Ornithomimosauria
Ornithomimosauria is composed of some basal forms and the
family Ornithomimidae. Ornithomimosaurians are characterized by running adaptations and an eventual loss of teeth.
Their legs, interestingly, are very much like scaled-down versions of
tyrannosauroid legs, suggesting members of both groups were quick.
The members of this group are
characterized by a general physical resemblance to ostriches and other large ground birds.
The average ornithomimosauroid is toothless, has a long neck and short tail,
possesses long but relatively inflexible arms, and has elongated lower legs for rapid
transit. At Ornithomimidae, the members of
this group tend to run together in form, making it difficult to distinguish species and
genera in some cases. It is probable they were at least omnivorous in diet; the hand
structure of the advanced members makes a decent hook, which could have been used for
pulling down tree branches; recent findings of impressions of soft
material in the beak of Gallimimus have suggested structures similar to those of
ducks, indicating a filtering function. Gastroliths were also present in
some, including Sinornithomimus, suggesting a muscular gizzard. If attacked, it is believed they relied on speed for
protection and powerful eyes for detection, as they lack obvious powerful defensive
weapons (besides the odd Deinocheirus). Their tails were
highly-specialized, stiffening towards the end. Their hands were unusual
in that their thumb metacarpal was about as long as their other metacarpals,
unlike most theropods, which had very short thumb metacarpals relative to the
others.
<--Ornithomimosauria
|--Pelecanimimus
`--+--Shenzhousaurus
`--+--Harpymimus
`--+--Garudimimus
`--Ornithomimidae
|--Anserimimus
|--Archaeornithomimus
|--Gallimimus
|--Ornithomimus
`--Struthiomimus
Ornithomimosauria: Note that those here for which we have feet are not arctomets.
| Taxon or Taxa: | Time\Place: | Comments: |
| Pelecanimimus polyodon Perez-Moreno, Sanz, Buscalioni, Moratalla, Ortega, and Rasskin-Gutman, 1994 | late Hauterivian-early Barremian (EK) of Spain | Ironically, this taxon had the most teeth of any known theropod, over 200. These are very small, though. The name derives from skin impressions found with the type that suggest a pelican-like pouch under the throat. The impressions also suggest a soft head crest. These impressions may have been preserved by being covered by a microbial mat. Some researchers have suggested a connection with the spinosaurids, although this looks doubtful. It is based on a partial skeleton (the front chunk, mostly) and skull. |
| Shenzhousaurus orientalis Ji Q., Norell, Makovicky, Gao, Ji.S., and Yuan, 2003 | ?middle Barremian (EK) of China | This is a toothed ornithomimosaurian, with an unmodified hand (the first digit is still shorter than the other two), and more gastroliths, becoming the second ornithomimosaurian reported with such (the first being Sinornithomimus). |
| Harpymimus okladnikovi Barsbold and Perle, 1984 | Barremian-early Aptian (EK) of Mongolia | This ornithomimosaurian still had some teeth in its beak, the hand was unmodified, and it was not an arctomet. It needs a revision, which will no doubt turn up other interesting characters. |
| Garudimimus brevipes Barsbold, 1981 | ?Santonian (LK) of Mongolia | This taxon is known from a partial skull and skeleton. The skull was originally described as possessing a short crest, but this has turned out to have been in error, based on disarticulation. It was not yet a full arctomet. |
Ornithomimosauria i.s.:
| Taxon or Taxa: | Time\Place: | Comments: |
| ?Deinocheirus mirificus Osmolska and Roniewicz, 1970 | early Maastrichtian (LK) of Mongolia | This taxon is based on a shoulder girdle, verts, ribs, and forearms pertaining to a very large animal. The forelimbs themselves measure over 2.4 meters in length. These arms show some resemblance to those of ornithomimosauroids, but are bizarre and basal for that group. |
Ornithomimidae: These animals are pretty much identical in anatomy. Thus,
taxa are often told apart by hand structure, ratios of limb and back length, or by
stratigraphic means (how old they are).
A late Barremian-early Aptian (EK) Japanese vert appears to
come from a very large, early ornithomimid.
