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Avimimus

Avimimus is a small, frail, theropod dinosaur that lived in the Mongolian regions of Asia during the Late Cretaceous Period, about 75 to 85 million years ago. As its name suggests, this dinosaur was very much like a bird, especially an ostrich. Avimimus was very light and could move very quickly and it is possible that its body was covered with feathers. This dinosaur was only 3 feet long and weighed 33 pounds (15 kilograms) but had a remarkable intelligence (measured by the total weight of the brain versus that of the body) relative to other dinosaurs. It was a lightly built animal with long legs.

Description

Avimimus was a dinosaur with a strange appearance. It had a long neck and a short head with a toothless mouth. Its cranial box was large enough, so it is assumed that its brain was too. In place of the teeth, it had a very powerful bill quite comparable to that of the current cockatoos. The bones of the carp were joined as they are in birds, and the three long fingers could be folded under the body. In fact, Avimimus could fully bend its arm against its body in the same way that a bird bends its wings. Its long legs ended in three toes, with a fourth snuggled on the inside of the foot. On the other hand, unlike birds, it had a long bony tail and its pelvis resembled that of other theropods. It is possible that Avimimus had feathers, but the beds in which it was discovered were too rough for such features to be preserved. Nevertheless, a rough edge on its forearm, similar to that of Caudipteryx which supported half of a wing, could serve as an anchor for feathers. Yet it was probably not able to fly.

Diet

The diet of this dinosaur is still under debate. Some researchers believe that Avimimus was an insectivorous animal but others have suggested that it was rather herbivorous. It was able of great speeds, which further improved his predatory ability and protected it from large carnivores. But again, it is just as plausible to think that it was omnivorous and fed mainly on small animals, insects, eggs and plant material. More information is however necessary to determine the exact nature of the eating habits of this little theropod.

Fossils

The original specimens were collected by Russian scientists (Sergei Mikhailovich) during their expedition to Mongolia in the late 1970s and early 1980s, but it was not until 1981 that it was described and named. The initial skeleton was missing a tail, which led us to speculate that Avimimus just did not have one. On the other hand, we have subsequently found remains of caudal vertebra which undeniably confirms the presence of a tail. Initially, the fossils were described as coming from the formation of Djadokhta by the Russian researcher Sergei Kurzanov; however in 2006 colleagues noted that Kurzanov was most likely mistaken and that Avimimus was probably from Nemegt's formation. Since then, Chinese paleontologists have been able to unearth other fossils of partial skeletons and skulls. The most complete skeleton includes a partial skull, vertebrae of the lumbar and cervical region, an incomplete arm, a large part of the hind legs and feet, and part of the pelvis. To date, only four partial skeletons have been discovered; in the Gobi Desert of Mongolia and Alberta in Canada.

Classification

It was originally suggested that Avimimus was a close relative of birds based on these particular characteristics that are so reminiscent of the ostrich. Dr. Kurzanov argued that Avimimus was closer to the direct ancestor of modern birds and that Archaeopteryx was not as close a relative as previously insinuated. However, this thesis is not well defended by phylogenetic analyzes of the relationship between dinosaurs and birds. Most modern scientists agree that Avimimus belongs to a group of dinosaurs that disappeared during the late Cretaceous extinction about 66 million years ago and had characteristics similar to birds but more primitive than Archaeopteryx, the oviraptorosaurs (oviraptorosaurians). In 1981, Kurzanov placed this dinosaur in his own family, the Avimimidae. However, recent studies have shown that Avimimus is better grouped in oviraptorids.

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