Oviraptor

Source: Wikipedia, the free encyclopedia.
Not to be confused with Overoraptor.

Oviraptor
Temporal range:
Ma
↓
Holotype specimen of Oviraptor
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: †Oviraptoridae
Subfamily: †Oviraptorinae
Genus: †Oviraptor
Osborn, 1924
Type species
†Oviraptor philoceratops
Osborn, 1924
Synonyms
  • Fenestrosaurus philoceratops Osborn, 1924

Oviraptor (

Djadokhta Formation of Mongolia in 1923 during a paleontological expedition led by Roy Chapman Andrews, and in the following year the genus and type species Oviraptor philoceratops were named by Henry Fairfield Osborn. The genus name refers to the initial thought of egg-stealing habits, and the specific name was intended to reinforce this view indicating a preference over ceratopsian eggs. Despite the fact that numerous specimens have been referred to the genus, Oviraptor is only known from a single partial skeleton regarded as the holotype, as well as a nest
of about fifteen eggs and several small fragments from a juvenile.

Oviraptor was a rather small feathered oviraptorid, estimated at 1.6–2 m (5.2–6.6 ft) long with a weight between 33–40 kg (73–88 lb). It had a wide lower jaw with a skull that likely had a crest. Both upper and lower jaws were toothless and developed a horny beak, which was used during feeding along the robust morphology of the lower jaws. The arms were well-developed and elongated ending in three fingers with curved claws. Like other oviraptorids, Oviraptor had long hindlimbs that had four-toed feet, with the first toe reduced. The tail was likely not very elongated, and ended in a pygostyle that supported large feathers.

The initial relationships of Oviraptor were poorly understood at the time and was assigned to the unrelated Ornithomimidae by the original describer, Henry Osborn. However, re-examinations made by Rinchen Barsbold proved that Oviraptor was distinct enough to warrant a separate family, the Oviraptoridae. When first described, Oviraptor was interpreted as an egg-thief, egg-eating dinosaur given the close association of the holotype with a dinosaur nest. However, findings of numerous oviraptorosaurs in nesting poses have demonstrated that this specimen was actually brooding the nest and not stealing nor feeding on the eggs. Moreover, the discovery of remains of a small juvenile or nestling have been reported in association with the holotype specimen, further supporting parental care.

History of discovery

Djadokhta Formation

The first remains of Oviraptor were discovered on reddish

ceratopsian. However, Osborn suggested that the name Oviraptor could reflect an incorrect perception of this dinosaur. Furthermore, Osborn found Oviraptor to be similar to the unrelated—at the time, however, considered related—fast-running ornithomimids based on the toothless jaws, and assigned Oviraptor to the Ornithomimidae.[1] Osborn had previously reported the taxon as "Fenestrosaurus philoceratops",[2] but this was later discredited.[1]

Nest AMNH 6508, which was found in association with the holotype

In 1976, the Mongolian paleontologist Rinchen Barsbold noted some inconsistencies regarding the taxonomic placement of Oviraptor and concluded that this taxon was quite distinct from ornithomimids based on anatomical traits. Under this consideration, he erected the Oviraptoridae to contain Oviraptor and close relatives.[3] After Osborn's initial description of Oviraptor, the egg nest associated with the holotype was accepted to have belonged to Protoceratops,[4][5] and oviraptorids were largely considered to have been egg-eating theropods.[6] Nevertheless, in the 1990s, the discovery of numerous nesting and nestling oviraptorid specimens proved that Osborn was correct in his caution regarding the name of Oviraptor. These findings showed that oviraptorids brooded and protected their nests by crouching on them. This new line of evidence showed that the nest associated with the holotype of Oviraptor belonged to it and the specimen was actually brooding the eggs at the time of death, not preying on them.[7][8][9]

Referred specimens

Mounted MPC-D 100/42; a specimen that became the major reference for Oviraptor but was later disproven due to cranial differences

