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Clade
Subclade

Taxon
Taxon
Saurischia
Nominal Author
Seeley 1888
2nd Nominal Author
Taxon Status ACTIVE
Comments

The active definition is a first-order revision of Sereno (1998) and of the first phylogenetic definition for Saurischia, which was proposed by Gauthier (1986). Gauthier used supraspecific taxa and common names (i.e. Ornithischia and “birds”) as specifiers. Later, formal taxa replaced one specifier (Padian 1997; Triceratops) or both (Sereno 1998; Triceratops, Neornithes). Finally, Langer (2004) used Allosaurus and Stegosaurus as specifiers but did not provide any explanation for that choice. The active definition uses deeply nested species.

Saurischian monophyly is not supported by that many synapomorphies; it is conceivable that ornithischians and sauropodomorphs may eventually prove to be more closely related. If that turns out to be the case, then Saurischia would identify the same clade as the taxon Theropoda. To avoid questions of synonomy and to ensure that the name Saurischia is restricted fo a clade composed of theropods and sauropodomorphs but not all dinosaurs, a positive taxon qualifier is added (the derived sauropodomorph Saltasaurus loricatus) that would negate use of the Saurischia if this species were not included.

Another phylogenetic arrangement—with ornithischians most closely related to birds (e.g. Galton 1970) than to nonavian theropods or sauropodomorphs—has never been supported by cladistic analysis and is not regarded here as a realistic possibility .

Potential Synonomy

Active Phylogenetic Definition
Active Definition
The most inclusive clade containing Passer domesticus (Linnaeus 1758) but not Triceratops horridus Marsh 1889 and including Saltasaurus loricatus Bonaparte and Powell 1980.
Shorthand
> Passer domesticus but not Triceratops horridus + Saltasaurus loricatus.
Definitional Author
Sereno 2005
Definition Status checked
Definition Type STEM
Node-Stem Triplet STEM
Other Triplet Taxa
Dinosauria, Ornithischia
Specifiers
Specifier(s) A
Passer domesticus
Specifier(s) B
Specifier(s) C
Triceratops horridus
Qualifiers
+Taxon
Saltasaurus loricatus
-Taxon
Datum
Taxonomic Content
Publication Year Unknown
Unknown
Unknown
1986

Inactive Taxon Status
Rejection Criteria
Critique
 

Definitional History #1
Earliest Record
Birds and all dinosaurs that are closer to birds than they are to Ornithischia.
Latest Record
Gauthier 1986:15
Range (My)
Range (My)
birds, Ornithischia
Range (My)

Definitional History #2
Earliest Record
All dinosaurs closer to birds than to Ornithischia.
Latest Record
Padian and May 1993:379
Range (My)
Range (My)
birds, Ornithischia
Range (My)

Definitional History #3
Earliest Record
All dinosaurs closer to birds than to Triceratops.
Latest Record
Padian 1997:647
Range (My)
Range (My)
birds, Triceratops
Range (My)

Definitional History #4
Earliest Record
All dinosaurs closer to Neornithes than to Triceratops.
Latest Record
Sereno 1998:63
Range (My)
Range (My)
Range (My)

Definitional History #5
Earliest Record
All dinosaurs more closely related to Tyrannosaurus than to Triceratops.
Latest Record
Holtz and Osmlska 2004:21
Range (My)
Range (My)
Tyrannosaurus, Triceratops
Range (My)

Definitional History #6
Earliest Record
All dinosaurs that share a more recent common ancestor with Allosaurus than with Stegosaurus.
Latest Record
Langer 2004:25
Range (My)
Range (My)
Allosaurus, Stegosaurus
Range (My)

Definitional History #7
Earliest Record
Latest Record
Range (My)
Range (My)
Range (My)

Definitional History #8
Earliest Record
Latest Record
Range (My)
Range (My)
Range (My)

Definitional History #9
Earliest Record
Latest Record
Range (My)
Range (My)
Range (My)

Definitional History #10
Earliest Record
Latest Record
Range (My)
Range (My)
Range (My)