Alvarezsauridae

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Alvarezsauridae
Graphic reconstruction of the skeleton and outline of Linhenykus monodactylus

Graphic reconstruction of the skeleton and outline of Linhenykus monodactylus

Temporal occurrence
Oxfordium ( Upper Jurassic ) to Maastrichtium ( Upper Cretaceous )
163.5 to 66 million years
Locations
Systematics
Lizard dinosaur (Saurischia)
Theropoda
Coelurosauria
Maniraptora
Alvarezsauroidea
Alvarezsauridae
Scientific name
Alvarezsauridae
Bonaparte , 1991

The Alvarezsauridae are a family group ( taxon ) of bird-like theropod dinosaurs within the Coelurosauria . They lived from the Upper Jurassic to the Upper Cretaceous in Asia , North and South America , and they may also have occurred in Australia and Europe .

features

The Alvarezsauriden were slender and long-legged animals that were half a meter to two meters long. The front legs were very short but strong. One finger, the thumb , is greatly enlarged and has a sharp claw, the other two fingers are reduced to tiny remains. It is believed, among other things, that the front legs were used to dig for state-forming insects such as termites . The Alvarezsauridae share a number of characteristics with birds. Her small breastbone (sternum) is provided with a sternum ridge that enlarges the attachment surface for the muscles of the front limbs. As in birds, the carpal and metacarpal bones are fused together ( Carpometacarpus ). In shuvuuia were spring-like structures found.

Systematics

Smaller Alvarezsauridae (Parvicursorinae) in size comparison ( from left to right ):
Parvicursor remotus
Ceratonykus oculatus
Shuvuuia deserti
Mononykus olecranus

The Alvarezsauridae were originally assigned very close to the birds , for example as a sister group of Archeopteryx . However, this notion was relativized by later discovered but more primitive forms such as Haplocheirus , Patagonykus and Alvarezsaurus , which do not show all the bird-like features of the first discovered genera Mononykus and Shuvuuia . The corresponding characteristics could therefore also have developed independently ( convergently ) in birds and the late Alvarezsauriden .

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

literature

Live reconstruction of Linhenykus

Individual evidence

  1. ^ A b Jonah N. Choiniere, Xing Xu, James M. Clark , Catherine A. Forster, Yu Guo, Fenglu Han: A basal alvarezsauroid theropod from the Early Late Jurassic of Xinjiang, China. In: Science . Vol. 327, No. 5965, 2010, pp. 571-574, doi : 10.1126 / science.1182143 .
  2. ^ A b Thomas R. Holtz Jr .: Dinosaurs. Random House, New York NY 2007, ISBN 978-0-375-82419-7 , pp. 136-138.
  3. ^ Alan H. Turner, Sterling J. Nesbitt, Mark A. Norell : A Large Alvarezsaurid from the Late Cretaceous of Mongolia (= American Museum Novitates. No. 3548). American Museum of Natural History, New York NY 2009, digital copy (PDF; 2.97 MB) .

Web links

Commons : Alvarezsauridae  - Collection of images, videos and audio files