Feeding When first described in 1924 by Osborn,
Oviraptor was originally presumed to have been
ovivorous—an organism that has an egg-based diet—based on the association of the holotype with a nest thought to belong to
Protoceratops. In a 1990 conference abstract, David K. Smith presented an osteological reevaluation of
Oviraptor where he rejected the statements made by Barsbold. He found no evidence indicating a forelimb specialized in
aquatic locomotion, and the jaws, rather than preserve a crushing mechanism, preserve shearing surfaces. As the skull is
toothless, lightly built and lacks several strong muscle insertion areas, Smith suggested that
leaves may have been an important part in the diet of
Oviraptor. However, in 1995, Norell and colleagues reported the fragmented remains of a
lizard in the body cavity of the holotype specimen, suggesting that
Oviraptor was partially
carnivorous. of several oviraptorosaur genera In 2008, Stig Olav K. Jansen compared the skull of several oviraptorid species to those of
birds and
turtles to investigate which properties can predict a rhamphotheca. He found the lower jaws of oviraptorids to be very similar to those of
parrots, and the upper jaws to be more similar to those of turtles. Based on these observations, Jansen suggested that oviraptorids were
omnivorous as the sharply developed rhamphotheca together with the prominent forelimbs would have been adapted to catch and tear small
prey. Moreover, the pointed projections of the palate would have contributed in holding prey. Jansen pointed out that a fully
herbivorous diet in oviraptorids seems unlikely as they lacked flat and wide
tomia (cutting edges of the mandibles) to
chew, and were unable to move the lower jaws sideways. However, he considered the lower jaws strong enough to have at least crushed elements like eggs,
nuts or other hard
seeds. Longrich and colleagues in 2010 also rejected a
durophagous (animals that practise shell-crushing) hypothesis, given that such animals typically develop
teeth with broad crushing surfaces. The pointed shape of the dentary bones in the lower jaws suggests that oviraptorids had a sharp-edged rhamphotheca used for shearing food instead. The
symphyseal (bone union) region at the front of the dentary may have given some ability for crushing, but as this was a relatively small area, it was probably not the main function of the jaws. Another argument against them having been eaters of mollusks is the fact that most oviraptorids have been found in
sediments that are interpreted to represent mostly arid or semi-arid environments, such as
Oviraptor in the
Djadokhta Formation. The team also found that oviraptorids and
dicynodonts share cranial features such as short, deep, and toothless mandibles; elongated dentary symphyses; elongated mandibular openings; and a pointed palate. Modern animals with jaws that resemble those of oviraptorids include parrots and
tortoises; the latter group also has tooth-like projections on the palatal region. Longrich and colleagues concluded that due to the similarities between oviraptorids and herbivorous animals, the bulk of their diet would most likely have been formed by plant material. The jaws of oviraptorids may have been specialised for processing food, such as
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.
Reproduction Since the description of the
embryonic
Citipati specimen in 1994, oviraptorids became more understood: instead of having been egg-eating animals, they actually brooded and cared for the
nests. This specimen showed that the holotype of
Oviraptor was likely a
sexually mature individual that perished
incubating the associated nest with
eggs. 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
feathers. Given that the most complete oviraptorid nesting specimen—at the time, the 1995
Citipati nesting specimen—was found in a very avian-like posture, with the forelimbs in a near-folded posture and the pectoral region, belly, and feet in contact with the eggs, Hopp and Orsen indicated that long
pennaceous feathers and a
feather covering were most likely present in life. The "wings" and tail of oviraptorids would have granted protection for the eggs and
hatchlings against climate factors like the
sunlight,
wind, and
rainfalls. However, the arms of this specimen were not extremely folded as in some modern birds, instead, they are more extended resembling the style of large
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. 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
Nanxiong Formation. This new specimen was found preserving mainly the pelvic region with two eggs inside and thereby indicating a
female. The size and position of the eggs suggest that oviraptorids retained two functional
oviducts, but had reduced the number of eggs
ovulated to one per oviduct. David J. Varricchio and colleagues in 2008 found that the relatively large egg clutch-size of oviraptorids and
troodontids is most similar to those of modern birds that practice
polygamous mating and extensive male
parental care, such as
ratite birds, suggesting similar habits. This
reproductive system is most likely to represent the ancestral condition for modern birds, with biparental care (where both parents participate) being a later development. 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
display behaviour, such as
courtship display. The tail of several oviraptorosaurs and oviraptorids ended in
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. es 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. 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. ==Paleoenvironment==