Oviraptorosauria
 |-Incisivosaurus gauthieri
    |
    |-Caudipteryx zoui
    |-Caudipteryx dongi
    |-Caudipteryx sp
    |-?Avimimus portentosus
    |-?Kakuru kujani
    |-?Protarchaeopteryx robusta
    |-Microvenator celer
       |
       |-?Nomingia gobiensis
          |
          |-Caenagnathidae
          |  |-Caenagnathus martinsonii
          |     |
          |     |-Caenagnathinae (aka Elmisaurinae)
          |        |-Chirostenotes pergracilis
          |        |-?Chirostenotes sternbergi
          |        |-Chirostenotes sp
          |        |-Elmisaurus rarus
          |        |-Elmisaurus elegans
          |
          |-Oviraptidae
          |   |-Ingenia yanshini
          |   |-Khaan mckennai
          |   |-Conchoraptor gracilis
          |   |-Conchoraptor sp
          |   |-Heyuannia huangi
          |      |
          |      |-Oviraptorinae (not official clade)
          |         |-Citipati osmolskae
          |         |-Citipati sp
          |         |-Oviraptor philoceratops
          |         |-"Oviraptor" mongoliensis
          |         |-Unnamed "spike-crested" form.
          |
          |-?Omnivoropterygidae
             |-Omnivoropteryx sinousaorum

Although the Oviraptorosauria is well known for their bizarre looks, and birdlike appearance,
it's still a very problematic group when it comes to taxonomy. Most of the species are pretty
vague, and they are often confused into each other.

Oviraptorosaurids ranged from 1-3 meters
of lenght and lived in Canada (Caenagnathidae) and eastern Asia (Caenagnathidae, Oviraptidae, Omnivoropteryx) in the late Cretaceous

Their diet was previously thought to be eggs, since a Oviraptor skeleton was found lying
on a nest, but in 1997 Norell et. al. discovered another such nest, with an oviraptorosaurid
(later known as Citipati) lying on top of it. Examination of the nest showed that the eggs
contained tiny oviraptors.
The diet might as well be eggs, but basicly a oviraptorid could eat anything with a strong
shell, like nuts, shellfish and eggs. In the nest of Citipati a small
troodontid skeleton was found - this shows that Oviraptorids probably ate anything that
looked like an easy meal - besides the eggs and shellfish.

Nomingia is a fairly new species, known from bones from the feet, dorsal vertebrae
and ribs, pelvis and tail. The tail is short, and has a primitive pygostyle.

Caenagnathids are the least known of the oviraptorids. Caenagnathasia is only known
from 2 toothless mandibulae, that are elongated, but still looks powerfull.
A new Caenagnathid shows that allso this group presented animals with big crests. Oviraptorinae shares mostly the same features in all species; short tail, long manus, long neck (longer than normally in Maniraptora) and
rounded, sometimes crested, skull - with a deep toothless lower jaw, and bulky palate with 2 teeth.
Currently there is a lot of chaos in the Oviraptoridae family when it comes to keeping the species apart. Oviraptor philoceratops is not the "Oviraptor" we all know with the crest,
it is based only on the AMNH 6517 specimen, which is found without a crest (a crest base is present).
The crested oviraptors we're so familiar with are most likely species of the genus Citipati,
while "Oviraptor" mongoliensis, might as well go back to Rinchenia.

Ingenia has often been portrayed as a crestless Oviraptorid, but is usually
based on Conchoraptor as no skull is known for this species. Only a lower jaw.

Omnivoropteryx is a flying Oviraptorosaur, with features similar to the primitive
Oviraptorosaurids.