After the naming of Oviraptoridae in 1976, Barsbold referred six additional specimens to Oviraptor, including two particular specimens under the number MPC-D 100/20 and 100/21.[3] In 1986, Barsbold realized that the latter two did not belong to the genus and instead they represented a new oviraptorid: Conchoraptor.[10] Most of the other specimens are also unlikely to belong to Oviraptor itself, and they have been assigned to other oviraptorids.[11][12] A partial individual also with eggs from the Bayan Mandahu Formation of Mongolia was referred in 1996 by Dong Zhiming and Philip J. Currie, the specimen IVPP V9608.[9] However, in 2010 Nicholas R. Longrich and the two latter paleontologist have expressed their uncertainties regarding this referral as there are several anatomical differences such as the hand phalangeal proportions. They concluded that this specimen was a different and indeterminate species not referrable to this taxon.[13] In 1981, Barsbold referred the specimen MPC-D 100/42 to Oviraptor, a very well-preserved and rather complete individual from the Djadokhta Formation.[14] Since the known elements of Oviraptor were so fragmentary compared to other members, MPC-D 100/42 became the prime reference/depiction of this taxon being prominently labelled as Oviraptor philoceratops in scientific literature.[15][11]

Line drawing of the arms preserved within the holotype

This conception was refuted by

Mark A. Norell and colleagues in 2018 reported a new specimen of Oviraptor: AMNH 33092, which is composed of a tibia and two metatarsals of a nestling or very small juvenile. AMNH 33092 was found in association with the holotype and it was likely part of the nest. Oviraptor is now known from the holotype with associated eggs, and a juvenile/nestling.[19]

Description

Size comparison of the holotype

The holotype specimen has been estimated at 1.6–2 m (5.2–6.6 ft) in length with a weight ranging from 33 to 40 kg (73 to 88 lb).

feathers, and the tail ended in a pygostyle, which is known to support a fan of feathers.[23][24]

Skull

Osborn's line drawing of the holotype skull

The

rhamphotheca (horny beak). The curvature of the dentary tip was down-turned but less pronounced than other oviraptorids, such as Citipati. As a whole, the lower jaw is a short and deep bone that covers 19.5 cm (195 mm).[16]

Postcranial skeleton

Skeletal reconstruction of the holotype, known remains in white

As in most oviraptords, the neural spines of the holotype

dorsal vertebrae when seen in a lateral view and larger than the spines of the cervicals. On the anteriormost dorsal vertebra several pleurocoels (small air-spaced holes) can be found, which are similar to those of Khaan.[25]

The furcula of Oviraptor is very distinct from other oviraptorids in having a midline keel on the anterior surface of the hypocleidium−a downwards directed projection at the center of the furcula. This bone is V-shaped, rounded in cross-section, preserves an elongate spike-like hypocleidium, and the interclavicular angle is about 90°.[26] The scapulocoracoid is fused in the holotype, however, the coracoid is badly damaged. The scapula is slightly bowed and measures 23 cm (230 mm) in length. Oviraptor had a relatively elongated arm composed of the humerus, radius, ulna, and manus.[1][25]

Life restoration

The phalangeal formula of Oviraptor was 2-3-4, as seen in most other theropods and oviraptorids. The hand of Oviraptor had three skinny and bird-like fingers with each finger ended in side to side flattened and recurved

elongatoolithid eggs, with each egg being 14 cm (140 mm) long (some are incomplete). Nevertheless, there is the possibility that taphonomical crushing may have compressed them by up to 2 cm (20 mm).[7][28]

Classification

Oviraptor was originally allied with the

type genus of the Oviraptoridae.[3] During the redescription of the holotype skull in 2002 by Clark and colleagues, they noted that Oviraptor had a relatively elongated maxilla and dentary. These traits are less pronounced in derived oviraptorids and suggests that Oviraptor belongs to the near base of the Oviraptoridae.[16]

The cladogram below follows an analysis by Gregory F. Funston and colleagues in 2020:[29]

Oviraptoridae

Nankangia

unnamed

Oviraptor

unnamed

Yulong

unnamed

Citipatiinae

Heyuanninae

Paleobiology

Feeding

Restored holotype skull of Oviraptor

When first described in 1924 by Osborn, Oviraptor was originally presumed to have been

carnivorous.[32]

lower jaw
of several oviraptorosaur genera

In 2008, Stig Olav K. Jansen compared the skull of several oviraptorid species to those of

seeds.[33]

Longrich and colleagues in 2010 also rejected a

xerophytic vegetation−a vegetation that is adapted for environments with little water—that would have grown in their arid environments, but this is not possible to demonstrate, as little is known about the paleoflora of the Gobi Desert.[13]

In 2018 however, Funston and colleagues supported the crushing jaw hypothesis. They pointed out that the stocky

frugivorous diet that incorporated nuts and seeds.[34]

