Palaeos		Coelurosauria
Vertebrates		Ornithomimosauria

Coelurosauria: Ornithomimosauria

Ornithomimus

DINSAUROMORPHA
|--ORNITHISCHIA
`--+--SAUROPODOMORPHA
   `--THEROPODA
      |
      `--COELUROSAURIA
               |--Tyrannosauroidea 
               `--+--Coelurus 
                   `--Maniraptoriformes
                      |--Ornithomimosauria
                      `--Maniraptora
                         |--Therizinosauroidea
                         `--+--Alvarezsauridae
                            `--+--Oviraptorosauria
                               `--+--+--Troodontidae
                                  |   `--Dromaeosauridae
                                  `--AVES

Taxa on this Page

1. Ornithomimosauria X

Descriptions

Ornithomimosauria: Ornithomimus, Gallimimus. Used here as Ornithomimus > real birds (i.e. = Arctometatarsalia)

Range: Early to Late Cretaceous of Europe & North America.

Phylogeny: Maniraptoriformes : (Ornitholestes + Maniraptora) + *. 

Characters: Gracile, cursorial, with (moderately?) long neck and tail; $ enlarged, beak-like premaxilla; premaxilla with long posterior process separating maxilla from nasal [H+01]; long, shallow snout formed dorsally by elongated nasal; nares at tip of snout between premaxilla and nasal; elongated antorbital fossa with 2-3 fenestrae; very large orbits; bone capsule of unknown function at base of braincase; braincase and overlying frontals are strongly domed, sloping forward smoothly on the frontals and nasals and back sharply on parietals; postorbital skull short; squamosal with pneumatic recess [H00*]; lower temporal fenestra reduced; in derived species, quadrate slopes anteroventrally, lower jaw is offset anteriorly and articulates below the orbit (which might just explain the mystery capsule); $ secondary palate created by maxilla and premaxilla; toothless in almost all species; premaxillary teeth incisor-like with both carinae of each tooth being placed along the same plane perpendicular to the main axis of the skull [H00*]; teeth, where present, lack serrations [H+01]; vertebrae 10+13+5-6+<40; caudals moderately elongated, with low spines & short ribs fused to centra; dorsals with taller spines; caudals have transverse processes proximally which apparently retrovert (and articulate?) distally; large pectoral girdle with especially large coracoid bearing posteroventral process & large tubercle for biceps; clavicles unknown & girdle may be mobile; sternum in 1 species.; $ gracile, straight humerus with reduced deltopectoral crest [H+01]; ulna & radius adhere distally; carpals flat, reduced & perhaps could not flex;semilunate carpal block reduced or absent [H00*]; $ long hand; $ metacarpals equal length; $ same for digits; $ unguals straight, with weak flexor tubercles [H+01]; strongly probubic, with pubes fused;semicircular scar on posterior face of ischium {H00*]; tibia elongate [H+01]; $ metatarsus elongated to ~80% length of tibia; $ short, stout pedal digits; pes V absent [$MB89].  

Note:  [1] Ornithomimosaurs are often said to "resemble an ostrich," however the posture was quite different as currently reconstructed. [2] A recent report in Nature (Aug. 30, 2001) announces the discovery of keratinous beak fragments in Gallimimus suggesting a filter-feeding adaptation similar to a duck. [3] There is ongoing debate about whether some species were herbivores. The recent discovery of gastroliths is a strong argument in favor of this idea. [4] Characters ascribed to [H00*] are those which unite ornithomimids and tyrannosaurs.  

Links: DD: Ornithomimosauria; Harpymimus; Garudimimus; Gallimimus; (all 3 from the high-quality Nakasato Museum site); ornithomimosauria cladogram; Gallimimus (life reconstruction); Ornithomimidae; VPTHEROPOD; Ornithomimosauria ; ; Untitled Document (Hungarian). 

References: Holtz (2000) [H00], Hutt et al. (2001) [H+01], Mader & Bradley (1989) [MB89].  ATW 020128.