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Clade
Subclade Archosauria: Avemetatarsalia to Neornithes 

Taxon Feedback
Taxon Stegosauria 
Nominal Author Marsh 1877 
2° Nominal Author  
Taxon Status active
inactive
Comments Stegosauria was independently defined as a stem-based taxon by Galton (1997) and Sereno (1998) using textual variants of the same definition with the same genera as specifiers (Stegosaurus, Ankylosaurus). The active definition is a first-order revision of these initial definitions that uses species as specifiers (Stegosaurus stenops, Ankylosaurus magniventris).  
Potential Synonomy  

Active Phylogenetic Definition Feedback
Active Definition The most inclusive clade containing Stegosaurus stenops Marsh 1877 but not Ankylosaurus magniventris Brown 1908. 
Shorthand > Stegosaurus stenops but not Ankylosaurus magniventris
Definitional Author Sereno 2005 
Definition Status original
textual substitution
first-order revision
second-order revision
Definition Type node
stem
Node-Stem Triplet yes
no
Other Triplet Taxa Eurypoda, Ankylosauria 
Specifiers
Specifier A Stegosaurus stenops 
Specifier(s) B  
Specifier(s) C Ankylosaurus magniventris 
Qualifiers
+Taxon  
-Taxon  
Datum  
Taxonomic Content stem (entirely extinct)
crown (extant-bounded)
mixed (extant/extinct-bounded)
Publication Year 1997 

Inactive Taxon Status Feedback
Rejection Criteria junior synonym
historically polyphyletic
incomplete definition
no definition
apomorphy-based
redundant
other 
Critique  
 

Current Age Range Feedback
Earliest Record Bathonian-Callovian (165 Ma) 
Latest Record Valanginian-Aptian (120 Ma) 
Range (My) 45 
Basis for Range The earliest record is the basal stegosaur Huayangosaurus taibaii from China and the latest is Wuerhosaurus homheni from Valanginian-Aptian-age Tugulu Group in Xinjiang, China (Galton and Upchurch 2004)The fragmentary Dravidosaurus blanfordi from Coniacian-age beds in India is the only record of stegosaurs from the Late Cretaceous, but its identification as a stegosaur has been questioned (Chatterjee and Rudma 1996). Dates are rounded to the nearest million, the earliest at the boundary between the two cited stages and the latest from the midpoint of the stage range indicated (Gradstein et al. 2004). 

Definitional History #1
Definition 1 All thyreophoran ornithischians closer to Stegosaurus than to Ankylosaurus
Author Galton 1997:701 
Type node  stem 
Specifiers Stegosaurus, Ankylosaurus 
Qualifiers  

Definitional History #2
Definition 2 All eurypods closer to Stegosaurus than to Ankylosaurus
Author Sereno 1998:61 
Type node  stem 
Specifiers Stegosaurus, Ankylosaurus 
Qualifiers  

Definitional History #3
Definition 3 All taxa more closely related to Stegosaurus than to Ankylosauria. 
Author Galton and Upchurch 2004:343 
Type node  stem 
Specifiers Stegosaurus, Ankylosauria 
Qualifiers