Oviraptoridae

Oviraptoridae is a group of Maniraptoran dinosaurs which lived in the Late Cretaceous period. They are currently known from Mongolia and China, though there is an unpublished report from Montana. These animals were small, measuring up to 2 m long in most cases.

Oviraptoridae includes - Oviraptor philoceratops, from the Late Cretaceous of Mongolia. Found in 1924, it has a longer snout and seemingly extensive crest on its head. Most illustrations of it are actually based on Citipati. "Rinchenia" mongoliensis was first called Oviraptor mongoliensis and has yet to be officially renamed. It has a very high crest on the center of its head, and is from the Late Cretaceous of Mongolia as well. Citipati osmolskae was recently named, but a skeleton was found in the 1980s belonging to it that was thought to be Oviraptor until recently. It has an anteriorly placed crest, and lived at the same time and place as Oviraptor. Conchoraptor gracilis is a small crestless form with a slender second toe. Many specimens have been referred to it, but there have been no detailed studies showing exactly which ones are correctly referred. Khaan mckennai is another new taxon that closely resembles Conchoraptor, but has a reduced third finger. It lived alongside Citipati. Ingenia yanshini has also had a lot of material referred to it that probably doesn't belong. It was contemporaneous with Conchoraptor, and work needs to be done separating their remains from each other. Ingenia's hand is distinguished by a very large first finger and reduced second and third fingers. Heyuannia huangi is the first named oviraptorid from China and resembles Ingenia closely, but is distinguished by having more hip vertebrae and the first finger fused with the wrist.

Other possible oviraptorids include Nomingia gobienisis and the early Microvenator celer. Both have been suggested to be close to oviraptorids, caenagnathids, or more primitive than either group.

The most characteristic feature of this group is the skull structure. Oviraptorids had short snouts and very deep mandibles. Some taxa (Oviraptor, Citipati, "Rinchenia") had a midline crest on top of the skull, resembling that of a cassowary. Other distinguishing characters include a bony spike intruding on the mandibular fenestra, nostrils placed very high and far back on the snout, an extremely thin bony bar beneath the eye, and highly pneumatized skull bones. Like their relatives the caenagnathids, the jaws were edentulous (with no teeth), having instead two small bony projections on the top jaw.

The eating habits of these animals are not fully known, but some ate small vertebrates. Evidence for this comes from a lizard skeleton preserved in the body cavity of Oviraptor and two baby troodontid skulls found in a Citipati nest. There are also arguments for the inclusion of plant material or mollusks in their diet. Originally they were thought to be egg raiders, based on a Mongolian find showing Oviraptor on top of a nest. Recent studies have shown that in fact the animal was on top of its own nest. Another finding shows a Citipati on top of a nest, while brooding the eggs with its arms. There are a few other oviraptorid specimens preserved on nests as well, and a Citipati embryo was discovered inside the same kind of egg preserved in these nests.

Oviraptorids were probably feathered, since some close relatives were found with feathers preserved (Caudipteryx and possibly Protarchaeopteryx). Another finding pointing to this is the discovery in Nomingia gobiensis of a pygostyle, a bone that results from the fusion of the last tail vertebrae and is responsible in birds to hold a fan of feathers in the tail. Finally, the arm position of the brooding Citipati would have been far more effective if feathers were present to cover the eggs.de:Oviraptoridae