Reproduction

Citipati nesting specimen
Oviraptor nest AMNH 6508

Since the description of the

sandstorm during incubation. They ruled out the possibility of oviraptorids being egg-thieves as they would have either consumed or instinctively abandoned the nest long before it was buried by a sandstorm or another meteorological phenomenon.[9]

In 1999 Clark and team described in detail the previously reported Citipati nesting specimen and briefly discussed the holotype specimen of Oviraptor and its association with the nest AMNH 6508. They pointed out that the exact position in which the holotype was found over the nest is unclear as they were separated during preparation, and the nest appears to be not entirely complete with about 15 eggs preserved of which two damaged. Moreover, the semicircular arrangement of the nest indicates that the eggs were laid in pairs and in at least three rings, and this nest was originally circular, similar to a mound.[28]

Thomas P. Hopp and Mark J. Orsen in 2004 analyzed the brooding behavior of extinct and extant dinosaur species, including oviraptorids, in order to evaluate the reason for the elongation and development of wing and tail

flightless birds like the ostrich. The extended position of the arm is also similar to the brooding behavior of this bird, which is known to nest in large clutches like oviraptorids. Based on the forelimb position of nesting oviraptorids, Hopp and Orsen proposed brooding as the ancestral reason behind wing and tail feather elongation, as there was a greater need to provide optimal protection for eggs and juveniles.[35]

Life restoration of a nesting Oviraptor. Oviraptorids may have sat on their nests during incubation

In 2005, Tamaki Sato and team reported an unusual oviraptorid specimen from the

pygostyles, a bony structure at the end of the tail that, at least in modern birds, is used to support a feather fan. Furthermore, the tail was notably muscular and had a pronounced flexibility, which may have aided in courtship movements.[24]

egg clutches from the Nanxiong Formation

In 2018, Tzu-Ruei Yang and colleagues identified cuticle layers on several egg-shells of maniraptoran dinosaurs including those of oviraptorids. These particular layers are composed of proteins, polysaccharides and pigments, but mainly of lipids and hydroxyapatite. In modern birds they serve to protect the eggs from dehydration and invasion of microorganisms. As most oviraptorid specimens have been found in formations of caliche-based sedimentation, Yang and colleagues suggested that the cuticle-coated eggs would have been a reproductive strategy adapted for enhancing their hatching success in such arid climates and environments.[38]

In 2019 Yang and colleagues re-evaluated the hypothesis of

thermoregulatory contact incubation using complete oviraptorid nests from the Nanxiong Formation, and provided a detailed reconstruction of the architecture of the oviraptorid clutch. They noted that adult oviraptorid specimens in association with nest were not necessarily incubating the eggs as they could represent a female in the process of laying eggs, and the multi-ring clutch prevented sufficient heat transfer from the parent to the inner rings of eggs. An average oviraptorid nest was built as a gently-inclined mound with a highly organized architecture: the eggs were likely pigmented and arranged in pairs with each pair arranged in three to four elliptical rings. As the parent was likely operating from the nest center, this region was devoid of eggs. Yang and colleagues concluded the oviraptorid nesting style was so unique that they lack modern analogs, therefore, using oviraptorid reproduction may not be the best example to inform about the evolution of bird reproductive strategies. However, the team was unable to determinate if the juvenile Oviraptor AMNH 33092 had hatched from the nest associated with the holotype.[39]

Paleoenvironment

Restoration of a resting Oviraptor at the Djadokhta Formation

Oviraptor is known from the Bayn Dzak locality of the

fluvial sedimentation.[43] Furthermore, it is thought that later in the Campanian age and into the Maastrichtian, the climate would shift to the more humid fluvial environment seen in the Nemegt Formation.[42]

The Djadokhta Formation is separated into a lower Bayn Dzak Member and an upper Turgrugyin Member. The known remains of Oviraptor have been produced by the Bayn Dzak member, which has also yielded the dinosaurs

Shuuvuia, Tsaagan,[43] and Minotaurasaurus.[45]

Taphonomy

The pose of the holotype of Oviraptor along with the association of eggs, suggest that it was trapped over the nest during a

sandstorm, and burial was relatively rapid given that the body had no opportunity to become fully disarticulated or scavenged by predators.[1][9] The paleontologist Kenneth Carpenter also agreed in that sandstorms may have been the most likely event that the eggs found in the deposits were buried.[46] Among elements, the skull have become particularly flattened and distorted during the fossilization process.[16]

