O

Ohmdenosaurus Wild, 1978
    type species: O. liasicus Wild, 1978
Ojoceratops Sullivan and Lucas, 2010
    type species: O. fowleri Sullivan and Lucas, 2010
Oligosaurus (N.D.) Seeley, 1881=Rhabdodon
   type species: O. adelus (N.D.) Seeley, 1881=Rhabdodon priscus
Olorotitan Godefroit, Bolotsky, and Alifanov, 2003
    type species: O. arharensis Godefroit et al., 2003
Omeisaurus Yang, 1939
    type species: O. junghsiensis Yang, 1939
    other species: ?"O. zizongensis" (N.N.) Tanimoto, 1988
                         O. fuxiensis (Hou, Chao, and Chu, 1976 (originally Zigongosaurus))=Zigongosaurus fuxiensis
                         O. fuxiensis Dong, Zhou, and Zhang, 1983=?"O." changshouensis
                         "O. gongjianensis" (N.N.) Zhang and Wei, 1995="Mamenchisaurus gongjianensis"
                         "O." changshouensis Yang, 1958>Sauropoda incertae sedis
                         "O." luoquanensis Li, 1988>Sauropoda incertae sedis
                         "O." maoianus Tang, Jin, Kang, and Zhang, 2001>Sauropoda incertae sedis
                         "O." tianfuensis He, Li, Cai, and Gao, 1984>Eusauropoda
Omnivoropteryx Czerkas and Ji, 2002
    type species: O. sinousaorum, Czerkas and Ji, 2002
Omosaurus Owen, 1875/Leidy, 1856=Dacentrurus
   "type species": "O." armatus Owen, 1875=Dacentrurus armatus
   other species: "O." durobrivensis (N.D.) Hulke, 1887>Stegosauria incertae sedis
                         "O." hastiger (N.D.) Owen, 1877>Thyreophora incertae sedis
                         "O." leedsi (N.D.) Seeley vide Huene, 1901>Stegosauridae incertae sedis
                         "O." lennieri (N.D.) Nopcsa, 1911=Dacentrurus armatus
                         "O." phillipsi (N.D.) Seeley, 1893>Dinosauria incertae sedis
                         "O." vetustus (N.D.) Huene, 1910>Dinosauria incertae sedis
Onychosaurus (N.D.) Nopcsa, 1902
   type species: O. hungaricus (N.D.) Nopcsa, 1902
Opisthocoelicaudia Borsuk-Bialynicka, 1977
    type species: O. skarzynskii Borsuk-Bialynicka, 1977
Oplosaurus (?N.D.) Gervais, 1852
    type species: O. armatus (?N.D.) Gervais, 1852
"Orcomimus" (N.N.) Triebold, 1997
Orinosaurus (N.D.) Lydekker, 1889=Orosaurus
   type species: O. capensis (N.D.) Lydekker, 1889=O. capensis
Orkoraptor Novas, Ezcurra, and Lecuona, 2008
    type species: O. burkei Novas et al., 2008
Ornatotholus (N.D.) Galton and Sues, 1983="Stegoceras"
    type species: O. browni (N.D.) (Wall and Galton, 1979 (originally Stegoceras))="S." browni
"Ornithocheirus" hilesnis (N.D.) Koken, 1885>Theropoda incertae sedis
Ornithodesmus (N.D.) Seeley, 1887
    type species: O. cluniculus (N.D.) Seeley, 1887
    other species: O. latidens Seeley, 1901>Pterosauria (Istiodactylus latidens)
"Ornithoides" (N.N.) Osborn, 1924=Saurornithoides
   "type species": "O. oshiensis" (N.N.) Osborn, 1924=Saurornithoides mongoliensis
Ornitholestes Osborn, 1903
    type species: O. hermanni Osborn, 1903
Ornithomerus (N.D.) Seeley, 1881=Rhabdodon
   type species: O. gracilis (N.D.) Seeley, 1881=Rhabdodon priscus
Ornithomimidorum (N.O.) Huene, 1926="Megalosaurus"
    "type species": O. genus a lonzeensis (N.O.) (Dollo, 1883 (originally Megalosaurus))="M." lonzeensis
   "other species": O. genus b bredai (N.O.) (Seeley, 1883 (originally Megalosaurus))="M." bredai
Ornithomimoides (N.D.) Huene and Matley, 1933
    type species: O. barasimlensis (N.D.) Huene and Matley, 1933
    other species: "O." mobilis (N.D.) Huene and Matley, 1933>Abelisauroidea incertae sedis
Ornithomimus Marsh, 1890
    type species: O. velox Marsh, 1890
    other species: O. brevitertius (Parks, 1926 (originally Struthiomimus))
                         O. affinis (N.D.) Gilmore, 1920="Dryosaurus" grandis
