Ornithomimus (; "bird mimic") is a genus of ornithomimid theropod dinosaurs from the Campanian and Maastrichtian ages of the Late Cretaceous in western North America. Ornithomimus was a swift, bipedal dinosaur which was covered in feathers and equipped with a small toothless beak that may indicate an omnivorous diet. It is usually classified into two species: the type species, Ornithomimus velox, and a referred species, Ornithomimus edmontonicus.
O. velox was named in 1890 by Othniel Charles Marsh on the basis of a foot and partial hand from the Denver Formation of Colorado. Other seventeen species have been named since then, though almost all of them have been subsequently assigned to new genera or shown not to be directly related to O. velox. The best material of species still considered part of the genus has been found in Alberta, representing the species O. edmontonicus, known from several skeletons from the Horseshoe Canyon Formation. Additional species and specimens from other formations are sometimes classified in the genus, such as Ornithomimus samueli (alternatively classified in the genera Dromiceiomimus or Struthiomimus) from the earlier Dinosaur Park Formation.
History of discovery First species named
The history of Ornithomimus classification and the classification of ornithomimids in general has been very complicated. The type species, Ornithomimus velox, was first named by O.C. Marsh in 1890 and is based on syntypes YPM 542 and YPM 548 (a partial hindlimb and forelimb, respectively), found by George Lyman Cannon in the Denver Formation of Colorado on June 30, 1889. The generic name means "bird mimic", derived from Greek words ὄρνις (ornis), "bird", and μῖμος (mimos), "mimic", in reference to the bird-like foot. The specific name means "swift" in Latin.O.C. Marsh, 1890, "Description of new dinosaurian reptiles", The American Journal of Science, series 3 39: 81-86 Simultaneously, Marsh named two other species: Ornithomimus tenuis (based on specimen USNM 5814) and Ornithomimus grandis. Both consist of fragmentary fossils found by John Bell Hatcher in Montana, which is today understood as tyrannosauroid material. At first, Marsh assumed Ornithomimus was an ornithopod, but this changed when Hatcher and A. E. Sullins found the specimen USNM 4736, a partial ornithomimid skeleton, in 1891 from the Lance Formation of Wyoming. Marsh named it Ornithomimus sedens in 1892, though the specimen remained unnumbered and not figured until Charles Whitney Gilmore's 1920 re-description. Marsh also named Ornithomimus minutus was also created based on the specimen YPM 1049 (a metatarsus) in 1892,O.C. Marsh, 1892, "Notice of new reptiles from the Laramie Formation", American Journal of Science 43: 449-453 but it has since been recognized as belonging to an alvarezsaurid.Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.
A sixth species, Ornithomimus altus, was named in 1902 by Lawrence Lambe and was based on specimen CMN 930 (hindlimbs found in 1901 in Alberta),Lambe, L., 1902, "New genera and species from the Belly River Series (mid-Cretaceous)", Geological Survey of Canada Contributions to Canadian Palaeontology 3(2): 25-81 but this was renamed to a separate genus in 1916: Struthiomimus, by Henry Fairfield Osborn.H.F. Osborn, 1916, "Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus", Bulletin of the American Museum of Natural History 35(43): 733-771 In 1920, Gilmore named Ornithomimus affinis for Dryosaurus grandis (Lull 1911), based on indeterminate material. In 1930, Loris Russell renamed Struthiomimus brevetertius (Parks 1926) and Struthiomimus samueli (Parks 1928) into Ornithomimus brevitertius and Ornithomimus samueli, respectively.Russell, L.S., 1930, "Upper Cretaceous dinosaur faunas of North America", Proceedings of the American Philosophical Society, 69(4): 133-159 The very same year, Oliver Perry Hay renamed Aublysodon mirandus (Leidy 1868) into Ornithomimus mirandus,Hay, O.P., 1930, Second Bibliography and Catalogue of the Fossil Vertebrata of North America. Carnegie Institution of Washington. 390(II): 1-1074 which is today seen as a nomen dubium. In 1933, William Arthur Parks created the species Ornithomimus elegans,Parks, W.A., 1933, "New species of dinosaurs and turtles from the Upper Cretaceous formations of Alberta", University of Toronto Studies, Geological Series, 34: 1-33 which is today seen as either Chirostenotes or Elmisaurus. That same year, Gilmore named Ornithomimus asiaticus for material found in Inner Mongolia.Gilmore, C.W., 1933, "On the dinosaurian fauna of the Iren Dabasu Formation", Bulletin of the American Museum of Natural History, 67: 23-78
Also in 1933, Charles Mortram Sternberg named the species Ornithomimus edmontonicus for a nearly complete skeleton from the Horseshoe Canyon Formation (specimen CMN 8632).Sternberg, C.M., 1933, "A new Ornithomimus with complete abdominal cuirass", The Canadian Field-Naturalist 47(5): 79-83
Reclassification by Dale Russell
At first, it had been common practice to name each newly discovered ornithomimid as a species of Ornithomimus. In the sixties, this tendency was still very strong, as is shown by the fact that Oskar Kuhn renamed Megalosaurus lonzeensis (Dollo 1903) from Belgium into Ornithomimus lonzeensis (which is understood today to be an abelisauroid claw)Kuhn, O., 1965, "Saurischia (Supplementum 1)". In: Fossilium Catalogus 1. Animalia. 109: 1-94 and Dale Russell in 1967 renamed Struthiomimus currellii (Parks 1933) and Struthiomimus ingens (Parks 1933) into Ornithomimus currellii and Ornithomimus ingens, respectively.Russell, D.A. and Chamney, T.P., 1967, "Notes on the biostratigraphy of dinosaurian and microfossil faunas in the Edmonton Formation (Cretaceous), Alberta", National Museum of Canada Natural History Papers, 35: 1-22 At the same time, it was usual that workers referred to the entire ornithomimid material as simply "Struthiomimus".Norman, D., 1985, The Illustrated Encyclopedia of Dinosaurs, Crescent Books, New York, p. 48 To solve this confusion by scientifically testing the separation between Ornithomimus and Struthiomimus, Dale Russell in 1972 published a morphometric study. It showed that statistical differences in some proportions could be used to distinguish the two and he concluded that Struthiomimus and Ornithomimus were valid genera. In the latter, Russell recognised two species: the type species Ornithomimus velox and Ornithomimus edmontonicus (even though he had trouble reliably distinguishing it from O. velox). He considered Struthiomimus currellii to be a younger synonym of Ornithomimus edmontonicus. However, Russell also interpreted the data as indicating that many specimens could not be referred to either Ornithomimus or Struthiomimus. Therefore, he created two new genera. The first one was Archaeornithomimus. Ornithomimus asiaticus and Ornithomimus affinis were reassigned to this new genus, becoming Archaeornithomimus asiaticus and Archaeornithomimus affinis. The second one was Dromiceiomimus, meaning "Emu mimic". This comes from the old generic name for the emu: Dromiceius. Russell assigned several former Ornithomimus species named during the 20th century, including O. brevitertius and O. ingens, to this new genus as Dromiceiomimus brevitertius. He also renamed Ornithomimus samueli into a second Dromiceiomimus species: Dromiceiomimus samueli.Russell, D. (1972). "Ostrich dinosaurs from the Late Cretaceous of western Canada." Canadian Journal of Earth Sciences, 9: 375-402.
