronosauria , three groups r generally recognized , although thedambership of these groups vary somewhat from study to study and some animals may not fit in any of them . One group can be called Protoceratopsidae and include Protoceratops and its closest relatives , all Asian . Another group , Leptoceratopsidae , include mostly North American animals more closely related to Leptoceratops . The Ceratopsoidea include animals like Zuniceratops , which more closely related to the family Ceratopsidae . This last fam include Triceratops andallll the daass North American ceratopsians and is further divided into the sdaamilies Centrosaurinae and Ceratopsinae ( also known as Chasmosaurinae ) .