Oviraptoridae is a group of bird-like, herbivorous and omnivorous maniraptoran dinosaurs. Oviraptorids are characterized by their toothless, parrot-like beaks and, in some cases, elaborate crests. They were generally small, measuring between one and two metres long in most cases, though some possible oviraptorids were enormous. Oviraptorids are currently known only from the Late Cretaceous of Asia, with the most well-known species and complete specimens found only in the Gobi Desert of Mongolia and northwestern China. Description The most characteristic feature of this group is the skull structure. Oviraptorids had short snouts and very deep mandibles. Some taxa (such as Citipati, Corythoraptor, Rinchenia) had a midline crest on top of the skull, resembling that of a cassowary. Other distinguishing characteristics 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 roof of the mouth. Classification The classification of the oviraptorids has been controversial. Most studies divide oviraptorosaurs into two primary sub-groups, the Caenagnathidae and the Oviraptoridae. However, some phylogenetic studies have suggested that many traditional members of the Caenagnathidae may be more closely related to the crested oviraptorids. Because of this, and the fact that at least one study found that Caenagnathus itself may not have been part of the 'caenagnathid' group, Tom Holtz (2010) placed that group close to the Oviraptoridae and termed it the Elmisauridae, though this idea has not gained consensus among other researchers. The Oviraptoridae itself is traditionally divided into two "subfamilies": the small, short-armed, and mainly crestless subfamily Heyuanniinae and the larger, crested, long-armed Oviraptorinae (Oviraptor + Citipati). Some phylogenetic studies have shown that Oviraptor is the most primitive known oviraptorid, thus making Citipati a closer relative of the "ingeniines" and this traditional division into crestless and crested forms artificial. Other possible oviraptorids include Nomingia gobiensis, Gigantoraptor erlianensis, Jiangxisaurus ganzhouensis and Shixinggia oblita. All four have been suggested to be oviraptorids, caenagnathids, or more primitive than either group. The below cladogram was found in the description of the genus Anzu. In 2020, during their description of Oksoko, Funston et al. recovered a slightly different cladogram. Because Oviraptor did not clade with Citipati and the other "oviraptorines", they named the latter's clade Citipatiinae, although they