| Taxon or Taxa: | Time\Place: | Comments: | |
| Archaeornithomimus asiaticus: Russell, 1972 (originally Ornithomimus asiaticus Gilmore, 1933) | early Maastrichtian (LK) of China | Rather obscure, this basal ornithomimid was for a long period considered a dubious species of Ornithomimus, but later studies and new material have separated the two. | |
| Anserimimus planinychus Barsbold, 1988 | early Maastrichtian (LK) of Mongolia | Based on a partial postcranium, the most interesting thing about this animal is its hands. The metacarpals are bound closely together and the unguals (fingertip bones) are almost hoof-like. What it did with its strange hands is not known. | |
| Gallimimus: Osmólska, Roniewicz, and Barsbold, 1972 | G. bullatus (type) Osmólska, Roniewicz, and Barsbold, 1972 | early Maastrichtian (LK) of Mongolia | Another Nemegt Formation ornithomimid, this taxon has the twin distinctions of being the largest known ornithomimid and of having been in Jurassic Park. Since then, none of the other ornithomimids will speak with it. |
| G. mongoliensis Kobayashi and Barsbold, 2006 | ?Santonian (LK) of Mongolia | G. mongoliensis was floating around as a nomen nudum for a while. It reportedly comes from the same area as Garudimimus, and is based on a nearly complete skeleton (which I saw on display when I went to Mongolia). | |
| Ornithomimus: Marsh, 1890 | O. velox (type) Marsh, 1890 | late Maastrichtian (LK) of Colorado, Utah, and N. Dakota | Ironically, the founding member of the entire Ornithomimidae is also one of its least understood members, due to sparse remains. |
| O. brevitertius Russell, 1972 (originally Struthiomimus brevitertius Parks, 1926; including S. currelli Parks, 1933; S. ingens Parks, 1933; S. samueli Parks, 1928; and Ornithomimus edmontonicus Sternberg, 1933) |
late middle Campanian-early Maastrichtian (LK) of Alberta | Based on remains originally assigned to Struthiomimus,
this species probably relied on its large eyes and brains for
protection. It is best known as Dromiceiomimus, possibly
the fastest classic theropod
that we know of. I'm going to be a twit here. The relevant chapter in the second edition of The Dinosauria refers both species of Dromiceiomimus to Ornithomimus edmontonicus. This is in itself not a bad idea. However, O. edmontonicus is clearly not the oldest available name, so O. brevitertius should be used. So, I'm referring O. edmontonicus and D. samueli to O. brevitertius, the oldest species name of the three. Additionally, Ornithomimus velox isn't all that well-known (or if it is, this fact has been well-hidden from me), so there is the potential to reintroduce Dromiceiomimus. Much better known than O. velox, O. edmontonicus (sometimes incorrectly referred to as O. edmontonensis) is known from a skull and several partial postcranial skeletons. Based on remains once assigned to Struthiomimus, samueli was regarded as very close to the ancestry of O. brevitertius, and could certainly be resurrected (and I tend to lean toward such things on stratigraphic grounds, although good luck trying to find much of a morphological difference). |
|
| Struthiomimus altus Osborn, 1917 (originally Ornithomimus altus Lambe, 1902) (?Ornithomimus) | late middle Campanian-early Maastrichtian (LK) of Alberta | The best-known member of Ornithomimidae to laypeople after Gallimimus (usually as reconstructions under the guise of Ornithomimus), Struthiomimus is sometimes confused with Ornithomimus, its close cousin. It is known from an excellent skeleton, although the skull isn't so well known. | |
Ornithomimidae i.s.:
| Taxon or Taxa: | Time\Place: | Comments: |
| "Archaeornithomimus" bissektensis (N.D.) Nessov, 1995 | Coniacian (LK) of Uzbekistan | This possible ornithomimid is based on metatarsals, but Archaeornithomimus has got enough problems of its own without referring fragmentary taxa to it. |
| "Coelosaurus" antiquus (N.D.) Leidy, 1865 | Campanian-Maastrichtian (LK) of New Jersey, North Carolina, and Alabama | While the remains here pertain to an indeterminate ornithomimid, the distribution shows that ornithomimids lived in the eastern and southern US during the LK. The remains are sometimes referred to other, better-known ornithomimids. |
| ?"Ginnareemimus"
[no species name] (N.N.) Kaneko, 2000 |
?Valanginian-?Hauterivian (EK) of Thailand | Possibly the oldest ornithomimid, "Ginnareemimus" is based on some vertebrae and a third metatarsal with the distinctive pinch of an arctomet. |
| "Orcomimus" (N.N.) Triebold, 1997 | late Maastrichtian (LK) of South Dakota | Another undescribed apparently basal ornithomimid, little is known about this one yet. It is from the Sandy site (home of the pachycephalosaurid that looks like Stygimoloch if you look at it one way and Pachycephalosaurus if you look at it another way), and is based on a hindlimb and pelvis. |
| "Ornithomimus" sedens (N.D.) Marsh, 1892 | late Maastrichtian (LK) of Wyoming | This is an indeterminate ornithomimid, based on a sacrum (hip verts) and ilium. There is a good skeleton going under the name of Struthiomimus sedens, although on what grounds I don't know, besides that being the only species previously named from the vicinity. |
| Sinornithomimus dongi Kobayashi and Lu, 2003 | early LK of China | Sinornithomimus is the "gastrolith" ornithomimid. It is known from the remains of at least fourteen individuals found in a small space, eleven of which are apparently juveniles, suggesting gregarious behavior. It is a moderately basal ornithomimid, with a short neck. |
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