Ornithomimidae

Skeleton of Struthiomimus

The Ornithomimidae are a systematic group of dinosaurs within the Ornithomimosauria. There were animals with a slim physique that could probably run fast. Characteristic was the toothless beak, which devoured it, is controversial. The Ornithomimidae are occupied mainly from the Upper Cretaceous of eastern Asia and western North America.

Features

Ornithomimidae were medium-sized representatives of the theropods, they reached a length of 3 to 6 meters.

The skull of Ornithomimidae was elongated and toothless. There was probably a horned beak at the tip of the snout. The head was built relatively small and light, the skull and the muzzle region were pneumatized, ie, with air spaces provided. The eyes were very large and attached to the side of the head, the brain must have been well developed.

The forelimbs were built compared to other theropods relatively large, but delicate. The large hands consisted of three fingers, is characteristic of this group that the three metacarpal bone ( metacarpal ) were approximately equal in length. The fingers showed blunt claws. The hind legs were longer than the front legs, and carried all the weight - like all theropods the Ornithomimidae moved exclusively biped ( with the hind legs ) away. The lower legs were longer than the thigh, which is an indication of fast running. The first toe was missing, the three existing toes were fixed symmetrically to the front. The midfoot was narrow and elongated. A special feature is the arctometatarsale position of these three bones is: the second and fourth touched and pushed the third back so this was just visible at the bottom of the front.

Approximately 72 million year old fossils of a young animal and two adult specimens from Alberta show that Ornithomimus had a downy plumage and the elderly in addition to the fore-arms longer springs possessed that gave their forelimbs a bird wing -like appearance. The late development of the long Vorderarmbefiederung suggests that they probably served the display behavior or the eggs of breeding animals offered additional protection.

Paleobiology

Ornithomimidae were fast runners who could possibly reach the speeds of today's ratites. There are some remains of several animals at the same place, which suggest that they lived together at least temporarily in groups.

What the animals ate is controversial. In spite of belonging to the theropods, they were probably no robbers, speak against the weak hands and the side-mounted eyes. Finds of gastroliths might be an indication for plant food in its beak from Gallimimus discovered lamellae are interpreted as a filtering apparatus with which they seihten small organisms from the water. Even insects as prey or an omnivorous diet have been proposed.

System

The Ornithomimidae together with some primitive representatives ( Pelecanimimus, Shenzhousaurus, Harpymimus and Garudimimus ) the Ornithomimosauria. This ürtümlichen representatives differ in some respects from Ornithomimidae: they have, sometimes even teeth, the first toe is still present and the arctometatarsale position of the metatarsals not pronounced.

The following genera are included among the Ornithomimidae:

Fossils of these animals were found in East Asia and western North America. All originate representatives from the Upper Cretaceous ( Turonian to Maastrichtian ), so are 94-66 million years old.

Mya (unit) Coelurosauria Metacarpus Filter feeder Science (journal) Digital Object Identifier
624035
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