Ornithomimosauria

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Ornithomimosaurs
Temporal range:
Ma[1]
Collection of seven ornithomimosaurs, clockwise from top left:
Gallimimus mongoliensis
"
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Maniraptoriformes
Clade: †Ornithomimosauria
Barsbold, 1976
Subgroups[7]
Synonyms
  • Deinocheirosauria Barsbold, 1976
  • Arctometatarsalia Holtz, 1994

Ornithomimosauria ("

Period of Laurasia (now Asia, Europe and North America), as well as Africa and possibly Australia.[8] The group first appeared in the Early Cretaceous and persisted until the Late Cretaceous. Primitive members of the group include Nqwebasaurus, Pelecanimimus, Shenzhousaurus, Hexing and Deinocheirus, the arms of which reached 2.4 m (8 feet) in length. More advanced species, members of the family Ornithomimidae, include Gallimimus, Struthiomimus, and Ornithomimus. Some paleontologists, like Paul Sereno, consider the enigmatic alvarezsaurids
to be close relatives of the ornithomimosaurs and place them together in the superfamily Ornithomimoidea (see classification below).

Description

Life restorations of Garudimimus (top) and Gallimimus (bottom)

The skulls of ornithomimosaurs were small, with large eyes, above relatively long and slender necks. The most basal members of the taxon (such as

coelurosaurs
, the ornithomimosaurian hide was feathered rather than scaly.

Feathers

Unambiguous evidence of feathers is known from

pennaceous feathers seen in Pennaraptora.[12] Otherwise, a very ostrich-like plumage and feather range is known in one specimen of Ornithomimus.[13]

Classification

Named by

cladistic
definitions began to appear for the groups in the 1990s.

In the early 1990s, prominent paleontologists such as

arctometatarsalian pes and all of its descendants." This group included the Troodontidae, Tyrannosauroidea, and Ornithomimosauria. Holtz (1996, 2000) later refined this definition to the branch-based "Ornithomimus
and all theropods sharing a more recent common ancestor with Ornithomimus than with birds." Subsequently, the idea that all arctometatarsalian dinosaurs formed a natural group was abandoned by most paleontologists, including Holtz, as studies began to demonstrate that tyrannosaurids and troodontids were more closely related to other groups of coelurosaurs than they were to ornithomimosaurs. Since the strict definition of Arctometatarsalia was based on Ornithomimus, it became redundant with the name Ornithomimosauria under broad definitions of that clade, and the name Arctometatarsalia was mostly abandoned.

The

Passer domesticus. Because he had redefined Ornithomimosauria in a much narrower sense, a new term was made necessary within his preferred terminology to denote the clade containing the sistergroups Ornithomimosauria and Alvarezsauridae — previously the latter had been contained within the former. However, this concept only appeared on Sereno's Web site and has not yet been officially published as a valid name.[14] "Ornithomimiformes" was identical in content to Holtz's Arctometatarsalia, as it has a very similar definition. While "Ornithomimiformes" is the newer group, Sereno rejected the idea that Arctometatarsalia should take precedence, because the meaning of the former name has been changed very radically by Holtz.[14]

Phylogeny

Beishanlong grandis

Ornithomimosauria has variously been used for the branch-based group of all dinosaurs closer to Ornithomimus than to birds, and in more restrictive senses. The more exclusive sense began to grow in popularity when the possibility arose that alvarezsaurids might fall under Ornithomimosauria if an inclusive definition were adopted. Another clade, Ornithomimiformes, was defined by Sereno (2005) as (Ornithomimus velox > Passer domesticus) and replaces the more inclusive use of Ornithomimosauria when alvarezsaurids or some other group are found to be closer relatives of ornithomimosaurs than maniraptorans, with Ornithomimosauria redefined to include dinosaurs closer to Ornithomimus than to alvarezsaurids. Gregory S. Paul has proposed that Ornithomimosauria might be a group of primitive, flightless birds, more advanced than Deinonychosauria and Oviraptorosauria.[15]

