Citipati

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Citipati
Temporal range:
Ma
Nesting Citipati specimen nicknamed "Big Mama", at the American Museum of Natural History
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Oviraptoridae
Subfamily: Oviraptorinae
Genus: Citipati
Clark et al., 2001
Type species
Citipati osmolskae
Clark et al., 2001

Citipati (

brooding positions atop nests of eggs, though most of them were initially referred to the related Oviraptor. These nesting specimens have helped to solidify the link between non-avian dinosaurs and birds
.

Citipati was among the largest oviraptorids; it is estimated to have been around 2.5–2.9 m (8.2–9.5 ft) in length and to have weighed 75–83 kg (165–183 lb). Its skull was highly

rectrices
.

The taxon is classified as an oviraptorid, a group of very bird-like feathered dinosaurs that had robust, parrot-like jaws. It is among the oviraptorid species that preserve nesting specimens. Citipati laid

nest parasitism
.

History of discovery

Citipati embryo IGM 100/971

In 1993, a small fossilized oviraptorid embryo, labelled as specimen IGM 100/971, was discovered in a nest at the Ukhaa Tolgod locality of the highly fossiliferous

Mark A. Norell and colleagues in 1993, who considered this oviraptorid embryo to be closely related to the early named Oviraptor, and also as an evidence supporting that oviraptorids were brooding animals.[1] The two perinates would be later identified as individuals belonging to the troodontid Byronosaurus.[2]

Citipati specimen IGM 100/979, popularly known as "Big Mama"

During the same year 1993, expeditions of the paleontological project of the Mongolian Academy of Sciences-American Museum of Natural History discovered a large adult oviraptorid specimen also from the Ukhaa Tolgod locality of the Djadokhta Formation, in a sublocality known as Ankylosaur Flats. This new specimen was labelled under the specimen number IGM 100/979 and includes a partial skeleton comprising some ribs and partial limbs but lacking the skull, neck and tail. It was found in a nesting pose, sitting atop a nest of

elongatoolithid eggs with folded forelimbs and crouched hindlimbs. Similar to the embryonic specimen, IGM 100/979 was considered to be an indeterminate oviraptorid closely related to Oviraptor.[3] The specimen shortly became famous and was nicknamed as "Big Mama" by The New York Times press.[4] A larger and more complete specimen, catalogued as IGM 100/978, was found in 1994 also from the Ankylosaur Flats sublocality by the American Museum–Mongolian Academy of Sciences field expeditions. The specimen was unearthed as a single individual not associated with eggs, and it is represented by a nearly complete skeleton including the skull and much of the postcranial elements. However, it was initially identified as a specimen of Oviraptor.[5]

Citipati specimen IGM 100/1004, also known as "Big Auntie"

In 1995, the Mongolian Academy of Sciences-American Museum of Natural History expedition discovered a second nesting oviraptorid specimen from the Ukhaa Tolgod locality, in a region called Camel's Humps, at the Death Row sublocality. This new specimen was labelled as IGM 100/1004 and nicknamed "Big Auntie".

sacral vertebrae.[7]

In 2001, the

paleontologists James M. Clark, Mark A. Norell and Rinchen Barsbold named the new genus and type species Citipati osmolskae based on the now regarded holotype IGM 100/978, and referred specimens IGM 100/971 (embryo) with 100/979 ("Big Mama"). The generic name, Citipati, is formed from the Sanskrit words citi (meaning funeral pyre) and pati (meaning lord) in reference to the lord of cemeteries in the Tibetan Buddhism folklore, Citipati, which is often depicted as a humanoid skeleton. The specific name, osmolskae, is in honor to the noted Polish paleontologist Halszka Osmólska, whose work dealt extensively with Mongolian theropods.[8]

