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Clade
Subclade

Taxon
Taxon
Ornithomimosauria
Nominal Author
Barsbold 1976
2nd Nominal Author
Taxon Status ACTIVE
Comments

Osmólska (1997) was first to define Ornithomimosauria, and did so as a stem-based clade in the context of Holtz’s (1994) phylogeny, with the expectation that troodontids constituted the immediate sister taxon. A problem arises with her use of “bullatosaurs” (ornithomimosaurs + trodontids) in the definition, a clade which has found little support in subsequent analyses.

Independently, and for the two clades Ornithomimosauria and Oviraptorosauria, Sereno (1998) proposed stem-based definitions to incorporate basal taxa and any closely related forms that would be discovered. Ornithomimosauria, for example, was first defined by Sereno (1998) as stem-based to include theropods closer to Ornithomimus than to birds. This definition is not altogether that different from Osmólska's first definition. This definition, however, has not sat well with some (e.g. Padian et al. 1999:78, Kobayashi and Lü 2003, Makovicky et al. 2004), who objected to the inclusion of other groups (e.g. therizinosaurids, alvarezsaurids) when they were positioned as closest relatives to more derived ornithomimosaurs (e.g. Sereno 1999a, b). Indeed, although Sereno’s (1998) definition makes use of an existing name that was originally coined in redundancy with Ornithomimidae, it has come to replace Ornithomimidae over time, with the latter assuming a more restrictive composition within the clade as new basal members are discovered. As late as 1990, however, the family name was used to circumscribe the entire clade (Galton and Smith 1990). Nonetheless, the potential to substantially alter the taxonomic content of Onrithomimosauria, as originally conceived by (Barsbold 1976), is real.

Independently from Sereno, Padian et al. (1999) proposed an opposing solution to the problem presented by Osmólska’s original definition. They recognized a node-based taxon on the basis of currently known taxa—Pelecanimimus and Ornithomimus. This definition has the advantage of overlapping completely with its traditional taxonomic content. But it has disadvantage that any newly discovered, closely related form positioned just outside the named clade will be excluded. The history of Ornithomimosauria, like many clades, is that the younger, more diverse taxa are found first, with ever more basal forms trickling in as the decades pass. Osmólska’s definition, doubtless, was proposed to include newly found basal forms. After all, had Pelecanimimus (Perez-Moreno et al. 1994) been discovered today rather than a decade ago, it would have been excluded from Ornithomimosauria. As it is, there are few characters uniting the recently discovered Shenzhousaurus in a more derived position within the clade (Ji et al. 2003), and no basal resolution in several recent studies (Norell et al. 2001, Xu et al. 2002). No mention is made of the original stem-based definition proposed by Osmólska (1997) in Padian et al. (1999), Kobayashi and Lü (2003), or Makovicky et al. (2004). Surprisingly, in a parallel situation regarding the taxon Oviraptorosauria, Currie and Padian (1997:508) encourage a stem-based definition and the incorporation of extraneous taxa such as Therizinosauroidea.

The both definitional proposals for Ornithomimosauria by Sereno and Padian et al., thus, have drawbacks, and so another option is followed here, one that:

(1) follows Osmólska’s original definition in type and included taxa

(2) maintains current content

(3) allows the incorporation of future discoveries of basal forms

The active definition is stem-based and uses Ornithomimus edmontonicus as an internal specifier, but it excludes (with appropriate external specifiers) well known members of any other clade that has been proposed to have a close relationship with orrnithomimosaurs. Ornithomimiformes Sereno 2005 is erected to accommodate clades such as Alvarezsauridae that may be closer to ornithomimids than to birds.

The main drawback here is that Holtz has redefined Arctometatarsalia from an form-qualified stem-based definition to one that overlaps with the definition proposed here for Ornithomimiformes. Arctometatarsalia has precedence in the date it was coined and in the date of its revised definition. This precedence, while clearly acknowledged, is set aside because such usage differs drastically from the original, controversial taxonomic content of the taxon (see Arctometatarsalia for more background).

It should be noted that Barsbold (1976) appended “Barsbold 1974” to Ornithomimosauria, Oviraptorosauria, and Deinocheirosauria in the publication where they were first used(Barsbold 1976) . The bibliography in Barsbold (1976), however, does not include any 1974 citation. Later, Barsbold (1983) corrected the date of authorship of these three taxa to his 1976 publication.

Potential Synonomy
Arctometatarsalia, Ornithomimosauria

Active Phylogenetic Definition
Active Definition
The most inclusive clade containing Ornithomimus edmontonicus Sternberg 1933 but not Tyrannosaurus rex Osborn 1905, Shuvuuia deserti Chiappe et al. 1998, Therizinosaurus cheloniformis Maleev 1954, Oviraptor philoceratops Osborn 1924, Troodon formosus Leidy 1856, Passer domesticus (Linnaeus 1758).
Shorthand
> Ornithomimus edmontonicus but not Tyrannosaurus rex, Shuvuuia deserti, Therizinosaurus cheloniformis, Oviraptor philoceratops, Troodon for
Definitional Author
Sereno 2005
Definition Status checked
Definition Type STEM
Node-Stem Triplet NO
Other Triplet Taxa
Specifiers
Specifier(s) A
Ornithomimus edmontonicus
Specifier(s) B
Specifier(s) C
Tyrannosaurus rex, Shuvuuia deserti, Therizinosaurus cheloniformis, Oviraptor philoceratops, Troodon formosus, Passer domesticus
Qualifiers
+Taxon
-Taxon
Datum
Taxonomic Content
Publication Year Unknown
Unknown
Unknown
1997

Inactive Taxon Status
Rejection Criteria
Critique
 

Definitional History #1
Earliest Record
All bullatosaurs closer to Orrnithomimus than to Troodon.
Latest Record
Osmolska 1997:499
Range (My)
Range (My)
Orrnithomimus, Troodon
Range (My)

Definitional History #2
Earliest Record
All maniraptoriforms closer to Ornithomimus than to Neornithes.
Latest Record
Sereno 1998:65
Range (My)
Range (My)
Ornithomimus, Neornithes
Range (My)

Definitional History #3
Earliest Record
Pelecanimimus and Ornithomimus and all the descendants of their most recent common ancestor.
Latest Record
Padian et al. 1999:74
Range (My)
Range (My)
Pelecanimimus, Ornithomimus
Range (My)

Definitional History #4
Earliest Record
A node-based taxon derived from the alst common ancestor of the clade defined by Ornithomimus edmontonicus and Pelecanimimus polyodon.
Latest Record
Makovicky et al. 2004:137
Range (My)
Range (My)
Ornithomimus edmontonicus, Pelecanimimus polyodon
Range (My)

Definitional History #5
Earliest Record
Latest Record
Range (My)
Range (My)
Range (My)

Definitional History #6
Earliest Record
Latest Record
Range (My)
Range (My)
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)