Similarities to birds in the structure of the jaws and palate suggest that oviraptorosaurs (oviraptorids and caenagnathids), therizinosauroids, and omithomimosaurs are the closest theropodan relatives of birds, which is in conflict with recent phylogenetic reconstructions based on postcranial evidence. No specific avian similarities could be found in the jaws and palate of dromaeosaurids. The ectopterygoid of the oviraptorids connects the lacrimal to the palatine, as does the avian uncinate (lacrimopalatine). This and other cranial similarities between the oviraptorosaurs and ornithurine birds raise the possibility that oviraptorosaurs are the earliest known flightless birds. With Archaeopteryx and the theropods providing evidence of plesiomorphic conditions, similarities in the mandibles, teeth, and tooth implantation in the Ichthyomithidae and Hesperomithidae may be interpreted as synapomorphies supporting monophyly of the Odontognathae.