Avimimus

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Avimimus
Drawing life reconstruction by Avimimus

Drawing life reconstruction by Avimimus

Temporal occurrence
Upper Cretaceous ( Santonium to early Campanium )
86.3 to 80.6 million years
Locations
Systematics
Theropoda
Coelurosauria
Maniraptora
Oviraptorosauria
Avimimidae
Avimimus
Scientific name of the  family
Avimimidae
Kursanov , 1981
Scientific name of the  genus
Avimimus
Kursanov, 1981
Art
  • Avimimus portentosus Kursanow, 1981
  • Avimimus sp. Ryan, Currie & Russell, 2001

Avimimus is a theropod dinosaur from the group of Oviraptorosauria from the Upper Cretaceous East Asia .

This genus was first described in 1981 by Sergej Kursanow with the species Avimimus portentosus , based on an almost complete skeleton.

Another almost complete skeleton was discovered in 1996. In 2001 a second species ( Avimimus sp.) Was informally described on the basis of a few isolated bones . In 2008, the discovery of a bonebed (sediment layer heavily enriched with fossil bones) was made known that contains the remains of at least 10 Avimimus individuals.

Avimimus was a two-legged theropod about 1.5 meters long, whose jaws formed a mostly toothless beak - this could indicate a herbivorous or omnivorous diet. Kursanow suspects in his first description and subsequent publications that Avimimus could have fed on flying or jumping insects - he sees this way of life as a possible first step towards bird flight, as jumps or similar movements would have been necessary during hunting. It was probably Avimimus. feathered.

features

skull
Graphic reconstruction of the skeleton

The relatively small skull is characterized by relatively large eye sockets and a large brain, which is also indicated by the relatively large bones of the brain skull . Overall, the skull is lightly built, which z. B. points to the very small occipital condyle , the articular knot of the occiput . The foramen magnum , the occipital opening, was relatively large in Avimimus . Despite the light structure, the skull appears very solid, so almost all the bones of the skull roof are fused. Only the intermaxillary bone at the front end of the upper jaw shows small teeth, the rest of the jaw was toothless.

The neck was long and thin, showing at least 12 vertebrae that were longer than other Oviraptorosauria. The sacrum consisted of 7 vertebrae, the pelvis was wide. In contrast to all other Oviraptorosauria, the pelvic bones were fused together, the seams being almost invisible. The arms were short and made up a third of the length of the hind legs. The metacarpal bones were fused, as in today's birds. The legs were long and thin, with the shinbone (tibia) being relatively long. Similar to today's birds, the legs show a tibiotarsus, which means that the upper bones of the foot were fused with the shin. The entire tibiotarsus was 30% longer than the thigh bone (femur), which is 188 mm long in the type specimen . There was also an arctometatarsus: the second and fourth metatarsal bones pushed over the third, so that when viewed from the front it was only visible on the lower part of the metatarsal.

History of discovery and naming

The first fossils of Avimimus were found by a Soviet-Mongolian expedition to the Gobi desert in the summer of 1973. The holotype material (catalog number PIN 3907/1) was discovered in the Udan-Sayr site, in the foothills of the Gurvansaikhan mountains in the south Gobi Desert is located in Mongolia .

The approximately 15 meter thick sediment layer of the site is dominated by reddish sandstones and also contained teeth of the tyrannosaurid Tarbosaurus . Other remains (catalog number 3906/1) come from the Shara-Tsav site in the southeastern Gobi Desert, which is particularly known for an almost complete skeleton of the ornithomimosaur Gallimimus and a skull of the sauropod Nemegtosaurus . Kursanov states in his first description that the Avimimus fossils come from the Djadochta Formation - researchers working with Watabe, who examined a newer skeleton, believe, however, that they belong to the younger Nemegt Formation to be more likely.

The type material from Udan-Sayr is an almost complete skeleton, with only the poorly preserved cranium of the skull being found. Most of the skeleton was anatomically connected when it was discovered; however, all vertebrae, pelvic and upper arm bones were found separate. The finds from Shara-Tsav are post-cranial bones of various individuals. The finds are dated to the Upper Cretaceous ( Santonium to early Campanian ) and are therefore around 86 to 80 million years old.

The finds were first described in 1981 by Sergei Kursanov. Avimimus portentosus means something like "unusual bird imitator", with the generic name Avimimus derived from the Latin words avis (bird) and mimus (imitate), while the specific epithet comes from the Latin portentosus (unusual).