The cladogram below follows an analysis by Yuong-Nam Lee, Rinchen Barsbold, Philip J. Currie, Yoshitsugu Kobayashi, Hang-Jae Lee, Pascal Godefroit, François Escuillié & Tsogtbaatar Chinzorig. The analysis was published in 2014, and includes many ornithomimosaurian taxa.[7]

Coelurosauria

The cladogram below follows the phylogenetic analysis by Scott Hartman and colleagues in 2019, which has included a vast majority of species and uncertain specimens, resulting in a novel phylogenetic arrangement.[16]

Ornithomimosauria

Below is a cladogram by Serrano-Brañas et al., 2020, showing an analysis more in line with previous assumptions about ornithomimosaur classification.[17]

Ornithomimosauria

Palaeobiology

Ornithomimosaurs probably acquired most of their calories from plants. Many ornithomimosaurs, including primitive species, have been found with numerous gastroliths in their stomachs, characteristic of herbivores. Henry Fairfield Osborn suggested that the long, sloth-like "arms" of ornithomimosaurs may have been used to pull down branches on which to feed, an idea supported by further study of their strange, hook-like hands.[18] The sheer abundance of ornithomimids — they are the most common small dinosaurs in North America — is consistent with the idea that they were plant eaters, as herbivores usually outnumber carnivores in an ecosystem. However, they may have been omnivores that ate both plants and small animal prey.

Comparisons between the

cathemeral, active throughout the day at short intervals.[19]

Social behavior

Block containing eight specimens of Sinornithomimus

Ornithomimosaurs are fairly well known for their gregarious life-styles. Some of the first findings of ornithomimosaur

social behaviour of a single species given the identification of at least two different taxa. Under this consideration, it is possible that a small pack of more than 10 individuals of different ornithomimosaurian herds was travelling together in optimal areas to find food resources, nesting sites or something else.[22][23]

See also

References

  1. ^ a b Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
  2. ^ Brownstein CD. (2016) Redescription of Arundel formation Ornithomimosaur material and a reinterpretation of Nedcolbertia justinhofmanni as an "Ostrich Dinosaur": Biogeographic implications. PeerJ Preprints 4:e2308v1 https://doi.org/10.7287/peerj.preprints.2308v1
  3. doi:10.1016/j.jafrearsci.2012.05.005
    .
  4. doi:10.1093/zoolinnean/zlab013
    .
  5. S2CID 134718338
    .
  6. Bibcode:2012bdec.book.....G
    .
  7. ^
    S2CID 2986017
    .
  8. doi:10.1016/j.jafrearsci.2012.05.005
    .
  9. ^ Last of the Dinosaurs: The Cretaceous Period
  10. doi:10.1016/j.cretres.2015.10.004
    .
  11. S2CID 2986017
    .
  12. S2CID 4464659
    .
  13. doi:10.1016/j.cretres.2015.10.004
    .
  14. ^ a b Sereno, P. C. (2005). Stem Archosauria—TaxonSearch Archived 2009-01-15 at the Wayback Machine [version 1.0, 2005 November 7]
  15. ^ Paul, G.S. (2002). Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Baltimore: Johns Hopkins University Press.
  16. PMID 31333906
    .
  17. S2CID 218968100
    .
  18. ^ Nicholls and Russell (1985).
  19. ^ Schmitz and Motani (2011)
  20. hdl:2246/355
    .
  21. ^ Kobayashi, Y.; Lü, J.-C. (2003). "A new ornithomimid dinosaur with gregarious habits from the Late Cretaceous of China" (PDF). Acta Palaeontologica Polonica. 48 (2): 235−259.
  22. ^ Chinzorig, T.; Kobayashi, Y.; Saneyoshi, M.; Tsogtbaatar, K.; Batamkhatan, Z.; Ryuji, T. (2017). "Multitaxic bonebed of two new ornithomimids (Theropoda, Ornithomimosauria) from the Upper Cretaceous Bayanshiree Formnation of southeastern Gobi desert, Mongolia". Journal of Vertebrate Paleontology. Program and Abstracts: 97.
  23. hdl:2115/74432
    .

Further reading

External links

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