SUMMARY AND CONCLUSION
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发布时间：2022-07-13 05:52
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时间：2023-10-25 04:18
The members of Oviraptoridae are mainly known from the Late Cretaceous of the Gobi region.Seven genera（Oviraptor，Ingenia，Conchoraptor，Nomingia，Citipati，Khaan，and Nemegtia）are from Mongolia（Osborn，1924；Barsbold，1981；Barsbold et al.，1990；Clark et al.，2001；Lü et al.，2004）.One specimen with a nest but incomplete skeleton was found in Inner Mongolia，People's Republic of China（Dong&Currie，1996）.Heyuannia huangi（Lü，2003）from the Heyuan Basin and two new specimens from the Nanxiong Basin are from southern China.Southern China is becoming important as a source for new oviraptorid material.Oviraptorid dinosaurs were found at four localities（Dongyuan and Huangsha，Heyuan City；and Shixing and Xincheng District，Nanxiong Basin）in southern China.They occur in three different horizons.
The present phylogenetic analysis places the Alvarezsauridae as either the sister group to TO（Therizinosauroidea and Oviraptorosauria）（Fig.18），or sister group to Oviraptorosauria（Fig.27），which is incongruent with the results of Hwang et al.（2002；2004）.The interrelationships of oviraptorosaurs are explored.The primitive forms，such as Incisivosaurus gauthieri，Caudipteryx zoui，Microvenator celer，and Avimimus portentosus form an ascending sequence from most primitive to more derived in the strict consensus tree（Fig.36）.Caenagnathidae are more derived than Avimimus portensus，but basal to Oviraptoridae.Two subgroups of Oviraptoridae（Oviraptorinae and Ingeniinae）are shown in the tree in agreement with Barsbold's（1981）classification.Heyuannia huangi is basal to Ingeniinae.Two new oviraptorid dinosaurs from the Nanxiong Basin are nested in different groups.The phylogenetic analysis indicates that all oviraptorosaurs form a monophyletic group，but it does not show that they fall within Aves，in contrast to the results of Maryańska et al.（2002）and Lü et al.（2002），which regarded oviraptorosaurs as flightless birds.However，the derived oviraptorids（Maryańska&Osmólska，1997）and Heyuannia huangi，indeed independently attained more avian characters（especially ratite-like characters）than other groups of theropods.They demonstrate an excellent case of convergent evolution.These characters include：quadrate is a single headed but with two clear articular surfaces；pneumatic quadrate；rod-like jugal bar；uncinate process；U-shaped furcula；movable articulation between the quadrate and quadratojugal；ischium does not have symphysis；blunt angle between scapula and coracoid；pubis is rod-like，as that of Diatryma steini（Matthew&Granger，1917）and Phororhacos inflatus（Andrews，1901）；decurved tip of the upper jaw，when closed，the upper jaw projects far anteriorly from the lower jaw；preserved angle between the manus and the forearm is less than 90°.The derived oviraptorosaurs also independently acquired the following characters，which are similar to Archaeopteryx lithographica（Elzanowski，2002）：boomerang-shaped furcula，with a hypocleideum and a more rounded cross-section；fused scapula-coracoid；premaxilla projects beyond the tip of the mandible；the configuration of the quadrate；vomers fused into a single bone；distal end of the scapula slightly expanded；no indication of either external or internal tuberosity on the humerus；semilunate bone articulates with the metacarpal Ⅰ and metacarpal Ⅱ，not with metacarpal Ⅲ.Other avian characters，such as more than 8 sacral vertebrae，ilia approaching at midline and the large pneumatic opening on femur，also present in some derived oviraptorosaurs.
Several groups of Maniraptora independently acquired avian characters.In the Dromaeosauridae，some small sized indivials acquired flight feathers such as Microraptor gui.These feathers are distributed on both the front and hind limbs，perhaps making it possible to glide among the trees（Xu et al.，2003）.Alvarezsauridae have a relatively large body sizes，but they acquired many avian characters in their skulls as mentioned above.The derived oviraptorosaurs acquired the most avian characters.
The synapomorphies supporting Oviraptorosauria are：distal end of paroccipital process curves ventrally，pendant；retroarticular process is elongate and slender；coronoid ossification is only a thin splint；preorbital skull length to basal skull length ratio is 0.5 or less；subantorbital portion of the maxilla inset medially；ventral margin of the external naris is dorsal to the maxilla；accessory process for contact with the quadratojugal is on the distal end of the quadrate；ectopterygoid situated rostral to the pterygoid；massive longitudinal pterygoid-ectopterygoid present；extended shelf at the mandibular symphysis is present；mandibular rami in dorsal view are bowed laterally at mid-length；long and shallow caudoventral process of the dentary，extending caudally at least to the caudal border of the external mandibular fenestra is present；mandibular articular facet for the quadrate is formed exclusively of the articular；and the articular facet for the mandibular joint positioned above the dorsal margin of the caudal part of the mandibular ramus.
