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Clade
Subclade

Taxon
Taxon
Thyreophora
Nominal Author
Nopcsa 1915
2nd Nominal Author
Taxon Status ACTIVE
Comments

Thyreophora was first defined by Sereno (1998) as a stem-based taxon, using Ankylosaurus and Triceratops as internal and external specifiers, respectively. Although Nopcsa (1915) originally included ceratopsids (and thus all obligate quadrupedal ornithischians), the taxon has been limited to armored ornithischians ever since the initial cladistic analyses of Ornithischia (Sereno 1986) and was defined in this manner by (Sereno 1998) and by three authors in The Dinosauria (Weishampel et al. 2004).

The active definition is a first-order revision of the original definitionin that uses species as specifiers. It also introduces two external specifiers to stabilize taxonomic content. The additional external specifiers exclude members of other ornithischian clades that otherwise might be included under alternative phylogenetic arrangements.

Note that Cooper (1985:287) appeared to coin a new taxon "Thyreohporina," but he attributed this taxon to Nopcsa (1915). As he did not use Thyreophora elsewhere in his classification, his new taxon is interpreted here as a spelling error meant to refer to Thyreophora. Thyreophorina, in any case, is already in use within Diptera.

Potential Synonomy
Thyreophorina (Cooper 1985, misspelling; preoccupied by a taxon within Diptera)

Active Phylogenetic Definition
Active Definition
The most inclusive clade containing Ankylosaurus magniventris Brown 1908 but not Parasaurolophus walkeri Parks 1922, Pachycephalosaurus wyomingensis (Gilmore 1931), Triceratops horridus Marsh 1889.
Shorthand
> Ankylosaurus magniventris but not Parasaurolophus walkeri, Pachycephalosaurus wyomingensis, Triceratops horridus.
Definitional Author
Sereno 2005
Definition Status checked
Definition Type STEM
Node-Stem Triplet STEM
Other Triplet Taxa
Genasauria, Neornithischia
Specifiers
Specifier(s) A
Ankylosaurus magniventris
Specifier(s) B
Specifier(s) C
Parasaurolophus walkeri, Pachycephalosaurus wyomingensis, Triceratops horridus
Qualifiers
+Taxon
-Taxon
Datum
Taxonomic Content
Publication Year Unknown
Unknown
Unknown
1998

Inactive Taxon Status
Rejection Criteria
Critique
 

Definitional History #1
Earliest Record
All genasaurs closer to Ankylosaurus than to Triceratops.
Latest Record
Sereno 1998:61
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Ankylosaurus, Triceratops
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