In 2000, Watabe et al. another nearly complete skeleton discovered in 1996. In addition, these authors ascribed a number of small theropod footprints from the area of ​​discovery to Avimimus . A study from 2001 came to the conclusion that various Avimimus bones found in isolation are one or more new species that are provisionally classified as Avimimus sp. be guided.

In 2008, a team of Canadian, American, and Mongolian paleontologists, led by Philip Currie, reported the discovery of an extensive bonebed of Avimimus sp. At least 10 different individuals could be detected, but the deposits could contain other remains. The site belongs to the Nemegt Formation and is 10.5 meters above the Barun-Goyot Formation in the Gobi Desert. All individuals were either adults or subadults, with the adults varying only slightly in size. The adult animals show a stronger fusion of the bones of the tarsometatarsus and the tibiotarsus, and scars, which were created by muscle attachments to the bones, are more clearly visible on the bones of adult animals. The research team also suspects a possible group life, since the individuals were found together.

In 1991, Sankar Chatterjee established the taxon Avimimiformes , but this is not recognized by most paleontologists today, as the group contains only one species.

literature

Individual evidence

  1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 150, (online) ( Memento of the original from July 13, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / press.princeton.edu
  2. ↑ a b c d Сергей М. Курзанов: О необычных тероподах из верхнего мела МНР. In: Совместная советско-монгольская палеонтологическая экспедиция. Труды. Volume 15, 1991, ISSN  0320-2305 , pp. 39-50.
  3. ^ A b Peter Dodson: The Age of Dinosaurs. Publications International, Lincolnwood IL 1993, ISBN 0-7853-0443-6 , p. 130.
  4. ↑ a b Сергей М. Курзанов: Авимимус и проблема происхождения птиц. In: Совместная советско-монгольская палеонтологическая экспедиция. Труды. Volume 24, 1983, pp. 104-109.
  5. ↑ a b c Mahito Watabe, David B. Weishampel, Rinchen Barsbold, Khishigjav Tsogtbaatar, Shigeru Suzuki: New nearly complete skeleton of the bird-like theropod, Avimimus, from the Upper Cretaceous of the Gobi Desert, Mongolia. In: Journal of Vertebrate Paleontology. Volume 20, Supplement to No. 3 = Abstracts of Papers. Sixtieth Annual Meeting Society of Vertebrate Paleontology. Fiesta Americana Reforma Hotel Mexico City, Mexico, October 25-28, 2000. 2000, ISSN  0272-4634 , p. 77A.
  6. ↑ a b Osmólska et al: Oviraptorosauria. 2004, p. 181.
  7. ↑ Osmólska et al .: Oviraptorosauria. 2004, p. 176.
  8. ↑ Mahito Watabe, Shigeru Suzuki, Khishigjav Tsogtbaatar: Geological and geographical distribution of bird-like theropod, Avimimus in Mongolia. In: Journal of Vertebrate Paleontology. Volume 26, Supplement to No. 3 = Abstracts of Papers. Sixty-Sixth Annual Meeting Society of Vertebrate Paleontology. Canadian Museum of Nature, Marriott Ottawa Crowne Plaza Ottawa, Ottawa, Ontario, Canada, October 18-21, 2006. 2006, pp. 136A-137A.
  9. ↑ Michael J. Ryan, Philip J. Currie, Dale A. Russell : New material of Avimimus portentosus (Theropoda) from the Iren Debasu Formation (Upper Cretaceous) of the Erenhot Region of Inner Mongolia. In: Journal of Vertebrate Paleontology. Volume 21, Supplement to No. 3 = Abstracts of Papers Sixty-First Annual Meeting Society of Vertebrate Paleontology. Museum of the Rockies Montana, State University Boseman, Montana, October-3-6, 2001. 2001, p. 95A.
  10. ↑ Philip J. Currie, Nicholas R. Longrich, Michael J. Ryan, David A. Eberth, Badamgarav Demchig: A bonebed of Avimimus sp. (Dinosauria: Theropoda) from the Late Cretaceous Nemegt Formation, Gobi Desert: Insights into social behavior and development in a maniraptoran theropod. In: Journal of Vertebrate Paleontology. Volume 28, Supplement to No. 3 = Program and Abstracts. 68th Annual Meeting Society of Vertebrate Paleontology. Cleveland Museum of Natural History. Case Western Reserve University Renaissance Cleveland Hotel, Cleveland, Ohio USA October 15-18, 2008. 2008, p. 67A.

Web links

Commons : Avimimus  - collection of images, videos and audio files