                         O. altus Lambe, 1902=Struthiomimus altus
                         O. antiquus (N.D.) (Leidy, 1865 (originally Coelosaurus))="C." antiquus
                         O. asiaticus Gilmore, 1933=Archaeornithomimus asiaticus
                         O. bullatus (Osmólska, Roniewicz and Barsbold, 1972 (originally Gallimimus))=Gallimimus bullatus
                         O. edmontonensis Barsbold and Osmólska, 1990=O. brevitertius
                         O. edmontonicus Sternberg, 1933=O. brevitertius
                         O. elegans Parks, 1933=Elmisaurus elegans
                         O. lonzeensis (N.D.) (Dollo, 1883 (orignally Megalosaurus))="M." lonzeensis
                         O. samueli (Parks, 1928 (originally Struthiomimus))=O. brevitertius
                         "O." grandis (N.D.) Marsh, 1890>Tyrannosauridae incertae sedis
                         "O." minutus (N.D.) Marsh, 1892>Tyrannoraptora incertae sedis
                         "O." sedens (N.D.) Marsh, 1892>Ornithomimidae incertae sedis
                         "O." tenuis (N.D.) Marsh, 1890>Tyrannoraptora incertae sedis
Ornithopsis (N.D.) Seeley, 1870
    type species: O. hulkei (N.D.) Seeley, 1870
    other species: O. manseli (N.D.) (Hulke, 1874 vide Lydekker, 1888 (originally Ischyrosaurus))="Ischyrosaurus" manseli
                          "O." eucamerotus (N.D.) Hulke, 1882>Sauropoda incertae sedis
                          "O." greppini (?N.D.) Huene, 1922>Sauropoda incertae sedis
                          "O." leedsi (N.D.) Hulke, 1887>Sauropoda incertae sedis
Ornithotarsus (N.D.) Cope, 1869
    type species: O. immanis (N.D.) Cope, 1869
Orodromeus Horner and Weishampel, 1988
    type species: O. makelai Horner and Weishampel, 1988
    other species: O. minimus (N.D.) (Gilmore, 1924 (originally Laosaurus))="Laosaurus" minimus
Orosaurus Huxley, 1867 (N.D.)
   type species: O. capensis (N.D.) (Lydekker, 1889 (originally Orinosaurus))
Orthogoniosaurus (N.D.) Das-Gupta, 1931
    type species: O. matleyi (N.D.) Das-Gupta, 1931
Orthomerus (N.D.) Seeley, 1883
    type species: O. dolloi (N.D.) Seeley, 1883
    other species: "O." weberi (N.D.) Riabinin, 1945>Hadrosauridae incertae sedis
Oryctodromeus Varricchio, Martin, and Katsura, 2007
    type species: O. cubicularis Varricchio et al., 2007
"Oshanosaurus" (N.N.) Zhao, 1986
    "type species": "O. youngi" (N.N.) Zhao, 1986
Othnielia Galton, 1977="Nanosaurus"
    type species: O. rex (Marsh, 1877 (originally Nanosaurus))="Nanosaurus" rex
    other species: O. consors (Marsh, 1894 (originally Laosaurus))=Othnielosaurus consors
                         O. minimus (N.D.) (Gilmore, 1924 (originally Laosaurus))=Orodromeus minimus
                         O. multidens (He and Cai, 1983 (originally Yandusaurus))=Hexinlusaurus multidens
                         O. nisti (Bakker, Galton, Siegwarth, and Filla, 1990 (originally Drinker))=Drinker nisti
Othnielosaurus Galton, 2006
    type species: O. consors (Marsh, 1894 (originally Laosaurus))
"Otogosaurus sarulai" (N.N.) Unofficially-named sauropod, possibly Zhao, 2004, Camp-Mass of China
Ouranosaurus Taquet, 1976
    type species: O. nigeriensis Taquet, 1976
Oviraptor Osborn, 1924
    type species: O. philoceratops Osborn, 1924
    other species: O. mongoliensis Barsbold, 1986=Rinchenia mongoliensis
                         O. yanshini (Barsbold, 1981 (originally Ingenia))=Ingenia yanshini
"Ovoraptor" (N.N.) Osborn, 1924=Velociraptor
   "type species": "O. djadochtari" (N.N.) Osborn, 1924=Velociraptor mongoliensis
Owenodon Galton, 2009
    type species: O. hoggii (Newton, 1892 (originally Iguanodon))
Ozraptor (?N.D.) Long and Molnar, 1998
    type species: O. subotaii (?N.D.) Long and Molnar, 1998