Misassigned to Ornithomimus Two tibiae from the Navesink Formation of New Jersey were named Coelosaurus antiquus ("antique hollow lizard") by Joseph Leidy in 1865. The tibiae were first attributed to Ornithomimus in 1979 by Donald Baird and John R. Horner as Ornithomimus antiquus.Baird D., and Horner, J., 1979, "Cretaceous dinosaurs of North Carolina", Brimleyana 2: 1-28 Normally, this would have made Ornithomimus a junior synonym of Coelosaurus, but Baird and Horner discovered that the name "Coelosaurus" was preoccupied by a dubious taxon, which was based on a single vertebra. It was originally named Coelosaurus by an anonymous author now known to be Richard Owen in 1854. Baird referred several other specimens from New Jersey and Maryland to O. antiquus. Beginning in 1997, Robert M. Sullivan regarded O. velox and O. edmontonicus as junior synonyms of O. antiquus. Like Russell, he considered the former two species indistinguishable from each other and noted that they both shared distinctive features with O. antiquus.Sullivan, (1997). "A juvenile Ornithomimus antiquus (Dinosauria: Theropoda: Ornithomimosauria), from the Upper Cretaceous Kirtland Formation (De-na-zin Member), San Juan Basin, New Mexico." New Mexico Geological Society Guidebook, 48th Field Conference, Mesozoic Geology and Paleontology of the Four Corners Region. 249-254. However, David Weishampel (2004) considered "C." antiquus to be indeterminate among ornithomimosaurs, resulting in it being a nomen dubium.Weishampel, D.B.(2004). "Another Look at the Dinosaurs of the East Coast of North America. En (Colectivo Arqueológico-Paleontológico Salense, Ed.). " Actas de las III Jornadas sobre Dinosaurios y su Entorno. 129-168. Salas de los Infantes, Burgos, España. An SVP 2012 abstract agreed with Weishampel by noting that Coelosaurus differs from Gallimimus and Ornithomimus in the features of the tibiae.Brusatte, Choiniere, Benson, Carr and Norell, 2012. Theropod dinosaurs from the Late Cretaceous of Eastern North America: Anatomy, systematics, biogeography and new information from historic specimens. Journal of Vertebrate Paleontology. Program and Abstracts 2012, 70.
In 1988, Gregory S. Paul classified the various species of Archaeornithomimus, Struthiomimus, Dromiceiomimus, and Gallimimus to the genus Ornithomimus.Paul, G.S., 1988, Predatory Dinosaurs of the World. Simon & Schuster: New York. 464 pp This has found no acceptance among other workers and the name is not presently used by Paul himself.
Present interpretations
Even after Russell's study, various researchers have found reasons to lump some or all of these species back into Ornithomimus in various combinations. In 2004, Peter Makovicky, Yoshitsugu Kobayashi, and Phil Currie studied Russell's 1972 proportional statistics to re-analyze ornithomimid relationships in light of newly discovered specimens. They concluded that there was no justification to separate Dromiceiomimus from Ornithomimus, sinking Dromiceiomimus as a synonym of O. edmontonicus.Makovicky, Kobayashi and Currie (2004). "Ornithomimosauria." In Weishampel, Dodson and Osmolska (eds.), The Dinosauria Second Edition. University of California Press. 861 pp. However, they did not include the type species O. velox in this analysis. The same team further supported the synonymy between Dromiceiomimus and O. edmontonicus in a 2006 lecture at the Society of Vertebrate Paleontology annual meeting.Kobayashi, Makovicky and Currie (2006). "Ornithomimids (Theropoda: Dinosauria) from the Late Cretaceous of Alberta, Canada." Journal of Vertebrate Paleontology, 26(3): 86A. Their opinion has been followed by most later authors. Makovicky's team also considered Dromiceiomimus samueli to be a junior synonym of O. edmontonicus, though Longrich later suggested it may belong to a distinct, unnamed species from the Dinosaur Park Formation which has yet to be described. Longrich called the species Ornithomimus samueli in a faunal list for the Dinosaur Park Formation.