Description of specimens

Caudal vertebra from the holotype

Though the first specimen of Citipati (IGM 100/971) was briefly reported and discussed, Norell and colleagues in 2001 provided an extensive description of this specimen. As the description was published prior to the formal naming of Citipati, Norell and team tentatively referred this small embryo to a "new large species from Ukhaa Tolgod"—in fact, later known as Citipati osmolskae—based on the shared tall premaxilla morphology among specimens.[9] The more famous IGM 100/979 was extensively described by Clark and team in 1999, also prior to the naming of Citipati. They considered this specimen to be most similar and closely related to Oviraptor than to the other oviraptorids known at that time.[10] Despite being discovered in 1995, the specimen IGM 100/1004 remained partially figured and largely undescribed for years until its formal referral to the taxon Citipati osmolskae in 2018 by Norell and team.[7]

The largest and most complete specimen of Citipati is represented by the holotype IGM 100/978, however, it was preliminarily described and figured in 2001 during the naming of the taxon and during that time, the specimen had not been completely prepared.[8] The skull anatomy of the specimen was later described by Clark and colleagues in 2002,[11] the furcula morphology in 2009 by Sterling J. Nesbitt with team,[12] and the caudal vertebrae by W. Scott Persons and colleagues in 2014 who noted the presence of a pygostyle.[13] Subsequent descriptions have been published in 2018 by Norell and team describing and illustrating some cervical vertebrae and uncinate processes,[7] and Amy M. Balanoff and colleagues describing the endocranium anatomy.[14] In 2003 Amy Davidson described the process in which the holotype was prepared,[15] later supplemental by Christina Bisulca and team in 2009 describing conservation treatments of broken bones.[16]

Zamyn Khondt oviraptorid

Mounted IGM 100/42; this specimen has been largely used as a reference for Oviraptor and could represent a second species of Citipati

The Zamyn Khondt oviraptorid is a well-known oviraptorid represented by a single and rather complete specimen (IGM 100/42) collected from the Zamyn Khondt (also spelled as Dzamin Khond) locality of the

Djadokhta Formation. Since the type skull and body remains of Oviraptor are crushed and partially preserved, the Zamyn Khondt oviraptorid had become the quintessential depiction of the former, even appearing in scientific literature with the label Oviraptor philoceratops.[17]

Clark with team have pointed out that this distinctive-looking, tall-crested oviraptorid has more features of the skull in common with Citipati than it does with Oviraptor. Though being different in the crest shape of the skull, the Zamyn Khondt oviraptorid is similar to Citipati in the shape of the narial region and premaxilla morphology. They considered this oviraptorid to belong to the genus, however, they could neither confirm nor disregard that this specimen represents a second species of Citipati.

sister taxon of Citipati.[20]

Description

Size comparison of three specimens of Citipati (holotype, Big Auntie and Big Mama)

Citipati was a large-bodied oviraptorid, with the largest individuals being

feathers, and plumage. Other oviraptorids and oviraptorosaurs are also known to have been feathered.[13][7]

Skull

Line drawing of the holotype skull
Life restoration

Its skull was unusually short and highly

nasal bones of the skull, with a nearly vertical front margin grading into the beak. In contrast, the crest of IGM 100/42 was taller with a prominent notch in the front margin, creating a squared appearance.[11]

Classification

Citipati is often referred to the subfamily

Oviraptorinae along with Oviraptor. However, in 2020, Gregory F. Funston and colleagues found Oviraptor to be more basal, so they named a new subfamily Citipatiinae. The cladogram below follows their analysis:[20]

Oviraptoridae
unnamed

Nankangia

unnamed

Oviraptor

unnamed

Yulong

unnamed
Citipatiinae

Wulatelong

unnamed
unnamed

Rinchenia

Tongtianlong

unnamed

Ganzhousaurus

unnamed
unnamed

Citipati

Zamyn Khondt oviraptorid

unnamed

Huanansaurus

Corythoraptor

Heyuanninae

Shixinggia

unnamed

Khaan

unnamed

Conchoraptor

unnamed

Machairasaurus

unnamed
unnamed

Nemegtomaia

unnamed

Heyuannia huangi

Heyuannia yanshini

unnamed
unnamed

Banji

unnamed

Jiangxisaurus

Oksoko

Paleobiology

Feeding mechanics

Reconstructed jaw musculature of Citipati
Optimal (left) and maximum (right) jaw gapes of Citipati

