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Clade
Subclade Archosauria: Avemetatarsalia to Neornithes 

Taxon Feedback
Taxon Ankylosauria 
Nominal Author Osborn 1923 
2° Nominal Author  
Taxon Status active
inactive
Comments Ankylosauria was independently defined as a stem-based taxon by Carpenter (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). As in Sereno’s (1998) taxonomy, Ankylosauria here is party to a node-stem triplet (with Eurypoda and Stegosauria). 
Potential Synonomy Ancyclosauria (Huene 1914, spelling variant) 

Active Phylogenetic Definition Feedback
Active Definition The most inclusive clade containing Ankylosaurus magniventris Brown 1908 but not Stegosaurus stenops Marsh 1877. 
Shorthand > Ankylosaurus magniventris but not Stegosaurus stenops
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, Stegosauria 
Specifiers
Specifier A Ankylosaurus magniventris 
Specifier(s) B  
Specifier(s) C Stegosaurus stenops 
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 Callovian (165 Ma) 
Latest Record Maastrictian (66 Ma) 
Range (My) 99 
Basis for Range Sarcolestes leedsi from the Callovian of England is the oldest ankylosaur; the youngest are Maastrichtian in age (Vickaryous et al. 2004). Dates are rounded to the nearest million, the earliest from the beginning of the stage and the latest from the end of the stage (Gradstein et al. 2004). 

Definitional History #1
Definition 1 All thyreophoran ornithischians closer to Ankylosaurus than to Stegosaurus
Author Carpenter 1997:16 
Type node  stem 
Specifiers Ankylosaurus, Stegosaurus 
Qualifiers  

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