Ornithomimosauria
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Ornithomimosaurs ('Bird mimic lizards') or members of the clade Ornithomimosauria are theropod dinosaurs, like Gallimimus, which bore a superficial resemblance to modern ostriches. They were fast, fleet-footed, omnivorous and herbivorous dinosaurs from the Upper Cretaceous Period of Laurasia (now Asia, Europe and North America). The skull, sitting atop a long neck, was relatively small, with large eyes. Some primitive species had teeth but most had toothless beaks.
The fore limbs ('arms') were long and slender and bore powerful claws. The hind limbs were long and powerful, with a long foot and short, strong toes terminating in hooflike claws. Ornithomimosaurs were probably among the fastest of all dinosaurs. Like many other coelurosaurs, the ornithomimid hide was probably feathered rather than scaly.
The group first appeared in the Lower Cretaceous and persisted until the Upper Cretaceous. They appear to be related to less-derived coelurosaurian theropods such as Compsognathus and tyrannosaurids. Primitive members of the group include Pelecanimimus, Shenzhousaurus, Harpymimus and probably the huge Deinocheirus, the arms of which reached eight feet in length. More advanced species, members of the family ornithomimidae, include Gallimimus, Archaeornithomimus, Anserimimus, Struthiomimus, and Ornithomimus.
Ornithomimosaurs probably acquired most of their calories from plants but may have eaten small vertebrates and insects as well. Henry Fairfield Osborn suggested that the long, sloth-like 'arms' may have been used to pull down branches on which to feed. They may also have constituted a dangerous weapon. The sheer abundance of ornithomimids — they are the most common small dinosaurs in North America — is consistent with the idea that they were plant eaters, as herbivores usually outnumber carnivores in an ecosystem. The presence of gastroliths in the stomach of some ornithomimids fit this hypothesis.
Some paleontologists, like Paul Sereno, consider the enigmatic alvarezsaurids to be close relatives of the ornithomimosaurs and places them together in the superfamily Ornithomimoidea (see classification below).
[edit] Classification
The group Ornithomimiformes is defined by Sereno (2005) as (Ornithomimus velox > Passer domesticus) and is useful in classification, only if alvarezsaurids or some other group are actually close relatives of ornithomimosaurs. The Ornithomimosauria is an inclusive clade that contains primitive ornithomimosaurs and ornithomimids proper. The most advanced ornithomimids belong to the subfamily ornithomiminae.
- Ornithomimiformes
- ORNITHOMIMOSAURIA
- Pelecanimimus (central Spain)
- Family Harpymimidae
- Shenzhousaurus (Liaoning, Northeastern China)
- Family Deinocheiridae
- Family Ornithomimidae
- Subfamily Garudimiminae
- Subfamily Ornithomiminae
- Sinornithomimus (Inner Mongolia, China)
- Archaeornithomimus (China)
- Gallimimus (Mongolia)
- Struthiomimus (Montana and Alberta in North America)
- Dromiceiomimus (Alberta, Canada)
- Ornithomimus (Colorado and Alberta in North America)
- Anserimimus (Mongolia)
- ORNITHOMIMOSAURIA
[edit] Other evidence
Note that, Timimus, early Cretaceous fossil remains (a femur) from Dinosaur Cove in Victoria in southeastern Australia are possibly ornithomimosaurian.
[edit] External links
- A Guide to Ornithomimosauria with pictures
- Khalaf-von Jaffa, Norman Ali Bassam Ali Taher (2006). Ornithomimid Dinosaur Tracks from Beit Zeit, West of Jerusalem, Palestine.Gazelle: The Palestinian Biological Bulletin. Number 56, August 2006. pp. 1-7.