A 2022 study of the bite force of Citipati and comparisons with other oviraptorosaurs such as Incisivosaurus, Khaan, and Conchoraptor suggests that Citipati had a very strong bite force, scored between 349.3 N and 499.0 N. The moderate jaw gape seen in oviraptorosaurs is indicative of herbivory in the majority of the group, but it is clear they were likely feeding on much tougher vegetation than other herbivorous theropods in their environment, such as ornithomimosaurs and therizinosaurs were able to. The examinations suggest oviraptorosaurs may have been powerful-biting generalists or specialists that partook of niche partitioning both in body size and jaw function. Of the oviraptorids examined in this study, Citipati had one of the most powerful bites, but its biting mechanics were unique among the oviraptorosaurs investigated.[24]

Reproduction

Labelled Citipati embryo IGM 100/971
Life restoration of IGM 100/971

The embryo-bearing egg was otherwise identical to other oviraptorid eggs in shell structure and was found in an isolated nest, again arranged in a circular pattern. Two skulls belonging to very young or embryonic

nest parasitism.[1][2]

Although fossilized dinosaur eggs are rare, Citipati eggs and oviraptorid eggs in general, are relatively well known. Along with the two known nesting specimens, dozens of isolated oviraptorid nests have been uncovered in the

elongatoolithid, which are shaped like elongated ovals and resemble the eggs of ratites in texture and shell structure. In the nest, Citipati eggs are typically arranged in concentric circles of up to three layers, and a complete clutch may have consisted of as many of 22 eggs.[25] The eggs of Citipati are the largest known definitive oviraptorid eggs, at 18 cm. In contrast, eggs associated with Oviraptor are only up to 14 cm long.[10]

The two nesting specimens of Citipati are situated on top of egg clutches, with their limbs spread symmetrically on each side of the nest, front limbs covering the nest perimeter. This brooding posture is found today only in birds and supports a behavioral link between birds and theropod dinosaurs.

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.[26]

In 2014, W. Scott Persons and colleagues suggested that oviraptorosaurs were secondarily flightless and several of the traits in their tails may indicate a propensity for

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.[13]

Paleopathology

Clark and colleagues in 1999 during the description of "Big Mama" noted that the right ulna was badly broken but healed, leaving a prominent callus and possible elongated groove over the injury.[10] As the ulna features positive signs of healing, in 2019 Leas Hearn and team suggested that this individual managed to survive an injury that would have interfered with foraging for several weeks in order to lay and incubate its nest.[27]

In 2002 Clark with team reported a small notch preserved on the right jugal, just beneath the orbit, of the holotype skull of Citipati. This anomaly was likely produced by external damage, leaving a small injury.[11]

Paleoenvironment

Citipati is vastly known from the Ukhaa Tolgod locality of the

Kol and Shuvuuia;[30][31] ankylosaurid Minotaurasaurus;[32] birds Apsaravis and Gobipteryx;[33][34] dromaeosaurid Tsaagan;[35] fellow oviraptorid Khaan;[36] troodontids Almas and Byronosaurus;[37][38] and an undescribed protoceratopsid closely related to Protoceratops.[39]

See also

References

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  5. ^ a b Webster, D. (1996). "Dinosaurs of the Gobi: Unearthing a Fossil Trove". National Geographic. Vol. 190, no. 1. pp. 70–89.
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  22. ^ Paul, Gregory S. (2010). The Princeton Field Guide to Dinosaurs. New Jersey: Princeton University Press. p. 153.
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  24. ^ Varricchio, D.J. (2000). "Reproduction and Parenting," in Paul, G.S. (ed.). The Scientific American Book of Dinosaurs. New York: St. Martin's Press, pp. 279–293.
  25. ^ 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.
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  31. ^ 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 1 November 2020. Retrieved 27 August 2022.
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External links