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Clade
Subclade

Taxon
Taxon
Heterodontosauridae
Nominal Author
Romer 1966
2nd Nominal Author
Taxon Status ACTIVE
Comments

This taxon was originally coined by Romer (1966), which constitutes a well defined monophyletic clade, including Echinodon (Sereno 1997, Norman and Barrett 2002) but very probably excluding the poorly known Pisanosaurus (Butler 2005). Although Heterodontosauridae has been placed inside Ornithopoda as a sister taxon to Euornithopoda, other positions have been entertained, such as outside euornithopods plus marginocephalians (Butler 2005) or near a subclade of marginocephalians (Cooper 1985). The alternattives are not overwhelmingly supported by character evidence.

Given that Heterodontosauridae has a stem-based definition so that it will include newfound basal mambers, several external specifiers are also incorporated in the definition—one from all of the clades that have been forwarded as possible sister taxa. in this way, its traditional taxxonomic content will be maintained under alternative phylogenetic arrangements.

Potential Synonomy
Heterodontosauria

Active Phylogenetic Definition
Active Definition
The most inclusive clade containing Heterodontosaurus tucki Crompton and Charig 1962 but not Parasaurolophus walkeri Parks 1922, Pachycephalosaurus wyomingensis (Gilmore 1931), Triceratops horridus Marsh 1889, Ankylosaurus magniventris Brown 1908.
Shorthand
> Heterodontosaurus tucki but not Parasaurolophus walkeri, Pachycephalosaurus wyomingensis, Triceratops horridus, Ankylosaurus magniventris.
Definitional Author
Sereno 2005
Definition Status checked
Definition Type STEM
Node-Stem Triplet STEM
Other Triplet Taxa
Ornithopoda, Euornithopoda
Specifiers
Specifier(s) A
Heterodontosaurus tucki
Specifier(s) B
Specifier(s) C
Parasaurolophus walkeri, Pachycephalosaurus wyomingensis, Triceratops horridus, Ankylosaurus magni
Qualifiers
+Taxon
-Taxon
Datum
Taxonomic Content
Publication Year Unknown
Unknown
Unknown
1998

Inactive Taxon Status
Rejection Criteria
Critique
 

Definitional History #1
Earliest Record
All ornithopods closer to Heterodontosaurus than to Parasaurolophus.
Latest Record
Sereno 1998:61
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Heterodontosaurus, Parasaurolophus
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