 The clade Neoceratopsia includes all ceratopsians more derived than <unk> . Another subset of <unk> is called <unk> , which currently includes all ceratopsians more derived than Auroraceratops . <unk> show the first development of the neck frill and the fusion of the first several neck vertebrae to support the increasingly heavy head . Within <unk> , 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 <unk> . 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 <unk> and <unk> ( also known as <unk> ) . 
