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Clade
Subclade

Taxon
Taxon
Ceratopsia
Nominal Author
Marsh 1890
2nd Nominal Author
Taxon Status ACTIVE
Comments
Ceratopsia was defined independently, first by Dodson (1997) and later by Sereno (1998), both authors proposing similar stem-based definitions. The active definition is a first-order revision using species as specifiers and including several additional external specifiers. These extra specifiers insure stability of taxonomic content, given the paucity of data that currently establishes Pachycephalosauria as the immediate outgroup.
Potential Synonomy
Ceratopia (Charig 1979, spelling variant)

Active Phylogenetic Definition
Active Definition
The most inclusive clade including Triceratops horridus Marsh 1889 but not Pachycephalosaurus wyomingensis (Gilmore 1931), Heterodontosaurus tucki Crompton and Charig 1962, Hypsilophodon foxii Huxley 1869, Ankylosaurus magniventris Brown 1908.
Shorthand
> Triceratops horridus but not Pachycephalosaurus wyomingensis, Heterodontosaurus tucki, Hypsilophodon foxii, Ankylosaurus magniventris.
Definitional Author
Sereno 2005
Definition Status checked
Definition Type STEM
Node-Stem Triplet STEM
Other Triplet Taxa
Marginocephalia, Pachycephalosauria
Specifiers
Specifier(s) A
Triceratops horridus
Specifier(s) B
Specifier(s) C
Pachycephalosaurus wyomingensis, Heterodontosaurus tucki, Hypsilophodon foxii, Ankylosaurus magniventris
Qualifiers
+Taxon
-Taxon
Datum
Taxonomic Content
Publication Year Unknown
Unknown
Unknown
1997

Inactive Taxon Status
Rejection Criteria
Critique
 

Definitional History #1
Earliest Record
All Marginocephalia closer to Ceratopsidae than to Pachycephalosauridae.
Latest Record
Dodson 1997:106
Range (My)
Range (My)
Ceratopsidae, Pachycephalosauridae
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Definitional History #2
Earliest Record
All marginocephalians closer to Triceratops than to Pachycephalosaurus.
Latest Record
Sereno 1998:62
Range (My)
Range (My)
Triceratops, Pachycephalosaurus
Range (My)

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