Alvarezsauridae

Graphical live reconstruction of Mononykus

• Asia
• North America
• South America

The Alvarezsauridae are a kinship group ( taxon ) theropod dinosaur bird similar within the Coelurosauria. They lived from the Upper Jurassic to Upper Cretaceous in Asia, North and South America, may they also occurred in Australia and Europe.

Features

The Alvarezsauriden were slim and long-legged animals that were one -half to two feet long. The front legs were very short but strong. A finger, the thumb is, greatly enlarged and provided with a sharp claw, the other two fingers are reduced to tiny remnants. It is believed among other things that the front legs for digging to countries forming insects, such as termites, were used. The Alvarezsauridae have in common a number of characteristics with the birds. So her little chest (sternum ) is provided with a sternal bar that magnifies the approach surface for the muscles of the forelimbs. As with the birds are with them carpal and metacarpal bones fused ( Carpometacarpus ). In Shuvuuia spring-like structures were observed.

System

The Alvarezsauridae were originally assigned very close to the birds, such as the sister group of Archaeopteryx. This idea was, however, of but later discovered primitive forms as Haplocheirus, Patagonykus and Alvarezsaurus into perspective, does not show all the bird-like features of the first discovered species Mononykus and Shuvuuia. The corresponding features could be in birds and the late Alvarezsauriden therefore also independent ( convergent ) have evolved from each other.

The systematic position of the Alvarezsauridae is still controversial and the subject of controversial debate. They are placed within the Coelurosauria to the Maniraptora or as a sister group of the Ornithomimosauria to Ornithomimiformes.

• Alvarezsauroidea Haplocheirus
• Alvarezsauridae Kol
• Alvarezsaurus
• Patagonykus
• Achillesaurus
• Albertonykus
• Mononykinae Heptasteornis
• Mononykus
• Shuvuuia
• Parvicursor