See also

References

  1. ^
    OCLC 40272928
    .
  2. ^ Osborn, H. F. (1924). "The discovery of an unknown continent". Natural History. 24 (2): 133−149.
  3. ^
    theropods
    Oviraptoridae n. fam. in Mongolia]. Doklady Akademii Nauk SSSR. 226 (3): 685−688.
  4. ISBN 0-8137-2238-1
    .
  5. doi:10.1111/j.1502-3931.1992.tb01379.x
    .
  6. doi:10.1139/e93-196
    .
  7. ^
    S2CID 22333224
    .
  8. ^
    S2CID 4245228
    .
  9. ^
    doi:10.1139/e96-046
    .
  10. ^ a b Barsbold, R. (1986). "Хищные динозавры овирапторы" [Carnivorous dinosaurs oviraptors]. In Vorobyeva, E. I. (ed.). Herpetological research in the Mongolian People's Republic (in Russian). Institute of Evolutionary Morphology and Ecology of Animals: Doklady Akademii Nauk SSSR. pp. 210–223.
  11. ^ a b Maryańska, T.; Osmólska, H.; Wolsan, M. (2002). "Avialan status for Oviraptorosauria" (PDF). Acta Palaeontologica Polonica. 47 (1): 97−116.
  12. S2CID 40622976
    .
  13. ^
    doi:10.1111/j.1475-4983.2010.00968.x
    .
  14. S2CID 195060070. Translated paper
  15. ISBN 9780520067271
    .
  16. ^
    S2CID 52247789
    .
  17. ^ Barsbold, 1997. Oviraptorosauria. In Currie and Padian (eds.). Encyclopedia of Dinosaurs. 505-509.
  18. ISBN 0520242092
    .
  19. ^
    S2CID 53057001
    .
  20. PMID 23991160
    .
  21. ISBN 9780691167664
    .
  22. S2CID 221404013
    .
  23. PMID 22347465
    .
  24. ^
    doi:10.4202/app.2012.0093
    .
  25. ^
    S2CID 86067306
    .
  26. PMID 19206153
    .
  27. S2CID 206871470
    .
  28. ^
    hdl:2246/3102
    .
  29. PMID 33204472
    .
  30. ^ Barsbold, R. (1977). "Kinetism and peculiarity of the jaw apparatus of oviraptors (Theropoda, Saurischia)". Soviet-Mongolian Paleontological Expedition, Trudy. 4: 37−47. Translated paper
  31. doi:10.1080/02724634.1990.10011841
    .
  32. ^ Norell, M. A.; Gaffney, E. S.; Dingus, L. (1995). Discovering Dinosaurs In the American Museum of Natural History. Knopf Inc. p. 225.
  33. hdl:10852/11785
    .
  34. doi:10.1016/j.palaeo.2017.10.023
    .
  35. ^ Hopp, T. P.; Orsen, M. J. (2004). "Dinosaur Brooding Behavior and the Origin of Flight Feathers" (PDF). In Currie, P. J.; Koppelhus, E. B.; Shugar, M. A.; Wright, J. L. (eds.). Feathered dragons: studies on the transition from dinosaurs to birds. Bloomington: Indiana University Press. pp. 234−250.
  36. S2CID 19470371
    .
  37. PMID 19095938
    .
  38. PMID 30002976
    .
  39. doi:10.4202/app.00497.2018
    .
  40. ^
    S2CID 55836458
    .
  41. ISBN 978-0-12-226810-6
    .
  42. ^
    PMID 28724887
    .
  43. ^
    S2CID 129735494.[permanent dead link
    ]
  44. S2CID 4471941
    .
  45. ^ Alicea, J.; Loewen, M. (2013). "New Minotaurasaurus material from the Djodokta Formation establishes new taxonomic and stratigraphic criteria for the taxon". Journal of Vertebrate Paleontology. Program and Abstracts: 76. Archived from the original on 2020-11-01. Retrieved 2020-11-19.
  46. ISBN 9780253334978
    .

External links

  • Media related to Oviraptor at Wikimedia Commons
  • Data related to Oviraptor at Wikispecies
  • Oviraptor nest AMNH 6508 photographs at AMNH
  • Oviraptor holotype skull photograph at AMNH
Retrieved from "https://en.wikipedia.org/w/index.php?title=Oviraptor&oldid=1219071977"